From c70fe62ed182000e0d627c3b37b6941400f5f537 Mon Sep 17 00:00:00 2001
From: Sergey Biryukov <sergeybiryukov@git.wordpress.org>
Date: Mon, 19 Jul 2021 14:00:11 +0000
Subject: [PATCH] Tests: Replace `assertContains()` with
 `assertStringContainsString()` when used with strings.

Using the `assertContains()` and `assertNotContains()` methods with string haystacks was deprecated in PHPUnit 8 and removed in PHPUnit 9.

While WordPress test suite currently only supports PHPUnit up to 7.5.x, this allows us to switch to newer assertions ahead of adding full support for PHPUnit 8+.

These methods introduced in PHPUnit 7.5 should be used as an alternative:

* `assertStringContainsString()`
* `assertStringContainsStringIgnoringCase`
* `assertStringNotContainsString()`
* `assertStringNotContainsStringIgnoringCase`

As WordPress currently uses PHPUnit 5.7.x to run tests on PHP 5.6, polyfills for these methods were added to the `WP_UnitTestCase` class for PHPUnit < 7.5.

Follow-up to [51331], [51451], [51461].

Props jrf, dd32, SergeyBiryukov.
See #53363, #46149.

git-svn-id: https://develop.svn.wordpress.org/trunk@51462 602fd350-edb4-49c9-b593-d223f7449a82
---
 .../phpunit/tests/admin/includesListTable.php | 46 ++++-----
 tests/phpunit/tests/admin/includesPost.php    | 26 ++---
 .../phpunit/tests/admin/includesTemplate.php  |  8 +-
 .../tests/admin/wpPrivacyRequestsTable.php    |  2 +-
 tests/phpunit/tests/adminbar.php              |  4 +-
 tests/phpunit/tests/ajax/Compression.php      |  6 +-
 tests/phpunit/tests/ajax/CustomizeManager.php | 10 +-
 tests/phpunit/tests/ajax/DimComment.php       |  2 +-
 tests/phpunit/tests/ajax/ReplytoComment.php   |  2 +-
 tests/phpunit/tests/blocks/block-editor.php   | 10 +-
 tests/phpunit/tests/blocks/render.php         |  2 +-
 .../tests/category/wpDropdownCategories.php   | 18 ++--
 .../tests/category/wpListCategories.php       | 84 ++++++++--------
 tests/phpunit/tests/comment-submission.php    | 10 +-
 tests/phpunit/tests/comment.php               |  4 +-
 tests/phpunit/tests/comment/commentForm.php   |  6 +-
 .../tests/comment/commentsTemplate.php        | 10 +-
 .../phpunit/tests/comment/getCommentLink.php  | 14 +--
 .../tests/comment/getCommentReplyLink.php     |  2 +-
 tests/phpunit/tests/comment/query.php         | 44 ++++-----
 tests/phpunit/tests/customize/control.php     | 12 +--
 .../tests/customize/custom-css-setting.php    |  6 +-
 tests/phpunit/tests/customize/manager.php     | 54 +++++-----
 tests/phpunit/tests/customize/nav-menus.php   | 36 +++----
 tests/phpunit/tests/customize/panel.php       | 20 ++--
 tests/phpunit/tests/customize/partial.php     |  2 +-
 tests/phpunit/tests/customize/section.php     | 12 +--
 tests/phpunit/tests/customize/widgets.php     | 32 +++---
 tests/phpunit/tests/date/query.php            |  2 +-
 tests/phpunit/tests/db.php                    | 18 ++--
 tests/phpunit/tests/dependencies/scripts.php  |  4 +-
 tests/phpunit/tests/dependencies/styles.php   |  2 +-
 tests/phpunit/tests/feed/rss2.php             |  2 +-
 tests/phpunit/tests/formatting/Emoji.php      | 16 +--
 .../tests/formatting/MakeClickable.php        |  2 +-
 tests/phpunit/tests/general/paginateLinks.php |  8 +-
 .../phpunit/tests/general/wpResourceHints.php |  2 +-
 tests/phpunit/tests/l10n.php                  | 66 ++++++-------
 .../tests/link/getNextCommentsLink.php        |  4 +-
 .../tests/link/getPreviousCommentsLink.php    |  2 +-
 .../tests/link/getThePrivacyPolicyLink.php    |  4 +-
 tests/phpunit/tests/mail.php                  |  2 +-
 tests/phpunit/tests/media.php                 | 98 +++++++++----------
 tests/phpunit/tests/meta/query.php            |  6 +-
 tests/phpunit/tests/multisite/site.php        |  4 +-
 tests/phpunit/tests/oembed/WpEmbed.php        |  2 +-
 tests/phpunit/tests/oembed/template.php       |  2 +-
 tests/phpunit/tests/post.php                  |  6 +-
 tests/phpunit/tests/post/attachments.php      |  4 +-
 tests/phpunit/tests/post/getPages.php         |  2 +-
 .../tests/post/getPostsByAuthorSql.php        | 36 +++----
 tests/phpunit/tests/post/getTheContent.php    |  4 +-
 tests/phpunit/tests/post/output.php           | 22 ++---
 tests/phpunit/tests/post/query.php            | 58 +++++------
 tests/phpunit/tests/post/template.php         |  8 +-
 ...acyGeneratePersonalDataExportGroupHtml.php | 42 ++++----
 ...vacySendErasureFulfillmentNotification.php | 38 +++----
 .../wpPrivacySendPersonalDataExportEmail.php  | 26 ++---
 ...acySendRequestConfirmationNotification.php | 10 +-
 tests/phpunit/tests/query.php                 |  8 +-
 tests/phpunit/tests/query/dateQuery.php       |  8 +-
 tests/phpunit/tests/query/invalidQueries.php  | 10 +-
 tests/phpunit/tests/query/noFoundRows.php     | 16 +--
 tests/phpunit/tests/query/postStatus.php      | 10 +-
 tests/phpunit/tests/query/results.php         |  6 +-
 tests/phpunit/tests/query/search.php          |  2 +-
 .../rest-api/rest-attachments-controller.php  |  6 +-
 .../rest-block-renderer-controller.php        |  2 +-
 .../rest-api/rest-categories-controller.php   | 16 +--
 .../rest-api/rest-comments-controller.php     | 10 +-
 .../tests/rest-api/rest-pages-controller.php  |  4 +-
 .../tests/rest-api/rest-posts-controller.php  | 14 +--
 .../rest-api/rest-revisions-controller.php    |  6 +-
 .../tests/rest-api/rest-tags-controller.php   | 20 ++--
 .../tests/rest-api/rest-users-controller.php  | 12 +--
 tests/phpunit/tests/rewrite.php               |  2 +-
 tests/phpunit/tests/robots.php                | 16 +--
 tests/phpunit/tests/sitemaps/sitemaps.php     |  8 +-
 tests/phpunit/tests/term/getTermBy.php        |  4 +-
 tests/phpunit/tests/term/getTermLink.php      | 18 ++--
 tests/phpunit/tests/term/query.php            |  4 +-
 .../phpunit/tests/term/wpGenerateTagCloud.php | 18 ++--
 tests/phpunit/tests/theme/customHeader.php    |  6 +-
 tests/phpunit/tests/user.php                  |  8 +-
 tests/phpunit/tests/user/author.php           | 12 +--
 tests/phpunit/tests/user/query.php            | 36 +++----
 tests/phpunit/tests/user/wpDropdownUsers.php  | 24 ++---
 .../phpunit/tests/user/wpSendUserRequest.php  | 40 ++++----
 tests/phpunit/tests/widgets.php               | 46 ++++-----
 .../tests/widgets/custom-html-widget.php      | 22 ++---
 .../tests/widgets/media-audio-widget.php      | 12 +--
 .../tests/widgets/media-gallery-widget.php    | 12 +--
 .../tests/widgets/media-image-widget.php      | 60 ++++++------
 .../tests/widgets/media-video-widget.php      | 24 ++---
 tests/phpunit/tests/widgets/media-widget.php  | 16 +--
 tests/phpunit/tests/widgets/text-widget.php   | 96 +++++++++---------
 tests/phpunit/tests/widgets/wpWidgetRss.php   |  2 +-
 97 files changed, 811 insertions(+), 811 deletions(-)

diff --git a/tests/phpunit/tests/admin/includesListTable.php b/tests/phpunit/tests/admin/includesListTable.php
index eaa496021c..a9f5df0205 100644
--- a/tests/phpunit/tests/admin/includesListTable.php
+++ b/tests/phpunit/tests/admin/includesListTable.php
@@ -221,7 +221,7 @@ class Tests_Admin_includesListTable extends WP_UnitTestCase {
 		$this->assertCount( count( $expected_ids ), array_keys( $matches[0] ) );
 
 		foreach ( $expected_ids as $id ) {
-			$this->assertContains( sprintf( 'id="post-%d"', $id ), $output );
+			$this->assertStringContainsString( sprintf( 'id="post-%d"', $id ), $output );
 		}
 	}
 
@@ -236,7 +236,7 @@ class Tests_Admin_includesListTable extends WP_UnitTestCase {
 		$this->table->extra_tablenav( 'top' );
 		$output = ob_get_clean();
 
-		$this->assertNotContains( 'id="post-query-submit"', $output );
+		$this->assertStringNotContainsString( 'id="post-query-submit"', $output );
 	}
 
 	/**
@@ -250,7 +250,7 @@ class Tests_Admin_includesListTable extends WP_UnitTestCase {
 		$this->table->extra_tablenav( 'top' );
 		$output = ob_get_clean();
 
-		$this->assertNotContains( 'id="filter-by-date"', $output );
+		$this->assertStringNotContainsString( 'id="filter-by-date"', $output );
 	}
 
 	/**
@@ -264,7 +264,7 @@ class Tests_Admin_includesListTable extends WP_UnitTestCase {
 		$this->table->extra_tablenav( 'top' );
 		$output = ob_get_clean();
 
-		$this->assertNotContains( 'id="cat"', $output );
+		$this->assertStringNotContainsString( 'id="cat"', $output );
 	}
 
 	/**
@@ -278,7 +278,7 @@ class Tests_Admin_includesListTable extends WP_UnitTestCase {
 		$this->table->extra_tablenav( 'top' );
 		$output = ob_get_clean();
 
-		$this->assertNotContains( 'id="delete_all"', $output );
+		$this->assertStringNotContainsString( 'id="delete_all"', $output );
 	}
 
 	/**
@@ -291,7 +291,7 @@ class Tests_Admin_includesListTable extends WP_UnitTestCase {
 		$table->extra_tablenav( 'top' );
 		$output = ob_get_clean();
 
-		$this->assertNotContains( 'id="post-query-submit"', $output );
+		$this->assertStringNotContainsString( 'id="post-query-submit"', $output );
 	}
 
 	/**
@@ -313,7 +313,7 @@ class Tests_Admin_includesListTable extends WP_UnitTestCase {
 		$table->extra_tablenav( 'top' );
 		$output = ob_get_clean();
 
-		$this->assertContains( 'id="post-query-submit"', $output );
+		$this->assertStringContainsString( 'id="post-query-submit"', $output );
 	}
 
 	/**
@@ -335,8 +335,8 @@ class Tests_Admin_includesListTable extends WP_UnitTestCase {
 		$table->extra_tablenav( 'top' );
 		$output = ob_get_clean();
 
-		$this->assertContains( 'id="filter-by-comment-type"', $output );
-		$this->assertContains( "<option value='comment'>", $output );
+		$this->assertStringContainsString( 'id="filter-by-comment-type"', $output );
+		$this->assertStringContainsString( "<option value='comment'>", $output );
 	}
 
 	/**
@@ -349,7 +349,7 @@ class Tests_Admin_includesListTable extends WP_UnitTestCase {
 		$table->extra_tablenav( 'top' );
 		$output = ob_get_clean();
 
-		$this->assertNotContains( 'id="delete_all"', $output );
+		$this->assertStringNotContainsString( 'id="delete_all"', $output );
 	}
 
 	/**
@@ -384,7 +384,7 @@ class Tests_Admin_includesListTable extends WP_UnitTestCase {
 OPTIONS;
 		$expected = str_replace( "\r\n", "\n", $expected );
 
-		$this->assertContains( $expected, $output );
+		$this->assertStringContainsString( $expected, $output );
 	}
 
 	/**
@@ -411,14 +411,14 @@ OPTIONS;
 
 		$output = get_echo( array( $object, 'print_column_headers' ) );
 
-		$this->assertContains( '?orderby=comment_author&#038;order=desc', $output, 'Mismatch of the default link ordering for comment author column. Should be desc.' );
-		$this->assertContains( 'column-author sortable asc', $output, 'Mismatch of CSS classes for the comment author column.' );
+		$this->assertStringContainsString( '?orderby=comment_author&#038;order=desc', $output, 'Mismatch of the default link ordering for comment author column. Should be desc.' );
+		$this->assertStringContainsString( 'column-author sortable asc', $output, 'Mismatch of CSS classes for the comment author column.' );
 
-		$this->assertContains( '?orderby=comment_post_ID&#038;order=asc', $output, 'Mismatch of the default link ordering for comment response column. Should be asc.' );
-		$this->assertContains( 'column-response sortable desc', $output, 'Mismatch of CSS classes for the comment post ID column.' );
+		$this->assertStringContainsString( '?orderby=comment_post_ID&#038;order=asc', $output, 'Mismatch of the default link ordering for comment response column. Should be asc.' );
+		$this->assertStringContainsString( 'column-response sortable desc', $output, 'Mismatch of CSS classes for the comment post ID column.' );
 
-		$this->assertContains( '?orderby=comment_date&#038;order=desc', $output, 'Mismatch of the default link ordering for comment date column. Should be asc.' );
-		$this->assertContains( 'column-date sortable asc', $output, 'Mismatch of CSS classes for the comment date column.' );
+		$this->assertStringContainsString( '?orderby=comment_date&#038;order=desc', $output, 'Mismatch of the default link ordering for comment date column. Should be asc.' );
+		$this->assertStringContainsString( 'column-date sortable asc', $output, 'Mismatch of CSS classes for the comment date column.' );
 	}
 
 	/**
@@ -449,14 +449,14 @@ OPTIONS;
 
 		$output = get_echo( array( $object, 'print_column_headers' ) );
 
-		$this->assertContains( '?orderby=comment_author&#038;order=asc', $output, 'Mismatch of the default link ordering for comment author column. Should be asc.' );
-		$this->assertContains( 'column-author sortable desc', $output, 'Mismatch of CSS classes for the comment author column.' );
+		$this->assertStringContainsString( '?orderby=comment_author&#038;order=asc', $output, 'Mismatch of the default link ordering for comment author column. Should be asc.' );
+		$this->assertStringContainsString( 'column-author sortable desc', $output, 'Mismatch of CSS classes for the comment author column.' );
 
-		$this->assertContains( '?orderby=comment_post_ID&#038;order=asc', $output, 'Mismatch of the default link ordering for comment response column. Should be asc.' );
-		$this->assertContains( 'column-response sortable desc', $output, 'Mismatch of CSS classes for the comment post ID column.' );
+		$this->assertStringContainsString( '?orderby=comment_post_ID&#038;order=asc', $output, 'Mismatch of the default link ordering for comment response column. Should be asc.' );
+		$this->assertStringContainsString( 'column-response sortable desc', $output, 'Mismatch of CSS classes for the comment post ID column.' );
 
-		$this->assertContains( '?orderby=comment_date&#038;order=asc', $output, 'Mismatch of the current link ordering for comment date column. Should be asc.' );
-		$this->assertContains( 'column-date sorted desc', $output, 'Mismatch of CSS classes for the comment date column.' );
+		$this->assertStringContainsString( '?orderby=comment_date&#038;order=asc', $output, 'Mismatch of the current link ordering for comment date column. Should be asc.' );
+		$this->assertStringContainsString( 'column-date sorted desc', $output, 'Mismatch of CSS classes for the comment date column.' );
 	}
 
 }
diff --git a/tests/phpunit/tests/admin/includesPost.php b/tests/phpunit/tests/admin/includesPost.php
index 6b65b4beec..1b33aff87c 100644
--- a/tests/phpunit/tests/admin/includesPost.php
+++ b/tests/phpunit/tests/admin/includesPost.php
@@ -391,8 +391,8 @@ class Tests_Admin_Includes_Post extends WP_UnitTestCase {
 		);
 
 		$found = get_sample_permalink_html( $p );
-		$this->assertContains( 'href="' . get_option( 'home' ) . '/?p=' . $p . '"', $found );
-		$this->assertContains( '>' . get_option( 'home' ) . '/?p=' . $p . '<', $found );
+		$this->assertStringContainsString( 'href="' . get_option( 'home' ) . '/?p=' . $p . '"', $found );
+		$this->assertStringContainsString( '>' . get_option( 'home' ) . '/?p=' . $p . '<', $found );
 	}
 
 	/**
@@ -415,8 +415,8 @@ class Tests_Admin_Includes_Post extends WP_UnitTestCase {
 
 		$found = get_sample_permalink_html( $p );
 		$post  = get_post( $p );
-		$this->assertContains( 'href="' . get_option( 'home' ) . '/' . $post->post_name . '/"', $found );
-		$this->assertContains( '>' . urldecode( $post->post_name ) . '<', $found );
+		$this->assertStringContainsString( 'href="' . get_option( 'home' ) . '/' . $post->post_name . '/"', $found );
+		$this->assertStringContainsString( '>' . urldecode( $post->post_name ) . '<', $found );
 	}
 
 	/**
@@ -440,8 +440,8 @@ class Tests_Admin_Includes_Post extends WP_UnitTestCase {
 
 		$found = get_sample_permalink_html( $p );
 		$post  = get_post( $p );
-		$this->assertContains( 'href="' . get_option( 'home' ) . '/' . $post->post_name . '/"', $found );
-		$this->assertContains( '>' . urldecode( get_permalink( $post ) ) . '<', $found );
+		$this->assertStringContainsString( 'href="' . get_option( 'home' ) . '/' . $post->post_name . '/"', $found );
+		$this->assertStringContainsString( '>' . urldecode( get_permalink( $post ) ) . '<', $found );
 	}
 
 	/**
@@ -464,8 +464,8 @@ class Tests_Admin_Includes_Post extends WP_UnitTestCase {
 		$found   = get_sample_permalink_html( $p, null, 'new_slug-صورة' );
 		$post    = get_post( $p );
 		$message = 'Published post';
-		$this->assertContains( 'href="' . get_option( 'home' ) . '/' . $post->post_name . '/"', $found, $message );
-		$this->assertContains( '>new_slug-صورة<', $found, $message );
+		$this->assertStringContainsString( 'href="' . get_option( 'home' ) . '/' . $post->post_name . '/"', $found, $message );
+		$this->assertStringContainsString( '>new_slug-صورة<', $found, $message );
 
 		// Scheduled posts should use published permalink.
 		$future_date = gmdate( 'Y-m-d H:i:s', time() + 100 );
@@ -480,8 +480,8 @@ class Tests_Admin_Includes_Post extends WP_UnitTestCase {
 		$found   = get_sample_permalink_html( $p, null, 'new_slug-صورة' );
 		$post    = get_post( $p );
 		$message = 'Scheduled post';
-		$this->assertContains( 'href="' . get_option( 'home' ) . '/' . $post->post_name . '/"', $found, $message );
-		$this->assertContains( '>new_slug-صورة<', $found, $message );
+		$this->assertStringContainsString( 'href="' . get_option( 'home' ) . '/' . $post->post_name . '/"', $found, $message );
+		$this->assertStringContainsString( '>new_slug-صورة<', $found, $message );
 
 		// Draft posts should use preview link.
 		$p = self::factory()->post->create(
@@ -498,8 +498,8 @@ class Tests_Admin_Includes_Post extends WP_UnitTestCase {
 		$preview_link = get_permalink( $post->ID );
 		$preview_link = add_query_arg( 'preview', 'true', $preview_link );
 
-		$this->assertContains( 'href="' . esc_url( $preview_link ) . '"', $found, $message );
-		$this->assertContains( '>new_slug-صورة<', $found, $message );
+		$this->assertStringContainsString( 'href="' . esc_url( $preview_link ) . '"', $found, $message );
+		$this->assertStringContainsString( '>new_slug-صورة<', $found, $message );
 	}
 
 	/**
@@ -522,7 +522,7 @@ class Tests_Admin_Includes_Post extends WP_UnitTestCase {
 
 		$found = get_sample_permalink_html( $p );
 		$post  = get_post( $p );
-		$this->assertContains( 'href="' . esc_url( get_preview_post_link( $post ) ), $found );
+		$this->assertStringContainsString( 'href="' . esc_url( get_preview_post_link( $post ) ), $found );
 	}
 
 	/**
diff --git a/tests/phpunit/tests/admin/includesTemplate.php b/tests/phpunit/tests/admin/includesTemplate.php
index 48c5accf77..7a7b5ccd40 100644
--- a/tests/phpunit/tests/admin/includesTemplate.php
+++ b/tests/phpunit/tests/admin/includesTemplate.php
@@ -17,7 +17,7 @@ class Tests_Admin_includesTemplate extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( "checked='checked'", $output );
+		$this->assertStringContainsString( "checked='checked'", $output );
 	}
 
 	/**
@@ -33,7 +33,7 @@ class Tests_Admin_includesTemplate extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( 'class="popular-category"', $output );
+		$this->assertStringContainsString( 'class="popular-category"', $output );
 	}
 
 	public function data_wp_terms_checklist_with_selected_cats() {
@@ -185,8 +185,8 @@ class Tests_Admin_includesTemplate extends WP_UnitTestCase {
 
 		$expected = sprintf( 'notice %s settings-error is-dismissible', $expected );
 
-		$this->assertContains( $expected, $output );
-		$this->assertNotContains( 'notice-notice-', $output );
+		$this->assertStringContainsString( $expected, $output );
+		$this->assertStringNotContainsString( 'notice-notice-', $output );
 	}
 
 	public function settings_errors_css_classes_provider() {
diff --git a/tests/phpunit/tests/admin/wpPrivacyRequestsTable.php b/tests/phpunit/tests/admin/wpPrivacyRequestsTable.php
index d854f7b145..1b7eeca526 100644
--- a/tests/phpunit/tests/admin/wpPrivacyRequestsTable.php
+++ b/tests/phpunit/tests/admin/wpPrivacyRequestsTable.php
@@ -82,7 +82,7 @@ class Tests_Admin_wpPrivacyRequestsTable extends WP_UnitTestCase {
 		unset( $_REQUEST['orderby'] );
 		unset( $_REQUEST['s'] );
 
-		$this->assertContains( "ORDER BY {$wpdb->posts}.{$expected}", $this->sql );
+		$this->assertStringContainsString( "ORDER BY {$wpdb->posts}.{$expected}", $this->sql );
 	}
 
 	/**
diff --git a/tests/phpunit/tests/adminbar.php b/tests/phpunit/tests/adminbar.php
index 365094f454..ae24c8201c 100644
--- a/tests/phpunit/tests/adminbar.php
+++ b/tests/phpunit/tests/adminbar.php
@@ -264,7 +264,7 @@ class Tests_AdminBar extends WP_UnitTestCase {
 		$admin_bar = new WP_Admin_Bar();
 		$admin_bar->add_node( $node_data );
 		$admin_bar_html = get_echo( array( $admin_bar, 'render' ) );
-		$this->assertContains( $expected_html, $admin_bar_html );
+		$this->assertStringContainsString( $expected_html, $admin_bar_html );
 	}
 
 	/**
@@ -678,7 +678,7 @@ class Tests_AdminBar extends WP_UnitTestCase {
 		$query_params = array();
 		wp_parse_str( $parsed_url['query'], $query_params );
 		$this->assertSame( $uuid, $query_params['changeset_uuid'] );
-		$this->assertNotContains( 'changeset_uuid', $query_params['url'] );
+		$this->assertStringNotContainsString( 'changeset_uuid', $query_params['url'] );
 	}
 
 	/**
diff --git a/tests/phpunit/tests/ajax/Compression.php b/tests/phpunit/tests/ajax/Compression.php
index a059e5c729..e900b85375 100644
--- a/tests/phpunit/tests/ajax/Compression.php
+++ b/tests/phpunit/tests/ajax/Compression.php
@@ -49,7 +49,7 @@ class Tests_Ajax_CompressionTest extends WP_Ajax_UnitTestCase {
 		}
 
 		// Ensure we found the right match.
-		$this->assertContains( 'wpCompressionTest', $this->_last_response );
+		$this->assertStringContainsString( 'wpCompressionTest', $this->_last_response );
 	}
 
 	/**
@@ -74,7 +74,7 @@ class Tests_Ajax_CompressionTest extends WP_Ajax_UnitTestCase {
 		}
 
 		// Ensure we found the right match.
-		$this->assertContains( 'wpCompressionTest', gzinflate( $this->_last_response ) );
+		$this->assertStringContainsString( 'wpCompressionTest', gzinflate( $this->_last_response ) );
 	}
 
 	/**
@@ -99,7 +99,7 @@ class Tests_Ajax_CompressionTest extends WP_Ajax_UnitTestCase {
 		}
 
 		// Ensure we found the right match.
-		$this->assertContains( 'wpCompressionTest', $this->_gzdecode( $this->_last_response ) );
+		$this->assertStringContainsString( 'wpCompressionTest', $this->_gzdecode( $this->_last_response ) );
 	}
 
 	/**
diff --git a/tests/phpunit/tests/ajax/CustomizeManager.php b/tests/phpunit/tests/ajax/CustomizeManager.php
index d6ce045da2..5dabb44412 100644
--- a/tests/phpunit/tests/ajax/CustomizeManager.php
+++ b/tests/phpunit/tests/ajax/CustomizeManager.php
@@ -474,8 +474,8 @@ class Tests_Ajax_CustomizeManager extends WP_Ajax_UnitTestCase {
 		$autosave_revision = wp_get_post_autosave( $post_id );
 		$this->assertInstanceOf( 'WP_Post', $autosave_revision );
 
-		$this->assertContains( 'New Site Title', get_post( $post_id )->post_content );
-		$this->assertContains( 'Autosaved Site Title', $autosave_revision->post_content );
+		$this->assertStringContainsString( 'New Site Title', get_post( $post_id )->post_content );
+		$this->assertStringContainsString( 'Autosaved Site Title', $autosave_revision->post_content );
 	}
 
 	/**
@@ -679,7 +679,7 @@ class Tests_Ajax_CustomizeManager extends WP_Ajax_UnitTestCase {
 		$_REQUEST['dismiss_autosave'] = true;
 		$this->assertNotWPError( $r );
 		$this->assertFalse( wp_get_post_autosave( $wp_customize->changeset_post_id() ) );
-		$this->assertContains( 'Foo', get_post( $wp_customize->changeset_post_id() )->post_content );
+		$this->assertStringContainsString( 'Foo', get_post( $wp_customize->changeset_post_id() )->post_content );
 
 		// Since no autosave yet, confirm no action.
 		$this->make_ajax_call( 'customize_dismiss_autosave_or_lock' );
@@ -700,8 +700,8 @@ class Tests_Ajax_CustomizeManager extends WP_Ajax_UnitTestCase {
 		$this->assertNotWPError( $r );
 		$autosave_revision = wp_get_post_autosave( $wp_customize->changeset_post_id() );
 		$this->assertInstanceOf( 'WP_Post', $autosave_revision );
-		$this->assertContains( 'Foo', get_post( $wp_customize->changeset_post_id() )->post_content );
-		$this->assertContains( 'Bar', $autosave_revision->post_content );
+		$this->assertStringContainsString( 'Foo', get_post( $wp_customize->changeset_post_id() )->post_content );
+		$this->assertStringContainsString( 'Bar', $autosave_revision->post_content );
 
 		// Confirm autosave gets deleted.
 		$this->make_ajax_call( 'customize_dismiss_autosave_or_lock' );
diff --git a/tests/phpunit/tests/ajax/DimComment.php b/tests/phpunit/tests/ajax/DimComment.php
index 9ff1bf405e..89fda6110e 100644
--- a/tests/phpunit/tests/ajax/DimComment.php
+++ b/tests/phpunit/tests/ajax/DimComment.php
@@ -197,7 +197,7 @@ class Tests_Ajax_DimComment extends WP_Ajax_UnitTestCase {
 			// Ensure everything is correct.
 			$this->assertSame( '0', (string) $xml->response[0]->comment['id'] );
 			$this->assertSame( 'dim-comment_0', (string) $xml->response['action'] );
-			$this->assertContains( 'Comment ' . $_POST['id'] . ' does not exist', $this->_last_response );
+			$this->assertStringContainsString( 'Comment ' . $_POST['id'] . ' does not exist', $this->_last_response );
 
 		} catch ( Exception $e ) {
 			$this->fail( 'Unexpected exception type: ' . get_class( $e ) );
diff --git a/tests/phpunit/tests/ajax/ReplytoComment.php b/tests/phpunit/tests/ajax/ReplytoComment.php
index dbc8b3bfef..f69b3e1fc2 100644
--- a/tests/phpunit/tests/ajax/ReplytoComment.php
+++ b/tests/phpunit/tests/ajax/ReplytoComment.php
@@ -219,7 +219,7 @@ class Tests_Ajax_ReplytoComment extends WP_Ajax_UnitTestCase {
 			$this->fail();
 		} catch ( WPAjaxDieStopException $e ) {
 			$wpdb->suppress_errors( false );
-			$this->assertContains( '1', $e->getMessage() );
+			$this->assertStringContainsString( '1', $e->getMessage() );
 		}
 	}
 
diff --git a/tests/phpunit/tests/blocks/block-editor.php b/tests/phpunit/tests/blocks/block-editor.php
index 7baabe3ae2..c9f1ac843b 100644
--- a/tests/phpunit/tests/blocks/block-editor.php
+++ b/tests/phpunit/tests/blocks/block-editor.php
@@ -435,7 +435,7 @@ class WP_Test_Block_Editor extends WP_UnitTestCase {
 		block_editor_rest_api_preload( array(), $editor_context );
 
 		$after = implode( '', wp_scripts()->registered['wp-api-fetch']->extra['after'] );
-		$this->assertNotContains( 'wp.apiFetch.createPreloadingMiddleware', $after );
+		$this->assertStringNotContainsString( 'wp.apiFetch.createPreloadingMiddleware', $after );
 	}
 
 	/**
@@ -462,7 +462,7 @@ class WP_Test_Block_Editor extends WP_UnitTestCase {
 		remove_filter( 'block_editor_preload_paths', 'filter_remove_preload_paths' );
 
 		$after = implode( '', wp_scripts()->registered['wp-api-fetch']->extra['after'] );
-		$this->assertNotContains( 'wp.apiFetch.createPreloadingMiddleware', $after );
+		$this->assertStringNotContainsString( 'wp.apiFetch.createPreloadingMiddleware', $after );
 	}
 
 	/**
@@ -489,9 +489,9 @@ class WP_Test_Block_Editor extends WP_UnitTestCase {
 		remove_filter( 'block_editor_rest_api_preload_paths', 'filter_add_preload_paths' );
 
 		$after = implode( '', wp_scripts()->registered['wp-api-fetch']->extra['after'] );
-		$this->assertContains( 'wp.apiFetch.createPreloadingMiddleware', $after );
-		$this->assertContains( '"\/wp\/v2\/blocks"', $after );
-		$this->assertContains( '"\/wp\/v2\/types"', $after );
+		$this->assertStringContainsString( 'wp.apiFetch.createPreloadingMiddleware', $after );
+		$this->assertStringContainsString( '"\/wp\/v2\/blocks"', $after );
+		$this->assertStringContainsString( '"\/wp\/v2\/types"', $after );
 	}
 
 	/**
diff --git a/tests/phpunit/tests/blocks/render.php b/tests/phpunit/tests/blocks/render.php
index b22b8495db..db449c3a20 100644
--- a/tests/phpunit/tests/blocks/render.php
+++ b/tests/phpunit/tests/blocks/render.php
@@ -304,7 +304,7 @@ class WP_Test_Block_Render extends WP_UnitTestCase {
 		);
 		$comments = do_blocks( '<!-- wp:latest-comments {"commentsToShow":1,"displayExcerpt":true} /-->' );
 
-		$this->assertNotContains( $comment_text, $comments );
+		$this->assertStringNotContainsString( $comment_text, $comments );
 	}
 
 	/**
diff --git a/tests/phpunit/tests/category/wpDropdownCategories.php b/tests/phpunit/tests/category/wpDropdownCategories.php
index 0b38c23889..92200a21e3 100644
--- a/tests/phpunit/tests/category/wpDropdownCategories.php
+++ b/tests/phpunit/tests/category/wpDropdownCategories.php
@@ -25,7 +25,7 @@ class Tests_Category_WpDropdownCategories extends WP_UnitTestCase {
 		);
 
 		// Test to see if it returns the default with the category ID.
-		$this->assertContains( 'value="' . $cat_id . '"', $dropdown_default );
+		$this->assertStringContainsString( 'value="' . $cat_id . '"', $dropdown_default );
 	}
 
 	/**
@@ -50,7 +50,7 @@ class Tests_Category_WpDropdownCategories extends WP_UnitTestCase {
 		);
 
 		// Test to see if it returns the default with the category ID.
-		$this->assertContains( 'value="' . $cat_id . '"', $found );
+		$this->assertStringContainsString( 'value="' . $cat_id . '"', $found );
 	}
 
 	/**
@@ -75,7 +75,7 @@ class Tests_Category_WpDropdownCategories extends WP_UnitTestCase {
 		);
 
 		// Test to see if it returns the default with the category slug.
-		$this->assertContains( 'value="test_category"', $found );
+		$this->assertStringContainsString( 'value="test_category"', $found );
 	}
 
 	/**
@@ -100,7 +100,7 @@ class Tests_Category_WpDropdownCategories extends WP_UnitTestCase {
 		);
 
 		// Test to see if it returns the default with the category slug.
-		$this->assertContains( 'value="' . $cat_id . '"', $found );
+		$this->assertStringContainsString( 'value="' . $cat_id . '"', $found );
 	}
 
 	/**
@@ -130,7 +130,7 @@ class Tests_Category_WpDropdownCategories extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( 'value="test_category_2" selected="selected"', $found );
+		$this->assertStringContainsString( 'value="test_category_2" selected="selected"', $found );
 	}
 
 	/**
@@ -148,11 +148,11 @@ class Tests_Category_WpDropdownCategories extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( "value='0' selected='selected'", $found );
+		$this->assertStringContainsString( "value='0' selected='selected'", $found );
 
 		foreach ( $cats as $cat ) {
 			$_cat = get_term( $cat, 'category' );
-			$this->assertNotContains( 'value="' . $_cat->slug . '" selected="selected"', $found );
+			$this->assertStringNotContainsString( 'value="' . $_cat->slug . '" selected="selected"', $found );
 		}
 	}
 
@@ -172,11 +172,11 @@ class Tests_Category_WpDropdownCategories extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( "value='0' selected='selected'", $found );
+		$this->assertStringContainsString( "value='0' selected='selected'", $found );
 
 		foreach ( $cats as $cat ) {
 			$_cat = get_term( $cat, 'category' );
-			$this->assertNotContains( 'value="' . $_cat->slug . '" selected="selected"', $found );
+			$this->assertStringNotContainsString( 'value="' . $_cat->slug . '" selected="selected"', $found );
 		}
 	}
 
diff --git a/tests/phpunit/tests/category/wpListCategories.php b/tests/phpunit/tests/category/wpListCategories.php
index 4d75b4ac00..b3b5b0bafd 100644
--- a/tests/phpunit/tests/category/wpListCategories.php
+++ b/tests/phpunit/tests/category/wpListCategories.php
@@ -14,7 +14,7 @@ class Tests_Category_WpListCategories extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( 'class="cat-item cat-item-' . $c . '"', $found );
+		$this->assertStringContainsString( 'class="cat-item cat-item-' . $c . '"', $found );
 	}
 
 	public function test_class_containing_current_cat() {
@@ -96,11 +96,11 @@ class Tests_Category_WpListCategories extends WP_UnitTestCase {
 		);
 		remove_filter( 'list_cats', array( $this, 'list_cats_callback' ) );
 
-		$this->assertContains( "cat-item-$c2", $found );
-		$this->assertContains( 'Test Cat 2', $found );
+		$this->assertStringContainsString( "cat-item-$c2", $found );
+		$this->assertStringContainsString( 'Test Cat 2', $found );
 
-		$this->assertNotContains( "cat-item-$c1", $found );
-		$this->assertNotContains( 'Test Cat 1', $found );
+		$this->assertStringNotContainsString( "cat-item-$c1", $found );
+		$this->assertStringNotContainsString( 'Test Cat 1', $found );
 	}
 
 	public function list_cats_callback( $cat ) {
@@ -128,8 +128,8 @@ class Tests_Category_WpListCategories extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( "cat-item-$c", $found );
-		$this->assertContains( '0', $found );
+		$this->assertStringContainsString( "cat-item-$c", $found );
+		$this->assertStringContainsString( '0', $found );
 	}
 
 	public function test_show_option_all_link_should_go_to_home_page_when_show_on_front_is_false() {
@@ -144,7 +144,7 @@ class Tests_Category_WpListCategories extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( "<li class='cat-item-all'><a href='" . home_url( '/' ) . "'>All</a></li>", $found );
+		$this->assertStringContainsString( "<li class='cat-item-all'><a href='" . home_url( '/' ) . "'>All</a></li>", $found );
 	}
 
 	public function test_show_option_all_link_should_respect_page_for_posts() {
@@ -163,7 +163,7 @@ class Tests_Category_WpListCategories extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( "<li class='cat-item-all'><a href='" . get_permalink( $p ) . "'>All</a></li>", $found );
+		$this->assertStringContainsString( "<li class='cat-item-all'><a href='" . get_permalink( $p ) . "'>All</a></li>", $found );
 	}
 
 	/**
@@ -192,7 +192,7 @@ class Tests_Category_WpListCategories extends WP_UnitTestCase {
 
 		$pt_archive = get_post_type_archive_link( 'wptests_pt' );
 
-		$this->assertContains( "<li class='cat-item-all'><a href='" . $pt_archive . "'>All</a></li>", $found );
+		$this->assertStringContainsString( "<li class='cat-item-all'><a href='" . $pt_archive . "'>All</a></li>", $found );
 	}
 
 	/**
@@ -221,7 +221,7 @@ class Tests_Category_WpListCategories extends WP_UnitTestCase {
 
 		$pt_archive = get_post_type_archive_link( 'wptests_pt2' );
 
-		$this->assertContains( "<li class='cat-item-all'><a href='" . $pt_archive . "'>All</a></li>", $found );
+		$this->assertStringContainsString( "<li class='cat-item-all'><a href='" . $pt_archive . "'>All</a></li>", $found );
 	}
 
 	public function test_show_option_all_link_should_link_to_post_archive_if_available() {
@@ -247,7 +247,7 @@ class Tests_Category_WpListCategories extends WP_UnitTestCase {
 
 		$url = home_url( '/' );
 
-		$this->assertContains( "<li class='cat-item-all'><a href='" . $url . "'>All</a></li>", $found );
+		$this->assertStringContainsString( "<li class='cat-item-all'><a href='" . $url . "'>All</a></li>", $found );
 	}
 
 	public function test_show_option_all_link_should_link_to_post_archive_if_no_associated_post_types_have_archives() {
@@ -273,7 +273,7 @@ class Tests_Category_WpListCategories extends WP_UnitTestCase {
 
 		$url = home_url( '/' );
 
-		$this->assertContains( "<li class='cat-item-all'><a href='" . $url . "'>All</a></li>", $found );
+		$this->assertStringContainsString( "<li class='cat-item-all'><a href='" . $url . "'>All</a></li>", $found );
 	}
 
 	/**
@@ -286,7 +286,7 @@ class Tests_Category_WpListCategories extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( '<li class="categories">Categories', $found );
+		$this->assertStringContainsString( '<li class="categories">Categories', $found );
 	}
 
 	/**
@@ -300,7 +300,7 @@ class Tests_Category_WpListCategories extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertNotContains( '<li class="categories">Categories', $found );
+		$this->assertStringNotContainsString( '<li class="categories">Categories', $found );
 	}
 
 	/**
@@ -314,7 +314,7 @@ class Tests_Category_WpListCategories extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( '<li class="categories">Categories', $found );
+		$this->assertStringContainsString( '<li class="categories">Categories', $found );
 	}
 
 	/**
@@ -331,7 +331,7 @@ class Tests_Category_WpListCategories extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( '<li class="categories">Categories', $found );
+		$this->assertStringContainsString( '<li class="categories">Categories', $found );
 	}
 
 	/**
@@ -349,7 +349,7 @@ class Tests_Category_WpListCategories extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertNotContains( '</ul></li>', $found );
+		$this->assertStringNotContainsString( '</ul></li>', $found );
 	}
 
 	/**
@@ -379,9 +379,9 @@ class Tests_Category_WpListCategories extends WP_UnitTestCase {
 
 		$actual = wp_list_categories( $args );
 
-		$this->assertNotContains( '<li class="cat-item cat-item-' . $parent . '">', $actual );
+		$this->assertStringNotContainsString( '<li class="cat-item cat-item-' . $parent . '">', $actual );
 
-		$this->assertNotContains( '<li class="cat-item cat-item-' . $child . '">', $actual );
+		$this->assertStringNotContainsString( '<li class="cat-item cat-item-' . $child . '">', $actual );
 	}
 
 	/**
@@ -431,11 +431,11 @@ class Tests_Category_WpListCategories extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertNotContains( '<li class="cat-item cat-item-' . $parent . '">', $actual );
-		$this->assertNotContains( '<li class="cat-item cat-item-' . $parent2 . '">', $actual );
-		$this->assertNotContains( '<li class="cat-item cat-item-' . $child . '">', $actual );
+		$this->assertStringNotContainsString( '<li class="cat-item cat-item-' . $parent . '">', $actual );
+		$this->assertStringNotContainsString( '<li class="cat-item cat-item-' . $parent2 . '">', $actual );
+		$this->assertStringNotContainsString( '<li class="cat-item cat-item-' . $child . '">', $actual );
 
-		$this->assertNotContains( '<li class="cat-item cat-item-' . $child2 . '">', $actual );
+		$this->assertStringNotContainsString( '<li class="cat-item cat-item-' . $child2 . '">', $actual );
 	}
 
 	/**
@@ -511,17 +511,17 @@ class Tests_Category_WpListCategories extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( '<li class="cat-item cat-item-' . $c . '">', $actual );
+		$this->assertStringContainsString( '<li class="cat-item cat-item-' . $c . '">', $actual );
 
-		$this->assertNotContains( '<li class="cat-item cat-item-' . $parent . '">', $actual );
-		$this->assertNotContains( '<li class="cat-item cat-item-' . $parent2 . '">', $actual );
-		$this->assertNotContains( '<li class="cat-item cat-item-' . $child . '">', $actual );
-		$this->assertNotContains( '<li class="cat-item cat-item-' . $child2 . '">', $actual );
+		$this->assertStringNotContainsString( '<li class="cat-item cat-item-' . $parent . '">', $actual );
+		$this->assertStringNotContainsString( '<li class="cat-item cat-item-' . $parent2 . '">', $actual );
+		$this->assertStringNotContainsString( '<li class="cat-item cat-item-' . $child . '">', $actual );
+		$this->assertStringNotContainsString( '<li class="cat-item cat-item-' . $child2 . '">', $actual );
 
-		$this->assertNotContains( '<li class="cat-item cat-item-' . $parent3 . '">', $actual );
-		$this->assertNotContains( '<li class="cat-item cat-item-' . $parent4 . '">', $actual );
-		$this->assertNotContains( '<li class="cat-item cat-item-' . $child3 . '">', $actual );
-		$this->assertNotContains( '<li class="cat-item cat-item-' . $child4 . '">', $actual );
+		$this->assertStringNotContainsString( '<li class="cat-item cat-item-' . $parent3 . '">', $actual );
+		$this->assertStringNotContainsString( '<li class="cat-item cat-item-' . $parent4 . '">', $actual );
+		$this->assertStringNotContainsString( '<li class="cat-item cat-item-' . $child3 . '">', $actual );
+		$this->assertStringNotContainsString( '<li class="cat-item cat-item-' . $child4 . '">', $actual );
 	}
 
 	/**
@@ -597,17 +597,17 @@ class Tests_Category_WpListCategories extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( '<li class="cat-item cat-item-' . $c . '">', $actual );
+		$this->assertStringContainsString( '<li class="cat-item cat-item-' . $c . '">', $actual );
 
-		$this->assertNotContains( '<li class="cat-item cat-item-' . $parent . '">', $actual );
-		$this->assertNotContains( '<li class="cat-item cat-item-' . $parent2 . '">', $actual );
-		$this->assertNotContains( '<li class="cat-item cat-item-' . $child . '">', $actual );
-		$this->assertNotContains( '<li class="cat-item cat-item-' . $child2 . '">', $actual );
+		$this->assertStringNotContainsString( '<li class="cat-item cat-item-' . $parent . '">', $actual );
+		$this->assertStringNotContainsString( '<li class="cat-item cat-item-' . $parent2 . '">', $actual );
+		$this->assertStringNotContainsString( '<li class="cat-item cat-item-' . $child . '">', $actual );
+		$this->assertStringNotContainsString( '<li class="cat-item cat-item-' . $child2 . '">', $actual );
 
-		$this->assertNotContains( '<li class="cat-item cat-item-' . $parent3 . '">', $actual );
-		$this->assertNotContains( '<li class="cat-item cat-item-' . $parent4 . '">', $actual );
-		$this->assertNotContains( '<li class="cat-item cat-item-' . $child3 . '">', $actual );
-		$this->assertNotContains( '<li class="cat-item cat-item-' . $child4 . '">', $actual );
+		$this->assertStringNotContainsString( '<li class="cat-item cat-item-' . $parent3 . '">', $actual );
+		$this->assertStringNotContainsString( '<li class="cat-item cat-item-' . $parent4 . '">', $actual );
+		$this->assertStringNotContainsString( '<li class="cat-item cat-item-' . $child3 . '">', $actual );
+		$this->assertStringNotContainsString( '<li class="cat-item cat-item-' . $child4 . '">', $actual );
 	}
 
 	/**
diff --git a/tests/phpunit/tests/comment-submission.php b/tests/phpunit/tests/comment-submission.php
index 56f06b8148..52dcfb43b5 100644
--- a/tests/phpunit/tests/comment-submission.php
+++ b/tests/phpunit/tests/comment-submission.php
@@ -440,7 +440,7 @@ class Tests_Comment_Submission extends WP_UnitTestCase {
 
 		$this->assertNotWPError( $comment );
 		$this->assertInstanceOf( 'WP_Comment', $comment );
-		$this->assertNotContains( '<script', $comment->comment_content );
+		$this->assertStringNotContainsString( '<script', $comment->comment_content );
 
 	}
 
@@ -458,7 +458,7 @@ class Tests_Comment_Submission extends WP_UnitTestCase {
 
 		$this->assertNotWPError( $comment );
 		$this->assertInstanceOf( 'WP_Comment', $comment );
-		$this->assertNotContains( '<script', $comment->comment_content );
+		$this->assertStringNotContainsString( '<script', $comment->comment_content );
 
 	}
 
@@ -482,7 +482,7 @@ class Tests_Comment_Submission extends WP_UnitTestCase {
 
 		$this->assertNotWPError( $comment );
 		$this->assertInstanceOf( 'WP_Comment', $comment );
-		$this->assertNotContains( '<script', $comment->comment_content );
+		$this->assertStringNotContainsString( '<script', $comment->comment_content );
 
 	}
 
@@ -514,7 +514,7 @@ class Tests_Comment_Submission extends WP_UnitTestCase {
 
 		$this->assertNotWPError( $comment );
 		$this->assertInstanceOf( 'WP_Comment', $comment );
-		$this->assertContains( '<script', $comment->comment_content );
+		$this->assertStringContainsString( '<script', $comment->comment_content );
 
 	}
 
@@ -538,7 +538,7 @@ class Tests_Comment_Submission extends WP_UnitTestCase {
 
 		$this->assertNotWPError( $comment );
 		$this->assertInstanceOf( 'WP_Comment', $comment );
-		$this->assertNotContains( '<script', $comment->comment_content );
+		$this->assertStringNotContainsString( '<script', $comment->comment_content );
 
 	}
 
diff --git a/tests/phpunit/tests/comment.php b/tests/phpunit/tests/comment.php
index e9bebe6f63..ffab40df1e 100644
--- a/tests/phpunit/tests/comment.php
+++ b/tests/phpunit/tests/comment.php
@@ -515,7 +515,7 @@ class Tests_Comment extends WP_UnitTestCase {
 		wp_new_comment_notify_postauthor( $c2 );
 		remove_filter( 'comment_notification_text', array( $this, 'save_comment_notification_text' ) );
 
-		$this->assertContains( admin_url( "comment.php?action=editcomment&c={$c1}" ), self::$notify_message );
+		$this->assertStringContainsString( admin_url( "comment.php?action=editcomment&c={$c1}" ), self::$notify_message );
 	}
 
 	/**
@@ -540,7 +540,7 @@ class Tests_Comment extends WP_UnitTestCase {
 		wp_new_comment_notify_moderator( $c2 );
 		remove_filter( 'comment_moderation_text', array( $this, 'save_comment_notification_text' ) );
 
-		$this->assertContains( admin_url( "comment.php?action=editcomment&c={$c1}" ), self::$notify_message );
+		$this->assertStringContainsString( admin_url( "comment.php?action=editcomment&c={$c1}" ), self::$notify_message );
 	}
 
 	/**
diff --git a/tests/phpunit/tests/comment/commentForm.php b/tests/phpunit/tests/comment/commentForm.php
index a03801438d..1b8c8693b4 100644
--- a/tests/phpunit/tests/comment/commentForm.php
+++ b/tests/phpunit/tests/comment/commentForm.php
@@ -35,7 +35,7 @@ class Tests_Comment_CommentForm extends WP_UnitTestCase {
 		$form = get_echo( 'comment_form', array( $args, $p ) );
 
 		$button = '<input name="custom-foo-name" type="submit" id="custom-foo-id" class="custom-foo-class" value="custom-foo-label" />';
-		$this->assertContains( $button, $form );
+		$this->assertStringContainsString( $button, $form );
 	}
 
 	public function test_custom_submit_field() {
@@ -113,7 +113,7 @@ class Tests_Comment_CommentForm extends WP_UnitTestCase {
 
 		$form_with_aria = get_echo( 'comment_form', array( array(), $p ) );
 
-		$this->assertContains( 'aria-describedby="email-notes"', $form_with_aria );
+		$this->assertStringContainsString( 'aria-describedby="email-notes"', $form_with_aria );
 
 		$args = array(
 			'comment_notes_before' => '',
@@ -121,6 +121,6 @@ class Tests_Comment_CommentForm extends WP_UnitTestCase {
 
 		$form_without_aria = get_echo( 'comment_form', array( $args, $p ) );
 
-		$this->assertNotContains( 'aria-describedby="email-notes"', $form_without_aria );
+		$this->assertStringNotContainsString( 'aria-describedby="email-notes"', $form_without_aria );
 	}
 }
diff --git a/tests/phpunit/tests/comment/commentsTemplate.php b/tests/phpunit/tests/comment/commentsTemplate.php
index 5aff968ae1..c0cee5dc74 100644
--- a/tests/phpunit/tests/comment/commentsTemplate.php
+++ b/tests/phpunit/tests/comment/commentsTemplate.php
@@ -558,7 +558,7 @@ class Tests_Comment_CommentsTemplate extends WP_UnitTestCase {
 
 		// This is the main post page, so we don't expect any cpage param.
 		foreach ( $matches[1] as $m ) {
-			$this->assertNotContains( 'cpage', $m );
+			$this->assertStringNotContainsString( 'cpage', $m );
 		}
 
 		$link_p2 = add_query_arg(
@@ -578,7 +578,7 @@ class Tests_Comment_CommentsTemplate extends WP_UnitTestCase {
 
 		// They should all be on page 2.
 		foreach ( $matches[1] as $m ) {
-			$this->assertContains( 'cpage=2', $m );
+			$this->assertStringContainsString( 'cpage=2', $m );
 		}
 	}
 
@@ -650,7 +650,7 @@ class Tests_Comment_CommentsTemplate extends WP_UnitTestCase {
 		preg_match_all( '|href="(.*?#comment-([0-9]+))|', $found_p0, $matches );
 
 		foreach ( $matches[1] as $m ) {
-			$this->assertContains( 'cpage=3', $m );
+			$this->assertStringContainsString( 'cpage=3', $m );
 		}
 
 		$link_p2 = add_query_arg(
@@ -670,7 +670,7 @@ class Tests_Comment_CommentsTemplate extends WP_UnitTestCase {
 
 		// They should all be on page 2.
 		foreach ( $matches[1] as $m ) {
-			$this->assertContains( 'cpage=2', $m );
+			$this->assertStringContainsString( 'cpage=2', $m );
 		}
 
 		// p1 is the last page (neat!).
@@ -691,7 +691,7 @@ class Tests_Comment_CommentsTemplate extends WP_UnitTestCase {
 
 		// They should all be on page 2.
 		foreach ( $matches[1] as $m ) {
-			$this->assertContains( 'cpage=1', $m );
+			$this->assertStringContainsString( 'cpage=1', $m );
 		}
 	}
 
diff --git a/tests/phpunit/tests/comment/getCommentLink.php b/tests/phpunit/tests/comment/getCommentLink.php
index 39551e0aa2..fcb51c2c5b 100644
--- a/tests/phpunit/tests/comment/getCommentLink.php
+++ b/tests/phpunit/tests/comment/getCommentLink.php
@@ -66,7 +66,7 @@ class Tests_Comment_GetCommentLink extends WP_UnitTestCase {
 
 		$found = get_comment_link( self::$comments[1] );
 
-		$this->assertContains( 'cpage=3', $found );
+		$this->assertStringContainsString( 'cpage=3', $found );
 	}
 
 	/**
@@ -79,7 +79,7 @@ class Tests_Comment_GetCommentLink extends WP_UnitTestCase {
 
 		$found = get_comment_link( self::$comments[3] );
 
-		$this->assertContains( 'cpage=2', $found );
+		$this->assertStringContainsString( 'cpage=2', $found );
 	}
 
 	/**
@@ -92,7 +92,7 @@ class Tests_Comment_GetCommentLink extends WP_UnitTestCase {
 
 		$found = get_comment_link( self::$comments[5] );
 
-		$this->assertContains( 'cpage=1', $found );
+		$this->assertStringContainsString( 'cpage=1', $found );
 	}
 
 	/**
@@ -104,7 +104,7 @@ class Tests_Comment_GetCommentLink extends WP_UnitTestCase {
 
 		$found = get_comment_link( self::$comments[5] );
 
-		$this->assertNotContains( 'cpage', $found );
+		$this->assertStringNotContainsString( 'cpage', $found );
 	}
 
 	/**
@@ -117,7 +117,7 @@ class Tests_Comment_GetCommentLink extends WP_UnitTestCase {
 
 		$found = get_comment_link( self::$comments[3] );
 
-		$this->assertContains( 'cpage=2', $found );
+		$this->assertStringContainsString( 'cpage=2', $found );
 	}
 
 	/**
@@ -130,7 +130,7 @@ class Tests_Comment_GetCommentLink extends WP_UnitTestCase {
 
 		$found = get_comment_link( self::$comments[1] );
 
-		$this->assertContains( 'cpage=3', $found );
+		$this->assertStringContainsString( 'cpage=3', $found );
 	}
 
 	/**
@@ -142,6 +142,6 @@ class Tests_Comment_GetCommentLink extends WP_UnitTestCase {
 
 		$found = get_comment_link( self::$comments[1] );
 
-		$this->assertNotContains( 'comment-page-1', $found );
+		$this->assertStringNotContainsString( 'comment-page-1', $found );
 	}
 }
diff --git a/tests/phpunit/tests/comment/getCommentReplyLink.php b/tests/phpunit/tests/comment/getCommentReplyLink.php
index 73e288501c..76332a5742 100644
--- a/tests/phpunit/tests/comment/getCommentReplyLink.php
+++ b/tests/phpunit/tests/comment/getCommentReplyLink.php
@@ -64,7 +64,7 @@ class Tests_Comment_GetCommentReplyLink extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( $expected_url, $comment_reply_link );
+		$this->assertStringContainsString( $expected_url, $comment_reply_link );
 	}
 
 	/**
diff --git a/tests/phpunit/tests/comment/query.php b/tests/phpunit/tests/comment/query.php
index 9366164e70..4fc3cd22ed 100644
--- a/tests/phpunit/tests/comment/query.php
+++ b/tests/phpunit/tests/comment/query.php
@@ -2484,7 +2484,7 @@ class Tests_Comment_Query extends WP_UnitTestCase {
 				'search' => false,
 			)
 		);
-		$this->assertNotContains( 'comment_author LIKE', $q->request );
+		$this->assertStringNotContainsString( 'comment_author LIKE', $q->request );
 	}
 
 	/**
@@ -2497,7 +2497,7 @@ class Tests_Comment_Query extends WP_UnitTestCase {
 				'search' => null,
 			)
 		);
-		$this->assertNotContains( 'comment_author LIKE', $q->request );
+		$this->assertStringNotContainsString( 'comment_author LIKE', $q->request );
 	}
 
 	/**
@@ -2510,7 +2510,7 @@ class Tests_Comment_Query extends WP_UnitTestCase {
 				'search' => false,
 			)
 		);
-		$this->assertNotContains( 'comment_author LIKE', $q->request );
+		$this->assertStringNotContainsString( 'comment_author LIKE', $q->request );
 	}
 
 	/**
@@ -2524,7 +2524,7 @@ class Tests_Comment_Query extends WP_UnitTestCase {
 				'search' => 0,
 			)
 		);
-		$this->assertContains( "comment_author LIKE '%0%'", $wpdb->remove_placeholder_escape( $q->request ) );
+		$this->assertStringContainsString( "comment_author LIKE '%0%'", $wpdb->remove_placeholder_escape( $q->request ) );
 	}
 
 	/**
@@ -2538,7 +2538,7 @@ class Tests_Comment_Query extends WP_UnitTestCase {
 				'search' => '0',
 			)
 		);
-		$this->assertContains( "comment_author LIKE '%0%'", $wpdb->remove_placeholder_escape( $q->request ) );
+		$this->assertStringContainsString( "comment_author LIKE '%0%'", $wpdb->remove_placeholder_escape( $q->request ) );
 	}
 
 	public function test_orderby_default() {
@@ -2547,7 +2547,7 @@ class Tests_Comment_Query extends WP_UnitTestCase {
 		$q = new WP_Comment_Query();
 		$q->query( array() );
 
-		$this->assertContains( "ORDER BY $wpdb->comments.comment_date_gmt", $q->request );
+		$this->assertStringContainsString( "ORDER BY $wpdb->comments.comment_date_gmt", $q->request );
 	}
 
 	public function test_orderby_single() {
@@ -2560,7 +2560,7 @@ class Tests_Comment_Query extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( "ORDER BY $wpdb->comments.comment_agent", $q->request );
+		$this->assertStringContainsString( "ORDER BY $wpdb->comments.comment_agent", $q->request );
 	}
 
 	public function test_orderby_single_invalid() {
@@ -2573,7 +2573,7 @@ class Tests_Comment_Query extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( "ORDER BY $wpdb->comments.comment_date_gmt", $q->request );
+		$this->assertStringContainsString( "ORDER BY $wpdb->comments.comment_date_gmt", $q->request );
 	}
 
 	public function test_orderby_space_separated() {
@@ -2586,7 +2586,7 @@ class Tests_Comment_Query extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( "ORDER BY $wpdb->comments.comment_agent DESC, $wpdb->comments.comment_approved DESC", $q->request );
+		$this->assertStringContainsString( "ORDER BY $wpdb->comments.comment_agent DESC, $wpdb->comments.comment_approved DESC", $q->request );
 	}
 
 	public function test_orderby_comma_separated() {
@@ -2599,7 +2599,7 @@ class Tests_Comment_Query extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( "ORDER BY $wpdb->comments.comment_agent DESC, $wpdb->comments.comment_approved DESC", $q->request );
+		$this->assertStringContainsString( "ORDER BY $wpdb->comments.comment_agent DESC, $wpdb->comments.comment_approved DESC", $q->request );
 	}
 
 	public function test_orderby_flat_array() {
@@ -2612,7 +2612,7 @@ class Tests_Comment_Query extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( "ORDER BY $wpdb->comments.comment_agent DESC, $wpdb->comments.comment_approved DESC", $q->request );
+		$this->assertStringContainsString( "ORDER BY $wpdb->comments.comment_agent DESC, $wpdb->comments.comment_approved DESC", $q->request );
 	}
 
 	public function test_orderby_array_contains_invalid_item() {
@@ -2625,7 +2625,7 @@ class Tests_Comment_Query extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( "ORDER BY $wpdb->comments.comment_agent DESC, $wpdb->comments.comment_approved DESC", $q->request );
+		$this->assertStringContainsString( "ORDER BY $wpdb->comments.comment_agent DESC, $wpdb->comments.comment_approved DESC", $q->request );
 	}
 
 	public function test_orderby_array_contains_all_invalid_items() {
@@ -2638,7 +2638,7 @@ class Tests_Comment_Query extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( "ORDER BY $wpdb->comments.comment_date_gmt", $q->request );
+		$this->assertStringContainsString( "ORDER BY $wpdb->comments.comment_date_gmt", $q->request );
 	}
 
 	/**
@@ -2652,7 +2652,7 @@ class Tests_Comment_Query extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertNotContains( 'ORDER BY', $q->request );
+		$this->assertStringNotContainsString( 'ORDER BY', $q->request );
 	}
 
 	/**
@@ -2666,7 +2666,7 @@ class Tests_Comment_Query extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertNotContains( 'ORDER BY', $q->request );
+		$this->assertStringNotContainsString( 'ORDER BY', $q->request );
 	}
 
 	/**
@@ -2680,7 +2680,7 @@ class Tests_Comment_Query extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertNotContains( 'ORDER BY', $q->request );
+		$this->assertStringNotContainsString( 'ORDER BY', $q->request );
 	}
 
 	/**
@@ -2701,7 +2701,7 @@ class Tests_Comment_Query extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( "ORDER BY $wpdb->comments.comment_agent DESC, $wpdb->comments.comment_date_gmt ASC, $wpdb->comments.comment_ID DESC", $q->request );
+		$this->assertStringContainsString( "ORDER BY $wpdb->comments.comment_agent DESC, $wpdb->comments.comment_date_gmt ASC, $wpdb->comments.comment_ID DESC", $q->request );
 	}
 
 	/**
@@ -2722,7 +2722,7 @@ class Tests_Comment_Query extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( "ORDER BY $wpdb->comments.comment_agent DESC, $wpdb->comments.comment_ID DESC", $q->request );
+		$this->assertStringContainsString( "ORDER BY $wpdb->comments.comment_agent DESC, $wpdb->comments.comment_ID DESC", $q->request );
 	}
 
 	/**
@@ -2743,7 +2743,7 @@ class Tests_Comment_Query extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( "ORDER BY $wpdb->comments.comment_agent DESC, $wpdb->comments.comment_date_gmt DESC, $wpdb->comments.comment_ID DESC", $q->request );
+		$this->assertStringContainsString( "ORDER BY $wpdb->comments.comment_agent DESC, $wpdb->comments.comment_date_gmt DESC, $wpdb->comments.comment_ID DESC", $q->request );
 	}
 
 	/**
@@ -2763,7 +2763,7 @@ class Tests_Comment_Query extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( "ORDER BY $wpdb->comments.comment_agent DESC, $wpdb->comments.comment_date_gmt ASC, $wpdb->comments.comment_ID ASC", $q->request );
+		$this->assertStringContainsString( "ORDER BY $wpdb->comments.comment_agent DESC, $wpdb->comments.comment_date_gmt ASC, $wpdb->comments.comment_ID ASC", $q->request );
 	}
 
 	/**
@@ -2783,7 +2783,7 @@ class Tests_Comment_Query extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( "ORDER BY $wpdb->comments.comment_agent DESC, $wpdb->comments.comment_date ASC, $wpdb->comments.comment_ID ASC", $q->request );
+		$this->assertStringContainsString( "ORDER BY $wpdb->comments.comment_agent DESC, $wpdb->comments.comment_date ASC, $wpdb->comments.comment_ID ASC", $q->request );
 	}
 
 	/**
@@ -2802,7 +2802,7 @@ class Tests_Comment_Query extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( "ORDER BY $wpdb->comments.comment_agent ASC, $wpdb->comments.comment_ID DESC", $q->request );
+		$this->assertStringContainsString( "ORDER BY $wpdb->comments.comment_agent ASC, $wpdb->comments.comment_ID DESC", $q->request );
 	}
 
 	/**
diff --git a/tests/phpunit/tests/customize/control.php b/tests/phpunit/tests/customize/control.php
index 950ef810a2..898fc7711f 100644
--- a/tests/phpunit/tests/customize/control.php
+++ b/tests/phpunit/tests/customize/control.php
@@ -118,14 +118,14 @@ class Test_WP_Customize_Control extends WP_UnitTestCase {
 		ob_start();
 		$page_on_front_control->maybe_render();
 		$content = ob_get_clean();
-		$this->assertNotContains( 'add-new-toggle', $content );
+		$this->assertStringNotContainsString( 'add-new-toggle', $content );
 
 		// Ensure the add-new-toggle is absent if allow_addition param is set.
 		$page_on_front_control->allow_addition = true;
 		ob_start();
 		$page_on_front_control->maybe_render();
 		$content = ob_get_clean();
-		$this->assertContains( 'add-new-toggle', $content );
+		$this->assertStringContainsString( 'add-new-toggle', $content );
 
 		// Ensure that dropdown-pages delect is rendered even if there are no pages published (yet).
 		foreach ( get_pages() as $page ) {
@@ -135,7 +135,7 @@ class Test_WP_Customize_Control extends WP_UnitTestCase {
 		ob_start();
 		$page_on_front_control->maybe_render();
 		$content = ob_get_clean();
-		$this->assertContains( '<option value="0">', $content, 'Dropdown-pages renders select even without any pages published.' );
+		$this->assertStringContainsString( '<option value="0">', $content, 'Dropdown-pages renders select even without any pages published.' );
 
 		// Ensure that auto-draft pages are included if they are among the nav_menus_created_posts.
 		$auto_draft_page_id = $this->factory()->post->create(
@@ -164,9 +164,9 @@ class Test_WP_Customize_Control extends WP_UnitTestCase {
 		ob_start();
 		$page_on_front_control->maybe_render();
 		$content = ob_get_clean();
-		$this->assertContains( sprintf( '<option value="%d">Auto Draft Page</option>', $auto_draft_page_id ), $content );
-		$this->assertNotContains( 'Auto Draft Post', $content );
-		$this->assertNotContains( 'Orphan Auto Draft Page', $content );
+		$this->assertStringContainsString( sprintf( '<option value="%d">Auto Draft Page</option>', $auto_draft_page_id ), $content );
+		$this->assertStringNotContainsString( 'Auto Draft Post', $content );
+		$this->assertStringNotContainsString( 'Orphan Auto Draft Page', $content );
 	}
 
 	/**
diff --git a/tests/phpunit/tests/customize/custom-css-setting.php b/tests/phpunit/tests/customize/custom-css-setting.php
index c1d9df7cd6..b82ea00fa2 100644
--- a/tests/phpunit/tests/customize/custom-css-setting.php
+++ b/tests/phpunit/tests/customize/custom-css-setting.php
@@ -331,9 +331,9 @@ class Test_WP_Customize_Custom_CSS_Setting extends WP_UnitTestCase {
 
 		$post = get_post( $post_id );
 		$this->assertSame( $original_title, $post->post_title );
-		$this->assertContains( $overridden_css, $post->post_content );
-		$this->assertContains( '/* filtered post_content */', $post->post_content );
-		$this->assertContains( '/* filtered post_content_filtered */', $post->post_content_filtered );
+		$this->assertStringContainsString( $overridden_css, $post->post_content );
+		$this->assertStringContainsString( '/* filtered post_content */', $post->post_content );
+		$this->assertStringContainsString( '/* filtered post_content_filtered */', $post->post_content_filtered );
 	}
 
 	/**
diff --git a/tests/phpunit/tests/customize/manager.php b/tests/phpunit/tests/customize/manager.php
index 430ad49b69..bdf7cb8059 100644
--- a/tests/phpunit/tests/customize/manager.php
+++ b/tests/phpunit/tests/customize/manager.php
@@ -242,7 +242,7 @@ class Tests_WP_Customize_Manager extends WP_UnitTestCase {
 			$exception = $e;
 		}
 		$this->assertInstanceOf( 'WPDieException', $exception );
-		$this->assertContains( 'you are not allowed to customize this site', $exception->getMessage() );
+		$this->assertStringContainsString( 'you are not allowed to customize this site', $exception->getMessage() );
 
 		// Bad changeset.
 		$exception = null;
@@ -254,7 +254,7 @@ class Tests_WP_Customize_Manager extends WP_UnitTestCase {
 			$exception = $e;
 		}
 		$this->assertInstanceOf( 'WPDieException', $exception );
-		$this->assertContains( 'Invalid changeset UUID', $exception->getMessage() );
+		$this->assertStringContainsString( 'Invalid changeset UUID', $exception->getMessage() );
 
 		update_option( 'fresh_site', '0' );
 		$wp_customize = new WP_Customize_Manager();
@@ -311,7 +311,7 @@ class Tests_WP_Customize_Manager extends WP_UnitTestCase {
 			$exception = $e;
 		}
 		$this->assertInstanceOf( 'WPDieException', $exception );
-		$this->assertContains( 'Non-existent changeset UUID', $exception->getMessage() );
+		$this->assertStringContainsString( 'Non-existent changeset UUID', $exception->getMessage() );
 
 		wp_set_current_user( self::$admin_user_id );
 		$wp_customize = new WP_Customize_Manager( array( 'messenger_channel' => 'preview-1' ) );
@@ -717,7 +717,7 @@ class Tests_WP_Customize_Manager extends WP_UnitTestCase {
 		$this->assertSame( 'Waffles', get_post( $posts_by_name['waffles'] )->post_title );
 		$this->assertSame( 'waffles', get_post_meta( $posts_by_name['waffles'], '_customize_draft_post_name', true ) );
 		$this->assertArrayHasKey( 'file', $attachment_metadata );
-		$this->assertContains( 'waffles', $attachment_metadata['file'] );
+		$this->assertStringContainsString( 'waffles', $attachment_metadata['file'] );
 
 		$this->assertSame( 'page', $changeset_values['show_on_front'] );
 		$this->assertSame( $posts_by_name['home'], $changeset_values['page_on_front'] );
@@ -798,9 +798,9 @@ class Tests_WP_Customize_Manager extends WP_UnitTestCase {
 		$this->assertNotEmpty( get_custom_logo() );
 		$this->assertNotEmpty( get_header_image() );
 		$this->assertNotEmpty( get_background_image() );
-		$this->assertContains( 'canola', get_custom_logo() );
-		$this->assertContains( 'waffles', get_header_image() );
-		$this->assertContains( 'waffles', get_background_image() );
+		$this->assertStringContainsString( 'canola', get_custom_logo() );
+		$this->assertStringContainsString( 'waffles', get_header_image() );
+		$this->assertStringContainsString( 'waffles', get_background_image() );
 		$this->assertSame( 'waffles', get_post( $posts_by_name['waffles'] )->post_name );
 		$this->assertEmpty( get_post_meta( $posts_by_name['waffles'], '_customize_draft_post_name', true ) );
 	}
@@ -920,7 +920,7 @@ class Tests_WP_Customize_Manager extends WP_UnitTestCase {
 			$exception = $e;
 		}
 		$this->assertNotNull( $exception );
-		$this->assertContains( 'Unauthorized', $exception->getMessage() );
+		$this->assertStringContainsString( 'Unauthorized', $exception->getMessage() );
 	}
 
 	/**
@@ -1210,7 +1210,7 @@ class Tests_WP_Customize_Manager extends WP_UnitTestCase {
 		$this->assertSame( 'Do it live \o/', get_option( 'blogname' ) );
 		$this->assertSame( 'trash', get_post_status( $post_id ) ); // Auto-trashed.
 		$this->assertSame( $original_capabilities, wp_list_pluck( $manager->settings(), 'capability' ) );
-		$this->assertContains( '<script>', get_post( $post_id )->post_content );
+		$this->assertStringContainsString( '<script>', get_post( $post_id )->post_content );
 		$this->assertSame( $manager->changeset_uuid(), get_post( $post_id )->post_name, 'Expected that the "__trashed" suffix to not be added.' );
 		wp_set_current_user( self::$admin_user_id );
 		$this->assertSame( 'publish', get_post_meta( $post_id, '_wp_trash_meta_status', true ) );
@@ -1339,16 +1339,16 @@ class Tests_WP_Customize_Manager extends WP_UnitTestCase {
 		);
 
 		// User saved as one who can bypass content_save_pre filter.
-		$this->assertContains( '<script>', get_option( 'custom_html_1' ) );
-		$this->assertContains( 'Wordpress', get_option( 'custom_html_1' ) ); // phpcs:ignore WordPress.WP.CapitalPDangit.Misspelled
+		$this->assertStringContainsString( '<script>', get_option( 'custom_html_1' ) );
+		$this->assertStringContainsString( 'Wordpress', get_option( 'custom_html_1' ) ); // phpcs:ignore WordPress.WP.CapitalPDangit.Misspelled
 
 		// User saved as one who cannot bypass content_save_pre filter.
-		$this->assertNotContains( '<script>', get_option( 'custom_html_2' ) );
-		$this->assertContains( 'WordPress', get_option( 'custom_html_2' ) );
+		$this->assertStringNotContainsString( '<script>', get_option( 'custom_html_2' ) );
+		$this->assertStringContainsString( 'WordPress', get_option( 'custom_html_2' ) );
 
 		// User saved as one who also cannot bypass content_save_pre filter.
-		$this->assertNotContains( '<script>', get_option( 'custom_html_3' ) );
-		$this->assertContains( 'WordPress', get_option( 'custom_html_3' ) );
+		$this->assertStringNotContainsString( '<script>', get_option( 'custom_html_3' ) );
+		$this->assertStringContainsString( 'WordPress', get_option( 'custom_html_3' ) );
 	}
 
 	/**
@@ -1833,7 +1833,7 @@ class Tests_WP_Customize_Manager extends WP_UnitTestCase {
 			)
 		);
 		$this->assertFalse( wp_get_post_autosave( $changeset_post_id, get_current_user_id() ) );
-		$this->assertContains( 'Autosaved Auto-draft Title', get_post( $changeset_post_id )->post_content );
+		$this->assertStringContainsString( 'Autosaved Auto-draft Title', get_post( $changeset_post_id )->post_content );
 
 		// Update status to draft for subsequent tests.
 		$wp_customize->save_changeset_post(
@@ -1847,7 +1847,7 @@ class Tests_WP_Customize_Manager extends WP_UnitTestCase {
 				'autosave' => false,
 			)
 		);
-		$this->assertContains( 'Draft Title', get_post( $changeset_post_id )->post_content );
+		$this->assertStringContainsString( 'Draft Title', get_post( $changeset_post_id )->post_content );
 
 		// Fail: illegal_autosave_with_date_gmt.
 		$r = $wp_customize->save_changeset_post(
@@ -1894,8 +1894,8 @@ class Tests_WP_Customize_Manager extends WP_UnitTestCase {
 		// Verify that autosave happened.
 		$autosave_revision = wp_get_post_autosave( $changeset_post_id, get_current_user_id() );
 		$this->assertInstanceOf( 'WP_Post', $autosave_revision );
-		$this->assertContains( 'Draft Title', get_post( $changeset_post_id )->post_content );
-		$this->assertContains( 'Autosave Title', $autosave_revision->post_content );
+		$this->assertStringContainsString( 'Draft Title', get_post( $changeset_post_id )->post_content );
+		$this->assertStringContainsString( 'Autosave Title', $autosave_revision->post_content );
 	}
 
 	/**
@@ -2940,7 +2940,7 @@ class Tests_WP_Customize_Manager extends WP_UnitTestCase {
 	 */
 	function test_get_document_title_template() {
 		$tpl = $this->manager->get_document_title_template();
-		$this->assertContains( '%s', $tpl );
+		$this->assertStringContainsString( '%s', $tpl );
 	}
 
 	/**
@@ -3079,12 +3079,12 @@ class Tests_WP_Customize_Manager extends WP_UnitTestCase {
 		$this->manager->customize_pane_settings();
 		$content = ob_get_clean();
 
-		$this->assertContains( 'var _wpCustomizeSettings =', $content );
-		$this->assertContains( '"blogname"', $content );
-		$this->assertContains( '"type":"option"', $content );
-		$this->assertContains( '_wpCustomizeSettings.controls', $content );
-		$this->assertContains( '_wpCustomizeSettings.settings', $content );
-		$this->assertContains( '</script>', $content );
+		$this->assertStringContainsString( 'var _wpCustomizeSettings =', $content );
+		$this->assertStringContainsString( '"blogname"', $content );
+		$this->assertStringContainsString( '"type":"option"', $content );
+		$this->assertStringContainsString( '_wpCustomizeSettings.controls', $content );
+		$this->assertStringContainsString( '_wpCustomizeSettings.settings', $content );
+		$this->assertStringContainsString( '</script>', $content );
 
 		$this->assertNotEmpty( preg_match( '#var _wpCustomizeSettings\s*=\s*({.*?});\s*\n#', $content, $matches ) );
 		$json = $matches[1];
@@ -3131,7 +3131,7 @@ class Tests_WP_Customize_Manager extends WP_UnitTestCase {
 		ob_start();
 		$manager->remove_frameless_preview_messenger_channel();
 		$output = ob_get_clean();
-		$this->assertContains( '<script>', $output );
+		$this->assertStringContainsString( '<script>', $output );
 	}
 
 	/**
diff --git a/tests/phpunit/tests/customize/nav-menus.php b/tests/phpunit/tests/customize/nav-menus.php
index 908a7ad4f7..b1c604beff 100644
--- a/tests/phpunit/tests/customize/nav-menus.php
+++ b/tests/phpunit/tests/customize/nav-menus.php
@@ -745,7 +745,7 @@ class Test_WP_Customize_Nav_Menus extends WP_UnitTestCase {
 			esc_html( 'Move one level down' )
 		);
 
-		$this->assertContains( $expected, $template );
+		$this->assertStringContainsString( $expected, $template );
 	}
 
 	/**
@@ -764,35 +764,35 @@ class Test_WP_Customize_Nav_Menus extends WP_UnitTestCase {
 
 		$expected = sprintf( 'Customizing &#9656; %s', esc_html( $this->wp_customize->get_panel( 'nav_menus' )->title ) );
 
-		$this->assertContains( $expected, $template );
+		$this->assertStringContainsString( $expected, $template );
 
 		$post_types = get_post_types( array( 'show_in_nav_menus' => true ), 'object' );
 		if ( $post_types ) {
 			foreach ( $post_types as $type ) {
-				$this->assertContains( 'available-menu-items-post_type-' . esc_attr( $type->name ), $template );
+				$this->assertStringContainsString( 'available-menu-items-post_type-' . esc_attr( $type->name ), $template );
 				$this->assertRegExp( '#<h4 class="accordion-section-title".*>\s*' . esc_html( $type->labels->name ) . '#', $template );
-				$this->assertContains( 'data-type="post_type"', $template );
-				$this->assertContains( 'data-object="' . esc_attr( $type->name ) . '"', $template );
-				$this->assertContains( 'data-type_label="' . esc_attr( $type->labels->singular_name ) . '"', $template );
+				$this->assertStringContainsString( 'data-type="post_type"', $template );
+				$this->assertStringContainsString( 'data-object="' . esc_attr( $type->name ) . '"', $template );
+				$this->assertStringContainsString( 'data-type_label="' . esc_attr( $type->labels->singular_name ) . '"', $template );
 			}
 		}
 
 		$taxonomies = get_taxonomies( array( 'show_in_nav_menus' => true ), 'object' );
 		if ( $taxonomies ) {
 			foreach ( $taxonomies as $tax ) {
-				$this->assertContains( 'available-menu-items-taxonomy-' . esc_attr( $tax->name ), $template );
+				$this->assertStringContainsString( 'available-menu-items-taxonomy-' . esc_attr( $tax->name ), $template );
 				$this->assertRegExp( '#<h4 class="accordion-section-title".*>\s*' . esc_html( $tax->labels->name ) . '#', $template );
-				$this->assertContains( 'data-type="taxonomy"', $template );
-				$this->assertContains( 'data-object="' . esc_attr( $tax->name ) . '"', $template );
-				$this->assertContains( 'data-type_label="' . esc_attr( $tax->labels->singular_name ) . '"', $template );
+				$this->assertStringContainsString( 'data-type="taxonomy"', $template );
+				$this->assertStringContainsString( 'data-object="' . esc_attr( $tax->name ) . '"', $template );
+				$this->assertStringContainsString( 'data-type_label="' . esc_attr( $tax->labels->singular_name ) . '"', $template );
 			}
 		}
 
-		$this->assertContains( 'available-menu-items-custom_type', $template );
+		$this->assertStringContainsString( 'available-menu-items-custom_type', $template );
 		$this->assertRegExp( '#<h4 class="accordion-section-title".*>\s*Custom#', $template );
-		$this->assertContains( 'data-type="custom_type"', $template );
-		$this->assertContains( 'data-object="custom_object"', $template );
-		$this->assertContains( 'data-type_label="Custom Type"', $template );
+		$this->assertStringContainsString( 'data-type="custom_type"', $template );
+		$this->assertStringContainsString( 'data-object="custom_object"', $template );
+		$this->assertStringContainsString( 'data-type_label="Custom Type"', $template );
 	}
 
 	/**
@@ -1140,8 +1140,8 @@ class Test_WP_Customize_Nav_Menus extends WP_UnitTestCase {
 
 		$result = $menus->filter_wp_nav_menu( $nav_menu_content, (object) $args );
 
-		$this->assertContains( sprintf( ' data-customize-partial-id="nav_menu_instance[%s]"', $args['customize_preview_nav_menus_args']['args_hmac'] ), $result );
-		$this->assertContains( ' data-customize-partial-type="nav_menu_instance"', $result );
+		$this->assertStringContainsString( sprintf( ' data-customize-partial-id="nav_menu_instance[%s]"', $args['customize_preview_nav_menus_args']['args_hmac'] ), $result );
+		$this->assertStringContainsString( ' data-customize-partial-type="nav_menu_instance"', $result );
 		$this->assertTrue( (bool) preg_match( '/data-customize-partial-placement-context="(.+?)"/', $result, $matches ) );
 		$context = json_decode( html_entity_decode( $matches[1] ), true );
 		$this->assertSame( $original_args, wp_array_slice_assoc( $context, array_keys( $original_args ) ) ); // Because assertArraySubset is not available in PHP 5.2.
@@ -1225,7 +1225,7 @@ class Test_WP_Customize_Nav_Menus extends WP_UnitTestCase {
 		$this->assertFalse( $partial->render( $args_hmac_mismatch_args ) );
 
 		$rendered = $partial->render( $nav_menu_args['customize_preview_nav_menus_args'] );
-		$this->assertContains( 'data-customize-partial-type="nav_menu_instance"', $rendered );
-		$this->assertContains( 'WordPress.org', $rendered );
+		$this->assertStringContainsString( 'data-customize-partial-type="nav_menu_instance"', $rendered );
+		$this->assertStringContainsString( 'WordPress.org', $rendered );
 	}
 }
diff --git a/tests/phpunit/tests/customize/panel.php b/tests/phpunit/tests/customize/panel.php
index 6a5f30b3e7..f3be0961a0 100644
--- a/tests/phpunit/tests/customize/panel.php
+++ b/tests/phpunit/tests/customize/panel.php
@@ -189,12 +189,12 @@ class Tests_WP_Customize_Panel extends WP_UnitTestCase {
 		ob_start();
 		$panel->print_template();
 		$content = ob_get_clean();
-		$this->assertContains( '<script type="text/html" id="tmpl-customize-panel-default-content">', $content );
-		$this->assertContains( 'accordion-section-title', $content );
-		$this->assertContains( 'control-panel-content', $content );
-		$this->assertContains( '<script type="text/html" id="tmpl-customize-panel-default">', $content );
-		$this->assertContains( 'customize-panel-description', $content );
-		$this->assertContains( 'preview-notice', $content );
+		$this->assertStringContainsString( '<script type="text/html" id="tmpl-customize-panel-default-content">', $content );
+		$this->assertStringContainsString( 'accordion-section-title', $content );
+		$this->assertStringContainsString( 'control-panel-content', $content );
+		$this->assertStringContainsString( '<script type="text/html" id="tmpl-customize-panel-default">', $content );
+		$this->assertStringContainsString( 'customize-panel-description', $content );
+		$this->assertStringContainsString( 'preview-notice', $content );
 	}
 
 	/**
@@ -207,11 +207,11 @@ class Tests_WP_Customize_Panel extends WP_UnitTestCase {
 		ob_start();
 		$panel->print_template();
 		$content = ob_get_clean();
-		$this->assertContains( '<script type="text/html" id="tmpl-customize-panel-titleless-content">', $content );
-		$this->assertNotContains( 'accordion-section-title', $content );
+		$this->assertStringContainsString( '<script type="text/html" id="tmpl-customize-panel-titleless-content">', $content );
+		$this->assertStringNotContainsString( 'accordion-section-title', $content );
 
-		$this->assertContains( '<script type="text/html" id="tmpl-customize-panel-titleless">', $content );
-		$this->assertNotContains( 'preview-notice', $content );
+		$this->assertStringContainsString( '<script type="text/html" id="tmpl-customize-panel-titleless">', $content );
+		$this->assertStringNotContainsString( 'preview-notice', $content );
 	}
 }
 
diff --git a/tests/phpunit/tests/customize/partial.php b/tests/phpunit/tests/customize/partial.php
index 8d2723c1ab..e297f0cc73 100644
--- a/tests/phpunit/tests/customize/partial.php
+++ b/tests/phpunit/tests/customize/partial.php
@@ -111,7 +111,7 @@ class Test_WP_Customize_Partial extends WP_UnitTestCase {
 		$this->assertSame( $args['render_callback'], $partial->render_callback );
 		$this->assertFalse( $partial->container_inclusive );
 		$this->assertFalse( $partial->fallback_refresh );
-		$this->assertContains( 'Lorem Ipsum', $partial->render() );
+		$this->assertStringContainsString( 'Lorem Ipsum', $partial->render() );
 
 		$partial = new WP_Customize_Partial(
 			$this->selective_refresh,
diff --git a/tests/phpunit/tests/customize/section.php b/tests/phpunit/tests/customize/section.php
index d55649d71e..970ef2111c 100644
--- a/tests/phpunit/tests/customize/section.php
+++ b/tests/phpunit/tests/customize/section.php
@@ -202,9 +202,9 @@ class Tests_WP_Customize_Section extends WP_UnitTestCase {
 		ob_start();
 		$section->print_template();
 		$content = ob_get_clean();
-		$this->assertContains( '<script type="text/html" id="tmpl-customize-section-default">', $content );
-		$this->assertContains( 'accordion-section-title', $content );
-		$this->assertContains( 'accordion-section-content', $content );
+		$this->assertStringContainsString( '<script type="text/html" id="tmpl-customize-section-default">', $content );
+		$this->assertStringContainsString( 'accordion-section-title', $content );
+		$this->assertStringContainsString( 'accordion-section-content', $content );
 	}
 
 	/**
@@ -217,9 +217,9 @@ class Tests_WP_Customize_Section extends WP_UnitTestCase {
 		ob_start();
 		$section->print_template();
 		$content = ob_get_clean();
-		$this->assertContains( '<script type="text/html" id="tmpl-customize-section-titleless">', $content );
-		$this->assertNotContains( 'accordion-section-title', $content );
-		$this->assertContains( 'accordion-section-content', $content );
+		$this->assertStringContainsString( '<script type="text/html" id="tmpl-customize-section-titleless">', $content );
+		$this->assertStringNotContainsString( 'accordion-section-title', $content );
+		$this->assertStringContainsString( 'accordion-section-content', $content );
 	}
 }
 
diff --git a/tests/phpunit/tests/customize/widgets.php b/tests/phpunit/tests/customize/widgets.php
index 595021d96b..5f183189ff 100644
--- a/tests/phpunit/tests/customize/widgets.php
+++ b/tests/phpunit/tests/customize/widgets.php
@@ -579,10 +579,10 @@ class Tests_WP_Customize_Widgets extends WP_UnitTestCase {
 		$this->do_customize_boot_actions();
 		$widget_control = $this->manager->widgets->get_widget_control( $this->get_test_widget_control_args() );
 
-		$this->assertContains( '<div class="form">', $widget_control );
-		$this->assertContains( '<div class="widget-content">', $widget_control );
-		$this->assertContains( '<input type="hidden" name="id_base" class="id_base" value="search"', $widget_control );
-		$this->assertContains( '<input class="widefat"', $widget_control );
+		$this->assertStringContainsString( '<div class="form">', $widget_control );
+		$this->assertStringContainsString( '<div class="widget-content">', $widget_control );
+		$this->assertStringContainsString( '<input type="hidden" name="id_base" class="id_base" value="search"', $widget_control );
+		$this->assertStringContainsString( '<input class="widefat"', $widget_control );
 	}
 
 	/**
@@ -594,11 +594,11 @@ class Tests_WP_Customize_Widgets extends WP_UnitTestCase {
 		$this->assertArrayHasKey( 'content', $widget_control_parts );
 		$this->assertArrayHasKey( 'control', $widget_control_parts );
 
-		$this->assertContains( '<div class="form">', $widget_control_parts['control'] );
-		$this->assertContains( '<div class="widget-content">', $widget_control_parts['control'] );
-		$this->assertContains( '<input type="hidden" name="id_base" class="id_base" value="search"', $widget_control_parts['control'] );
-		$this->assertNotContains( '<input class="widefat"', $widget_control_parts['control'] );
-		$this->assertContains( '<input class="widefat"', $widget_control_parts['content'] );
+		$this->assertStringContainsString( '<div class="form">', $widget_control_parts['control'] );
+		$this->assertStringContainsString( '<div class="widget-content">', $widget_control_parts['control'] );
+		$this->assertStringContainsString( '<input type="hidden" name="id_base" class="id_base" value="search"', $widget_control_parts['control'] );
+		$this->assertStringNotContainsString( '<input class="widefat"', $widget_control_parts['control'] );
+		$this->assertStringContainsString( '<input class="widefat"', $widget_control_parts['content'] );
 	}
 
 	/**
@@ -612,9 +612,9 @@ class Tests_WP_Customize_Widgets extends WP_UnitTestCase {
 		$this->assertSame( 'widget_form', $params['type'] );
 		$this->assertRegExp( '#^<li[^>]+>\s*</li>$#', $params['content'] );
 		$this->assertRegExp( '#^<div[^>]*class=\'widget\'[^>]*#s', $params['widget_control'] );
-		$this->assertContains( '<div class="widget-content"></div>', $params['widget_control'] );
-		$this->assertNotContains( '<input class="widefat"', $params['widget_control'] );
-		$this->assertContains( '<input class="widefat"', $params['widget_content'] );
+		$this->assertStringContainsString( '<div class="widget-content"></div>', $params['widget_control'] );
+		$this->assertStringNotContainsString( '<input class="widefat"', $params['widget_control'] );
+		$this->assertStringContainsString( '<input class="widefat"', $params['widget_content'] );
 		$this->assertSame( 'search-2', $params['widget_id'] );
 		$this->assertSame( 'search', $params['widget_id_base'] );
 		$this->assertArrayHasKey( 'sidebar_id', $params );
@@ -681,7 +681,7 @@ class Tests_WP_Customize_Widgets extends WP_UnitTestCase {
 		$this->assertArrayHasKey( 'instance', $result );
 		$this->assertArrayHasKey( 'form', $result );
 		$this->assertSame( $instance, $result['instance'] );
-		$this->assertContains( sprintf( 'value="%s"', esc_attr( $instance['title'] ) ), $result['form'] );
+		$this->assertStringContainsString( sprintf( 'value="%s"', esc_attr( $instance['title'] ) ), $result['form'] );
 
 		$post_values = $this->manager->unsanitized_post_values();
 		$this->assertArrayHasKey( $setting_id, $post_values );
@@ -814,8 +814,8 @@ class Tests_WP_Customize_Widgets extends WP_UnitTestCase {
 		$this->assertSame( '<!--dynamic_sidebar_after:foo:1-->', trim( $output ) );
 
 		$output = wp_kses_post( $filtered_params[0]['before_widget'] );
-		$this->assertContains( 'data-customize-partial-id="widget[search-2]"', $output );
-		$this->assertContains( 'data-customize-partial-type="widget"', $output );
+		$this->assertStringContainsString( 'data-customize-partial-id="widget[search-2]"', $output );
+		$this->assertStringContainsString( 'data-customize-partial-type="widget"', $output );
 	}
 
 	/**
@@ -841,7 +841,7 @@ class Tests_WP_Customize_Widgets extends WP_UnitTestCase {
 
 		$this->assertSame( 1, substr_count( $output, 'data-customize-partial-id' ) );
 		$this->assertSame( 1, substr_count( $output, 'data-customize-partial-type="widget"' ) );
-		$this->assertContains( ' id="search-2"', $output );
+		$this->assertStringContainsString( ' id="search-2"', $output );
 	}
 
 	/**
diff --git a/tests/phpunit/tests/date/query.php b/tests/phpunit/tests/date/query.php
index 87cb8b7632..a0d84cbc35 100644
--- a/tests/phpunit/tests/date/query.php
+++ b/tests/phpunit/tests/date/query.php
@@ -610,7 +610,7 @@ class Tests_Date_Query extends WP_UnitTestCase {
 
 		$found = $q->build_time_query( 'post_date', '=', 0, 10 );
 
-		$this->assertContains( '%H', $wpdb->remove_placeholder_escape( $found ) );
+		$this->assertStringContainsString( '%H', $wpdb->remove_placeholder_escape( $found ) );
 	}
 
 	public function test_build_time_query_compare_in() {
diff --git a/tests/phpunit/tests/db.php b/tests/phpunit/tests/db.php
index 0ebc357666..c7968cd4d4 100644
--- a/tests/phpunit/tests/db.php
+++ b/tests/phpunit/tests/db.php
@@ -99,11 +99,11 @@ class Tests_DB extends WP_UnitTestCase {
 		$wpdb->suppress_errors( false );
 
 		// Ensure the float isn't 0,700.
-		$this->assertContains( '0.700', array_pop( $this->_queries ) );
+		$this->assertStringContainsString( '0.700', array_pop( $this->_queries ) );
 
 		// Try a prepare.
 		$sql = $wpdb->prepare( 'UPDATE test_table SET float_column = %f AND meta_id = %d', 0.7, 5 );
-		$this->assertContains( '0.700', $sql );
+		$this->assertStringContainsString( '0.700', $sql );
 
 		// Restore locale settings.
 		foreach ( $current_locales as $locale_setting ) {
@@ -270,7 +270,7 @@ class Tests_DB extends WP_UnitTestCase {
 	public function test_double_escaped_placeholders() {
 		global $wpdb;
 		$sql = $wpdb->prepare( "UPDATE test_table SET string_column = '%%f is a float, %%d is an int %d, %%s is a string', field = %s", 3, '4' );
-		$this->assertContains( $wpdb->placeholder_escape(), $sql );
+		$this->assertStringContainsString( $wpdb->placeholder_escape(), $sql );
 
 		$sql = $wpdb->remove_placeholder_escape( $sql );
 		$this->assertSame( "UPDATE test_table SET string_column = '%f is a float, %d is an int 3, %s is a string', field = '4'", $sql );
@@ -1608,7 +1608,7 @@ class Tests_DB extends WP_UnitTestCase {
 		global $wpdb;
 
 		$part = $wpdb->prepare( ' AND meta_value = %s', ' %s ' );
-		$this->assertNotContains( '%s', $part );
+		$this->assertStringNotContainsString( '%s', $part );
 		// phpcs:ignore WordPress.DB.PreparedSQLPlaceholders.ReplacementsWrongNumber
 		$query = $wpdb->prepare( 'SELECT * FROM {$wpdb->postmeta} WHERE meta_key = %s $part', array( 'foo', 'bar' ) );
 		$this->assertNull( $query );
@@ -1625,8 +1625,8 @@ class Tests_DB extends WP_UnitTestCase {
 		);
 
 		/* Floats can be right padded, need to assert differently */
-		$this->assertContains( ' first=1.1', $actual );
-		$this->assertContains( ' second=2.2', $actual );
+		$this->assertStringContainsString( ' first=1.1', $actual );
+		$this->assertStringContainsString( ' second=2.2', $actual );
 	}
 
 	function test_prepare_numeric_placeholders_float_array() {
@@ -1639,8 +1639,8 @@ class Tests_DB extends WP_UnitTestCase {
 		);
 
 		/* Floats can be right padded, need to assert differently */
-		$this->assertContains( ' first=1.1', $actual );
-		$this->assertContains( ' second=2.2', $actual );
+		$this->assertStringContainsString( ' first=1.1', $actual );
+		$this->assertStringContainsString( ' second=2.2', $actual );
 	}
 
 	function test_query_unescapes_placeholders() {
@@ -1658,7 +1658,7 @@ class Tests_DB extends WP_UnitTestCase {
 
 		$wpdb->query( "DROP TABLE {$wpdb->prefix}test_placeholder" );
 
-		$this->assertNotContains( '%s', $sql );
+		$this->assertStringNotContainsString( '%s', $sql );
 		$this->assertSame( $value, $actual );
 	}
 
diff --git a/tests/phpunit/tests/dependencies/scripts.php b/tests/phpunit/tests/dependencies/scripts.php
index ddcf04a85f..75d8ea0416 100644
--- a/tests/phpunit/tests/dependencies/scripts.php
+++ b/tests/phpunit/tests/dependencies/scripts.php
@@ -262,8 +262,8 @@ JS;
 		$footer = get_echo( 'wp_print_footer_scripts' );
 
 		$this->assertEmpty( $header );
-		$this->assertContains( home_url( 'bar.js' ), $footer );
-		$this->assertContains( home_url( 'baz.js' ), $footer );
+		$this->assertStringContainsString( home_url( 'bar.js' ), $footer );
+		$this->assertStringContainsString( home_url( 'baz.js' ), $footer );
 	}
 
 	/**
diff --git a/tests/phpunit/tests/dependencies/styles.php b/tests/phpunit/tests/dependencies/styles.php
index 444430719a..754c15cc85 100644
--- a/tests/phpunit/tests/dependencies/styles.php
+++ b/tests/phpunit/tests/dependencies/styles.php
@@ -318,7 +318,7 @@ CSS;
 	 */
 	function test_wp_enqueue_style_with_media( $expected, $media ) {
 		wp_enqueue_style( 'handle', 'http://example.com', array(), 1, $media );
-		$this->assertContains( $expected, get_echo( 'wp_print_styles' ) );
+		$this->assertStringContainsString( $expected, get_echo( 'wp_print_styles' ) );
 	}
 
 	function data_styles_with_media() {
diff --git a/tests/phpunit/tests/feed/rss2.php b/tests/phpunit/tests/feed/rss2.php
index 25c0efcc45..34aa3b29e0 100644
--- a/tests/phpunit/tests/feed/rss2.php
+++ b/tests/phpunit/tests/feed/rss2.php
@@ -172,7 +172,7 @@ class Tests_Feeds_RSS2 extends WP_UnitTestCase {
 
 		// Verify the date is untranslated.
 		$pubdate = xml_find( $xml, 'rss', 'channel', 'lastBuildDate' );
-		$this->assertNotContains( 'Tue_Translated', $pubdate[0]['content'] );
+		$this->assertStringNotContainsString( 'Tue_Translated', $pubdate[0]['content'] );
 	}
 
 	function test_item_elements() {
diff --git a/tests/phpunit/tests/formatting/Emoji.php b/tests/phpunit/tests/formatting/Emoji.php
index 0c79d3174e..85951a0726 100644
--- a/tests/phpunit/tests/formatting/Emoji.php
+++ b/tests/phpunit/tests/formatting/Emoji.php
@@ -17,8 +17,8 @@ class Tests_Formatting_Emoji extends WP_UnitTestCase {
 		self::touch( ABSPATH . WPINC . '/js/wp-emoji-loader.js' );
 		$output = get_echo( '_print_emoji_detection_script' );
 
-		$this->assertContains( wp_json_encode( $this->png_cdn ), $output );
-		$this->assertContains( wp_json_encode( $this->svn_cdn ), $output );
+		$this->assertStringContainsString( wp_json_encode( $this->png_cdn ), $output );
+		$this->assertStringContainsString( wp_json_encode( $this->svn_cdn ), $output );
 	}
 
 	public function _filtered_emoji_svn_cdn( $cdn = '' ) {
@@ -37,9 +37,9 @@ class Tests_Formatting_Emoji extends WP_UnitTestCase {
 		self::touch( ABSPATH . WPINC . '/js/wp-emoji-loader.js' );
 		$output = get_echo( '_print_emoji_detection_script' );
 
-		$this->assertContains( wp_json_encode( $this->png_cdn ), $output );
-		$this->assertNotContains( wp_json_encode( $this->svn_cdn ), $output );
-		$this->assertContains( wp_json_encode( $filtered_svn_cdn ), $output );
+		$this->assertStringContainsString( wp_json_encode( $this->png_cdn ), $output );
+		$this->assertStringNotContainsString( wp_json_encode( $this->svn_cdn ), $output );
+		$this->assertStringContainsString( wp_json_encode( $filtered_svn_cdn ), $output );
 
 		remove_filter( 'emoji_svg_url', array( $this, '_filtered_emoji_svn_cdn' ) );
 	}
@@ -60,9 +60,9 @@ class Tests_Formatting_Emoji extends WP_UnitTestCase {
 		self::touch( ABSPATH . WPINC . '/js/wp-emoji-loader.js' );
 		$output = get_echo( '_print_emoji_detection_script' );
 
-		$this->assertContains( wp_json_encode( $filtered_png_cdn ), $output );
-		$this->assertNotContains( wp_json_encode( $this->png_cdn ), $output );
-		$this->assertContains( wp_json_encode( $this->svn_cdn ), $output );
+		$this->assertStringContainsString( wp_json_encode( $filtered_png_cdn ), $output );
+		$this->assertStringNotContainsString( wp_json_encode( $this->png_cdn ), $output );
+		$this->assertStringContainsString( wp_json_encode( $this->svn_cdn ), $output );
 
 		remove_filter( 'emoji_url', array( $this, '_filtered_emoji_png_cdn' ) );
 	}
diff --git a/tests/phpunit/tests/formatting/MakeClickable.php b/tests/phpunit/tests/formatting/MakeClickable.php
index 612d7a1350..8841548fa6 100644
--- a/tests/phpunit/tests/formatting/MakeClickable.php
+++ b/tests/phpunit/tests/formatting/MakeClickable.php
@@ -432,7 +432,7 @@ class Tests_Formatting_MakeClickable extends WP_UnitTestCase {
 		comment_text( $comment_id );
 		$comment_text = ob_get_clean();
 
-		$this->assertContains( $expected, make_clickable( $comment_text ) );
+		$this->assertStringContainsString( $expected, make_clickable( $comment_text ) );
 	}
 
 	public function data_add_rel_ugc_in_comments() {
diff --git a/tests/phpunit/tests/general/paginateLinks.php b/tests/phpunit/tests/general/paginateLinks.php
index 9d4fd4a14d..3d992e3998 100644
--- a/tests/phpunit/tests/general/paginateLinks.php
+++ b/tests/phpunit/tests/general/paginateLinks.php
@@ -311,10 +311,10 @@ EXPECTED;
 			)
 		);
 
-		$this->assertContains( '?foo=1', $links[1] );
-		$this->assertContains( '?foo=2', $links[2] );
-		$this->assertContains( '?foo=4', $links[4] );
-		$this->assertContains( '?foo=5', $links[5] );
+		$this->assertStringContainsString( '?foo=1', $links[1] );
+		$this->assertStringContainsString( '?foo=2', $links[2] );
+		$this->assertStringContainsString( '?foo=4', $links[4] );
+		$this->assertStringContainsString( '?foo=5', $links[5] );
 
 		$_SERVER['REQUEST_URI'] = $request_uri;
 	}
diff --git a/tests/phpunit/tests/general/wpResourceHints.php b/tests/phpunit/tests/general/wpResourceHints.php
index 4919945052..da8d358864 100644
--- a/tests/phpunit/tests/general/wpResourceHints.php
+++ b/tests/phpunit/tests/general/wpResourceHints.php
@@ -195,7 +195,7 @@ class Tests_General_wpResourceHints extends WP_UnitTestCase {
 		wp_deregister_script( 'jquery-elsewhere' );
 
 		$this->assertSame( $expected, $actual );
-		$this->assertNotContains( $unexpected, $actual );
+		$this->assertStringNotContainsString( $unexpected, $actual );
 	}
 
 	/**
diff --git a/tests/phpunit/tests/l10n.php b/tests/phpunit/tests/l10n.php
index b4bbb07725..87c0f6fa79 100644
--- a/tests/phpunit/tests/l10n.php
+++ b/tests/phpunit/tests/l10n.php
@@ -101,12 +101,12 @@ class Tests_L10n extends WP_UnitTestCase {
 		);
 		$actual = wp_dropdown_languages( $args );
 
-		$this->assertContains( 'id="foo"', $actual );
-		$this->assertContains( 'name="bar"', $actual );
-		$this->assertContains( '<option value="" lang="en" data-installed="1">English (United States)</option>', $actual );
-		$this->assertContains( '<option value="de_DE" lang="de" selected=\'selected\' data-installed="1">Deutsch</option>', $actual );
-		$this->assertContains( '<option value="it_IT" lang="it">Italiano</option>', $actual );
-		$this->assertContains( '<option value="ja_JP" lang="ja">日本語</option>', $actual );
+		$this->assertStringContainsString( 'id="foo"', $actual );
+		$this->assertStringContainsString( 'name="bar"', $actual );
+		$this->assertStringContainsString( '<option value="" lang="en" data-installed="1">English (United States)</option>', $actual );
+		$this->assertStringContainsString( '<option value="de_DE" lang="de" selected=\'selected\' data-installed="1">Deutsch</option>', $actual );
+		$this->assertStringContainsString( '<option value="it_IT" lang="it">Italiano</option>', $actual );
+		$this->assertStringContainsString( '<option value="ja_JP" lang="ja">日本語</option>', $actual );
 	}
 
 	/**
@@ -124,13 +124,13 @@ class Tests_L10n extends WP_UnitTestCase {
 		);
 		$actual = wp_dropdown_languages( $args );
 
-		$this->assertContains( 'id="foo"', $actual );
-		$this->assertContains( 'name="bar"', $actual );
-		$this->assertContains( '<option value="site-default" data-installed="1">Site Default</option>', $actual );
-		$this->assertContains( '<option value="" lang="en" data-installed="1">English (United States)</option>', $actual );
-		$this->assertContains( '<option value="de_DE" lang="de" selected=\'selected\' data-installed="1">Deutsch</option>', $actual );
-		$this->assertContains( '<option value="it_IT" lang="it">Italiano</option>', $actual );
-		$this->assertContains( '<option value="ja_JP" lang="ja">日本語</option>', $actual );
+		$this->assertStringContainsString( 'id="foo"', $actual );
+		$this->assertStringContainsString( 'name="bar"', $actual );
+		$this->assertStringContainsString( '<option value="site-default" data-installed="1">Site Default</option>', $actual );
+		$this->assertStringContainsString( '<option value="" lang="en" data-installed="1">English (United States)</option>', $actual );
+		$this->assertStringContainsString( '<option value="de_DE" lang="de" selected=\'selected\' data-installed="1">Deutsch</option>', $actual );
+		$this->assertStringContainsString( '<option value="it_IT" lang="it">Italiano</option>', $actual );
+		$this->assertStringContainsString( '<option value="ja_JP" lang="ja">日本語</option>', $actual );
 	}
 
 	/**
@@ -148,7 +148,7 @@ class Tests_L10n extends WP_UnitTestCase {
 		);
 		$actual = wp_dropdown_languages( $args );
 
-		$this->assertNotContains( '<option value="" lang="en" data-installed="1">English (United States)</option>', $actual );
+		$this->assertStringNotContainsString( '<option value="" lang="en" data-installed="1">English (United States)</option>', $actual );
 	}
 
 	/**
@@ -165,12 +165,12 @@ class Tests_L10n extends WP_UnitTestCase {
 		);
 		$actual = wp_dropdown_languages( $args );
 
-		$this->assertContains( 'id="foo"', $actual );
-		$this->assertContains( 'name="bar"', $actual );
-		$this->assertContains( '<option value="" lang="en" data-installed="1" selected=\'selected\'>English (United States)</option>', $actual );
-		$this->assertContains( '<option value="de_DE" lang="de" data-installed="1">Deutsch</option>', $actual );
-		$this->assertContains( '<option value="it_IT" lang="it">Italiano</option>', $actual );
-		$this->assertContains( '<option value="ja_JP" lang="ja">日本語</option>', $actual );
+		$this->assertStringContainsString( 'id="foo"', $actual );
+		$this->assertStringContainsString( 'name="bar"', $actual );
+		$this->assertStringContainsString( '<option value="" lang="en" data-installed="1" selected=\'selected\'>English (United States)</option>', $actual );
+		$this->assertStringContainsString( '<option value="de_DE" lang="de" data-installed="1">Deutsch</option>', $actual );
+		$this->assertStringContainsString( '<option value="it_IT" lang="it">Italiano</option>', $actual );
+		$this->assertStringContainsString( '<option value="ja_JP" lang="ja">日本語</option>', $actual );
 	}
 
 	/**
@@ -188,13 +188,13 @@ class Tests_L10n extends WP_UnitTestCase {
 		);
 		$actual = wp_dropdown_languages( $args );
 
-		$this->assertContains( 'id="foo"', $actual );
-		$this->assertContains( 'name="bar"', $actual );
-		$this->assertContains( '<option value="site-default" data-installed="1">Site Default</option>', $actual );
-		$this->assertContains( '<option value="" lang="en" data-installed="1">English (United States)</option>', $actual );
-		$this->assertContains( '<option value="de_DE" lang="de">Deutsch</option>', $actual );
-		$this->assertContains( '<option value="it_IT" lang="it">Italiano</option>', $actual );
-		$this->assertContains( '<option value="ja_JP" lang="ja" selected=\'selected\' data-installed="1">日本語</option>', $actual );
+		$this->assertStringContainsString( 'id="foo"', $actual );
+		$this->assertStringContainsString( 'name="bar"', $actual );
+		$this->assertStringContainsString( '<option value="site-default" data-installed="1">Site Default</option>', $actual );
+		$this->assertStringContainsString( '<option value="" lang="en" data-installed="1">English (United States)</option>', $actual );
+		$this->assertStringContainsString( '<option value="de_DE" lang="de">Deutsch</option>', $actual );
+		$this->assertStringContainsString( '<option value="it_IT" lang="it">Italiano</option>', $actual );
+		$this->assertStringContainsString( '<option value="ja_JP" lang="ja" selected=\'selected\' data-installed="1">日本語</option>', $actual );
 	}
 
 	/**
@@ -211,12 +211,12 @@ class Tests_L10n extends WP_UnitTestCase {
 		);
 		$actual = wp_dropdown_languages( $args );
 
-		$this->assertContains( 'id="foo"', $actual );
-		$this->assertContains( 'name="bar"', $actual );
-		$this->assertContains( '<option value="" lang="en" data-installed="1">English (United States)</option>', $actual );
-		$this->assertContains( '<option value="de_DE" lang="de" data-installed="1">Deutsch</option>', $actual );
-		$this->assertContains( '<option value="it_IT" lang="it">Italiano</option>', $actual );
-		$this->assertContains( '<option value="ja_JP" lang="ja" selected=\'selected\'>日本語</option>', $actual );
+		$this->assertStringContainsString( 'id="foo"', $actual );
+		$this->assertStringContainsString( 'name="bar"', $actual );
+		$this->assertStringContainsString( '<option value="" lang="en" data-installed="1">English (United States)</option>', $actual );
+		$this->assertStringContainsString( '<option value="de_DE" lang="de" data-installed="1">Deutsch</option>', $actual );
+		$this->assertStringContainsString( '<option value="it_IT" lang="it">Italiano</option>', $actual );
+		$this->assertStringContainsString( '<option value="ja_JP" lang="ja" selected=\'selected\'>日本語</option>', $actual );
 	}
 
 	/**
diff --git a/tests/phpunit/tests/link/getNextCommentsLink.php b/tests/phpunit/tests/link/getNextCommentsLink.php
index 204b2057ff..459ad9d176 100644
--- a/tests/phpunit/tests/link/getNextCommentsLink.php
+++ b/tests/phpunit/tests/link/getNextCommentsLink.php
@@ -16,7 +16,7 @@ class Tests_Link_GetNextCommentsLink extends WP_UnitTestCase {
 
 		$link = get_next_comments_link( 'Next', 5 );
 
-		$this->assertContains( 'cpage=4', $link );
+		$this->assertStringContainsString( 'cpage=4', $link );
 
 		set_query_var( 'cpage', $cpage );
 	}
@@ -33,7 +33,7 @@ class Tests_Link_GetNextCommentsLink extends WP_UnitTestCase {
 
 		$link = get_next_comments_link( 'Next', 5 );
 
-		$this->assertContains( 'cpage=2', $link );
+		$this->assertStringContainsString( 'cpage=2', $link );
 
 		set_query_var( 'cpage', $cpage );
 	}
diff --git a/tests/phpunit/tests/link/getPreviousCommentsLink.php b/tests/phpunit/tests/link/getPreviousCommentsLink.php
index 6872f90e89..cda521a204 100644
--- a/tests/phpunit/tests/link/getPreviousCommentsLink.php
+++ b/tests/phpunit/tests/link/getPreviousCommentsLink.php
@@ -16,7 +16,7 @@ class Tests_Link_GetPreviousCommentsLink extends WP_UnitTestCase {
 
 		$link = get_previous_comments_link( 'Next' );
 
-		$this->assertContains( 'cpage=2', $link );
+		$this->assertStringContainsString( 'cpage=2', $link );
 
 		set_query_var( 'cpage', $cpage );
 	}
diff --git a/tests/phpunit/tests/link/getThePrivacyPolicyLink.php b/tests/phpunit/tests/link/getThePrivacyPolicyLink.php
index 36e9ccd577..97d321b805 100644
--- a/tests/phpunit/tests/link/getThePrivacyPolicyLink.php
+++ b/tests/phpunit/tests/link/getThePrivacyPolicyLink.php
@@ -80,7 +80,7 @@ class Tests_Link_GetThePrivacyPolicyLink extends WP_UnitTestCase {
 		$actual_link = get_the_privacy_policy_link();
 
 		$this->assertStringStartsWith( '<a', $actual_link );
-		$this->assertContains( self::$privacy_policy_url, $actual_link );
+		$this->assertStringContainsString( self::$privacy_policy_url, $actual_link );
 		$this->assertStringEndsWith( '>' . WP_TESTS_DOMAIN . ' Privacy Policy</a>', $actual_link );
 	}
 
@@ -94,7 +94,7 @@ class Tests_Link_GetThePrivacyPolicyLink extends WP_UnitTestCase {
 		$actual_link = get_the_privacy_policy_link( self::$before, self::$after );
 
 		$this->assertStringStartsWith( self::$before . '<a', $actual_link );
-		$this->assertContains( self::$privacy_policy_url, $actual_link );
+		$this->assertStringContainsString( self::$privacy_policy_url, $actual_link );
 		$this->assertStringEndsWith( '</a>' . self::$after, $actual_link );
 	}
 
diff --git a/tests/phpunit/tests/mail.php b/tests/phpunit/tests/mail.php
index d6b0f2d49d..c81ca448be 100644
--- a/tests/phpunit/tests/mail.php
+++ b/tests/phpunit/tests/mail.php
@@ -320,7 +320,7 @@ class Tests_Mail extends WP_UnitTestCase {
 			'Content-Type: text/html'
 		);
 
-		$this->assertNotContains( 'quoted-printable', $GLOBALS['phpmailer']->mock_sent[0]['header'] );
+		$this->assertStringNotContainsString( 'quoted-printable', $GLOBALS['phpmailer']->mock_sent[0]['header'] );
 	}
 
 	/**
diff --git a/tests/phpunit/tests/media.php b/tests/phpunit/tests/media.php
index 970df1d16c..1bc558c208 100644
--- a/tests/phpunit/tests/media.php
+++ b/tests/phpunit/tests/media.php
@@ -823,12 +823,12 @@ VIDEO;
 			)
 		);
 
-		$this->assertContains( 'src="https://example.com/foo.mp3', $actual );
-		$this->assertNotContains( 'loop', $actual );
-		$this->assertNotContains( 'autoplay', $actual );
-		$this->assertContains( 'preload="none"', $actual );
-		$this->assertContains( 'class="wp-audio-shortcode"', $actual );
-		$this->assertContains( 'style="width: 100%;"', $actual );
+		$this->assertStringContainsString( 'src="https://example.com/foo.mp3', $actual );
+		$this->assertStringNotContainsString( 'loop', $actual );
+		$this->assertStringNotContainsString( 'autoplay', $actual );
+		$this->assertStringContainsString( 'preload="none"', $actual );
+		$this->assertStringContainsString( 'class="wp-audio-shortcode"', $actual );
+		$this->assertStringContainsString( 'style="width: 100%;"', $actual );
 
 		$actual = wp_audio_shortcode(
 			array(
@@ -841,12 +841,12 @@ VIDEO;
 			)
 		);
 
-		$this->assertContains( 'src="https://example.com/foo.mp3', $actual );
-		$this->assertContains( 'loop="1"', $actual );
-		$this->assertContains( 'autoplay="1"', $actual );
-		$this->assertContains( 'preload="1"', $actual );
-		$this->assertContains( 'class="foobar"', $actual );
-		$this->assertContains( 'style="padding:0;"', $actual );
+		$this->assertStringContainsString( 'src="https://example.com/foo.mp3', $actual );
+		$this->assertStringContainsString( 'loop="1"', $actual );
+		$this->assertStringContainsString( 'autoplay="1"', $actual );
+		$this->assertStringContainsString( 'preload="1"', $actual );
+		$this->assertStringContainsString( 'class="foobar"', $actual );
+		$this->assertStringContainsString( 'style="padding:0;"', $actual );
 	}
 
 	/**
@@ -928,13 +928,13 @@ VIDEO;
 			)
 		);
 
-		$this->assertContains( 'src="https://example.com/foo.mp4', $actual );
-		$this->assertNotContains( 'loop', $actual );
-		$this->assertNotContains( 'autoplay', $actual );
-		$this->assertContains( 'preload="metadata"', $actual );
-		$this->assertContains( 'width="640"', $actual );
-		$this->assertContains( 'height="360"', $actual );
-		$this->assertContains( 'class="wp-video-shortcode"', $actual );
+		$this->assertStringContainsString( 'src="https://example.com/foo.mp4', $actual );
+		$this->assertStringNotContainsString( 'loop', $actual );
+		$this->assertStringNotContainsString( 'autoplay', $actual );
+		$this->assertStringContainsString( 'preload="metadata"', $actual );
+		$this->assertStringContainsString( 'width="640"', $actual );
+		$this->assertStringContainsString( 'height="360"', $actual );
+		$this->assertStringContainsString( 'class="wp-video-shortcode"', $actual );
 
 		$actual = wp_video_shortcode(
 			array(
@@ -949,14 +949,14 @@ VIDEO;
 			)
 		);
 
-		$this->assertContains( 'src="https://example.com/foo.mp4', $actual );
-		$this->assertContains( 'poster="https://example.com/foo.png', $actual );
-		$this->assertContains( 'loop="1"', $actual );
-		$this->assertContains( 'autoplay="1"', $actual );
-		$this->assertContains( 'preload="1"', $actual );
-		$this->assertContains( 'width="123"', $actual );
-		$this->assertContains( 'height="456"', $actual );
-		$this->assertContains( 'class="foobar"', $actual );
+		$this->assertStringContainsString( 'src="https://example.com/foo.mp4', $actual );
+		$this->assertStringContainsString( 'poster="https://example.com/foo.png', $actual );
+		$this->assertStringContainsString( 'loop="1"', $actual );
+		$this->assertStringContainsString( 'autoplay="1"', $actual );
+		$this->assertStringContainsString( 'preload="1"', $actual );
+		$this->assertStringContainsString( 'width="123"', $actual );
+		$this->assertStringContainsString( 'height="456"', $actual );
+		$this->assertStringContainsString( 'class="foobar"', $actual );
 	}
 
 	/**
@@ -970,7 +970,7 @@ VIDEO;
 			)
 		);
 
-		$this->assertNotContains( 'feature=youtu.be', $actual );
+		$this->assertStringNotContainsString( 'feature=youtu.be', $actual );
 	}
 
 	/**
@@ -984,7 +984,7 @@ VIDEO;
 			)
 		);
 
-		$this->assertContains( 'src="https://www.youtube.com/watch?v=72xdCU__XCk', $actual );
+		$this->assertStringContainsString( 'src="https://www.youtube.com/watch?v=72xdCU__XCk', $actual );
 	}
 
 	/**
@@ -998,8 +998,8 @@ VIDEO;
 			)
 		);
 
-		$this->assertContains( 'src="https://vimeo.com/76979871', $actual );
-		$this->assertNotContains( 'blah=meh', $actual );
+		$this->assertStringContainsString( 'src="https://vimeo.com/76979871', $actual );
+		$this->assertStringNotContainsString( 'blah=meh', $actual );
 	}
 
 	/**
@@ -1013,7 +1013,7 @@ VIDEO;
 			)
 		);
 
-		$this->assertContains( 'src="https://vimeo.com/76979871?loop=0', $actual );
+		$this->assertStringContainsString( 'src="https://vimeo.com/76979871?loop=0', $actual );
 	}
 
 	/**
@@ -1028,7 +1028,7 @@ VIDEO;
 			)
 		);
 
-		$this->assertContains( 'src="https://vimeo.com/76979871?loop=1', $actual );
+		$this->assertStringContainsString( 'src="https://vimeo.com/76979871?loop=1', $actual );
 	}
 
 	/**
@@ -2862,7 +2862,7 @@ EOF;
 		$img = '<img src="example.png" alt=" width="300" height="225" />';
 		$img = wp_img_tag_add_loading_attr( $img, 'test' );
 
-		$this->assertContains( ' loading="lazy"', $img );
+		$this->assertStringContainsString( ' loading="lazy"', $img );
 	}
 
 	/**
@@ -2873,7 +2873,7 @@ EOF;
 		$img = '<img alt=" width="300" height="225" />';
 		$img = wp_img_tag_add_loading_attr( $img, 'test' );
 
-		$this->assertNotContains( ' loading=', $img );
+		$this->assertStringNotContainsString( ' loading=', $img );
 	}
 
 	/**
@@ -2884,11 +2884,11 @@ EOF;
 		$img = "<img src='example.png' alt=' width='300' height='225' />";
 		$img = wp_img_tag_add_loading_attr( $img, 'test' );
 
-		$this->assertNotContains( ' loading=', $img );
+		$this->assertStringNotContainsString( ' loading=', $img );
 
 		// Test specifically that the attribute is not there with double-quotes,
 		// to avoid regressions.
-		$this->assertNotContains( ' loading="lazy"', $img );
+		$this->assertStringNotContainsString( ' loading="lazy"', $img );
 	}
 
 	/**
@@ -2899,7 +2899,7 @@ EOF;
 		$img = '<img src="example.png" alt=" width="300" height="225" />';
 		add_filter( 'wp_img_tag_add_loading_attr', '__return_false' );
 
-		$this->assertNotContains( ' loading=', $img );
+		$this->assertStringNotContainsString( ' loading=', $img );
 	}
 
 	/**
@@ -2909,7 +2909,7 @@ EOF;
 		$iframe = '<iframe src="https://www.example.com" width="640" height="360"></iframe>';
 		$iframe = wp_iframe_tag_add_loading_attr( $iframe, 'test' );
 
-		$this->assertContains( ' loading="lazy"', $iframe );
+		$this->assertStringContainsString( ' loading="lazy"', $iframe );
 	}
 
 	/**
@@ -2919,7 +2919,7 @@ EOF;
 		$iframe = '<iframe width="640" height="360"></iframe>';
 		$iframe = wp_iframe_tag_add_loading_attr( $iframe, 'test' );
 
-		$this->assertNotContains( ' loading=', $iframe );
+		$this->assertStringNotContainsString( ' loading=', $iframe );
 	}
 
 	/**
@@ -2929,11 +2929,11 @@ EOF;
 		$iframe = "<iframe src='https://www.example.com' width='640' height='360'></iframe>";
 		$iframe = wp_iframe_tag_add_loading_attr( $iframe, 'test' );
 
-		$this->assertNotContains( ' loading=', $iframe );
+		$this->assertStringNotContainsString( ' loading=', $iframe );
 
 		// Test specifically that the attribute is not there with double-quotes,
 		// to avoid regressions.
-		$this->assertNotContains( ' loading="lazy"', $iframe );
+		$this->assertStringNotContainsString( ' loading="lazy"', $iframe );
 	}
 
 	/**
@@ -2944,7 +2944,7 @@ EOF;
 		add_filter( 'wp_iframe_tag_add_loading_attr', '__return_false' );
 		$iframe = wp_iframe_tag_add_loading_attr( $iframe, 'test' );
 
-		$this->assertNotContains( ' loading=', $iframe );
+		$this->assertStringNotContainsString( ' loading=', $iframe );
 	}
 
 	/**
@@ -2956,7 +2956,7 @@ EOF;
 		$iframe   = wp_filter_oembed_result( $fallback . $iframe, (object) array( 'type' => 'rich' ), 'https://www.example.com' );
 		$iframe   = wp_iframe_tag_add_loading_attr( $iframe, 'test' );
 
-		$this->assertNotContains( ' loading=', $iframe );
+		$this->assertStringNotContainsString( ' loading=', $iframe );
 	}
 
 	/**
@@ -2966,7 +2966,7 @@ EOF;
 	function test_wp_get_attachment_image_loading() {
 		$img = wp_get_attachment_image( self::$large_id );
 
-		$this->assertContains( ' loading="lazy"', $img );
+		$this->assertStringContainsString( ' loading="lazy"', $img );
 	}
 
 	/**
@@ -2978,7 +2978,7 @@ EOF;
 		$img = wp_get_attachment_image( self::$large_id );
 
 		// There should not be any loading attribute in this case.
-		$this->assertNotContains( ' loading=', $img );
+		$this->assertStringNotContainsString( ' loading=', $img );
 	}
 
 	/**
@@ -2993,7 +2993,7 @@ EOF;
 		$img = wp_get_attachment_image( self::$large_id, 'thumbnail', false, array( 'loading' => false ) );
 
 		// There should not be any loading attribute in this case.
-		$this->assertNotContains( ' loading=', $img );
+		$this->assertStringNotContainsString( ' loading=', $img );
 	}
 
 	/**
@@ -3116,7 +3116,7 @@ EOF;
 				'ids' => self::$large_id,
 			)
 		);
-		$this->assertContains( '?attachment_id=', $actual );
+		$this->assertStringContainsString( '?attachment_id=', $actual );
 
 		// File: Links to image file URL.
 		$actual = gallery_shortcode(
@@ -3134,7 +3134,7 @@ EOF;
 				'link' => 'none',
 			)
 		);
-		$this->assertNotContains( '<a ', $actual );
+		$this->assertStringNotContainsString( '<a ', $actual );
 	}
 
 	/**
diff --git a/tests/phpunit/tests/meta/query.php b/tests/phpunit/tests/meta/query.php
index 5b3815d47d..7dd2535a5b 100644
--- a/tests/phpunit/tests/meta/query.php
+++ b/tests/phpunit/tests/meta/query.php
@@ -900,8 +900,8 @@ class Tests_Meta_Query extends WP_UnitTestCase {
 		);
 
 		$sql = $query->get_sql( 'post', $wpdb->posts, 'ID', $this );
-		$this->assertNotContains( "{$wpdb->postmeta}.meta_key = 'exclude'\nOR", $sql['where'] );
-		$this->assertContains( "{$wpdb->postmeta}.post_id IS NULL", $sql['where'] );
+		$this->assertStringNotContainsString( "{$wpdb->postmeta}.meta_key = 'exclude'\nOR", $sql['where'] );
+		$this->assertStringContainsString( "{$wpdb->postmeta}.post_id IS NULL", $sql['where'] );
 	}
 
 	public function test_empty_compare() {
@@ -926,7 +926,7 @@ class Tests_Meta_Query extends WP_UnitTestCase {
 
 		// Use regex because we don't care about the whitespace before OR.
 		$this->assertRegExp( "/{$wpdb->postmeta}\.meta_key = \'exclude\'\s+OR/", $sql['where'] );
-		$this->assertNotContains( "{$wpdb->postmeta}.post_id IS NULL", $sql['where'] );
+		$this->assertStringNotContainsString( "{$wpdb->postmeta}.post_id IS NULL", $sql['where'] );
 	}
 
 	/**
diff --git a/tests/phpunit/tests/multisite/site.php b/tests/phpunit/tests/multisite/site.php
index 5e87c61c2c..557da8c06a 100644
--- a/tests/phpunit/tests/multisite/site.php
+++ b/tests/phpunit/tests/multisite/site.php
@@ -514,8 +514,8 @@ if ( is_multisite() ) :
 			$post    = get_post( $post_id );
 			$content = apply_filters( 'the_content', $post->post_content );
 
-			$this->assertNotContains( $post_data['post_title'], $content );
-			$this->assertNotContains( "src=\"{$spam_embed_url}#?", $content );
+			$this->assertStringNotContainsString( $post_data['post_title'], $content );
+			$this->assertStringNotContainsString( "src=\"{$spam_embed_url}#?", $content );
 		}
 
 		function test_update_blog_status_make_spam_blog_action() {
diff --git a/tests/phpunit/tests/oembed/WpEmbed.php b/tests/phpunit/tests/oembed/WpEmbed.php
index b01ca75eff..83ca8b58eb 100644
--- a/tests/phpunit/tests/oembed/WpEmbed.php
+++ b/tests/phpunit/tests/oembed/WpEmbed.php
@@ -54,7 +54,7 @@ class Tests_WP_Embed extends WP_UnitTestCase {
 		unset( $GLOBALS['post'] );
 		unset( $GLOBALS['message'] );
 
-		$this->assertContains( $url, $actual );
+		$this->assertStringContainsString( $url, $actual );
 	}
 
 	public function test_wp_maybe_load_embeds() {
diff --git a/tests/phpunit/tests/oembed/template.php b/tests/phpunit/tests/oembed/template.php
index 9d863b3da9..6f9580229f 100644
--- a/tests/phpunit/tests/oembed/template.php
+++ b/tests/phpunit/tests/oembed/template.php
@@ -300,6 +300,6 @@ class Tests_Embed_Template extends WP_UnitTestCase {
 	 * @ticket 34698
 	 */
 	function test_js_no_ampersands() {
-		$this->assertNotContains( '&', file_get_contents( ABSPATH . WPINC . '/js/wp-embed.js' ) );
+		$this->assertStringNotContainsString( '&', file_get_contents( ABSPATH . WPINC . '/js/wp-embed.js' ) );
 	}
 }
diff --git a/tests/phpunit/tests/post.php b/tests/phpunit/tests/post.php
index 7e87f29eae..5881165e13 100644
--- a/tests/phpunit/tests/post.php
+++ b/tests/phpunit/tests/post.php
@@ -498,7 +498,7 @@ class Tests_Post extends WP_UnitTestCase {
 
 		$post = get_post( $p );
 
-		$this->assertContains( 'wptests_pt=' . $p, $post->guid );
+		$this->assertStringContainsString( 'wptests_pt=' . $p, $post->guid );
 	}
 
 	/**
@@ -924,8 +924,8 @@ class Tests_Post extends WP_UnitTestCase {
 		$term  = reset( $terms );
 
 		foreach ( $matches[1] as $url ) {
-			$this->assertContains( 'tag_ID=' . $term->term_id, $url );
-			$this->assertContains( 'post_type=new_post_type', $url );
+			$this->assertStringContainsString( 'tag_ID=' . $term->term_id, $url );
+			$this->assertStringContainsString( 'post_type=new_post_type', $url );
 		}
 	}
 
diff --git a/tests/phpunit/tests/post/attachments.php b/tests/phpunit/tests/post/attachments.php
index 43ed61d07d..9bab31b771 100644
--- a/tests/phpunit/tests/post/attachments.php
+++ b/tests/phpunit/tests/post/attachments.php
@@ -508,7 +508,7 @@ class Tests_Post_Attachments extends WP_UnitTestCase {
 	public function test_wp_mime_type_icon() {
 		$icon = wp_mime_type_icon();
 
-		$this->assertContains( 'images/media/default.png', $icon );
+		$this->assertStringContainsString( 'images/media/default.png', $icon );
 	}
 
 	/**
@@ -517,6 +517,6 @@ class Tests_Post_Attachments extends WP_UnitTestCase {
 	public function test_wp_mime_type_icon_video() {
 		$icon = wp_mime_type_icon( 'video/mp4' );
 
-		$this->assertContains( 'images/media/video.png', $icon );
+		$this->assertStringContainsString( 'images/media/video.png', $icon );
 	}
 }
diff --git a/tests/phpunit/tests/post/getPages.php b/tests/phpunit/tests/post/getPages.php
index e12a07d941..5ccc27c6ef 100644
--- a/tests/phpunit/tests/post/getPages.php
+++ b/tests/phpunit/tests/post/getPages.php
@@ -645,7 +645,7 @@ class Tests_Post_GetPages extends WP_UnitTestCase {
 
 		$this->assertNotEmpty( $output );
 		$this->assertSame( 2, substr_count( $output, 'class="page_item ' ) );
-		$this->assertContains( 'current_page_item', $output );
+		$this->assertStringContainsString( 'current_page_item', $output );
 		$this->assertSame( 1, substr_count( $output, 'current_page_item' ) );
 
 		_unregister_post_type( $type );
diff --git a/tests/phpunit/tests/post/getPostsByAuthorSql.php b/tests/phpunit/tests/post/getPostsByAuthorSql.php
index 6a6a3b366f..f030738f0d 100644
--- a/tests/phpunit/tests/post/getPostsByAuthorSql.php
+++ b/tests/phpunit/tests/post/getPostsByAuthorSql.php
@@ -7,17 +7,17 @@ class Tests_Post_GetPostsByAuthorSql extends WP_UnitTestCase {
 
 	public function test_post_type_post() {
 		$maybe_string = get_posts_by_author_sql( 'post' );
-		$this->assertContains( "post_type = 'post'", $maybe_string );
+		$this->assertStringContainsString( "post_type = 'post'", $maybe_string );
 	}
 
 	public function test_post_type_page() {
 		$maybe_string = get_posts_by_author_sql( 'page' );
-		$this->assertContains( "post_type = 'page'", $maybe_string );
+		$this->assertStringContainsString( "post_type = 'page'", $maybe_string );
 	}
 
 	public function test_non_existent_post_type() {
 		$maybe_string = get_posts_by_author_sql( 'non_existent_post_type' );
-		$this->assertContains( '1 = 0', $maybe_string );
+		$this->assertStringContainsString( '1 = 0', $maybe_string );
 	}
 
 	public function test_multiple_post_types() {
@@ -25,8 +25,8 @@ class Tests_Post_GetPostsByAuthorSql extends WP_UnitTestCase {
 		register_post_type( 'bar' );
 
 		$maybe_string = get_posts_by_author_sql( array( 'foo', 'bar' ) );
-		$this->assertContains( "post_type = 'foo'", $maybe_string );
-		$this->assertContains( "post_type = 'bar'", $maybe_string );
+		$this->assertStringContainsString( "post_type = 'foo'", $maybe_string );
+		$this->assertStringContainsString( "post_type = 'bar'", $maybe_string );
 
 		_unregister_post_type( 'foo' );
 		_unregister_post_type( 'bar' );
@@ -44,17 +44,17 @@ class Tests_Post_GetPostsByAuthorSql extends WP_UnitTestCase {
 
 	public function test_post_type_clause_should_be_included_when_full_is_true() {
 		$maybe_string = get_posts_by_author_sql( 'post', true );
-		$this->assertContains( "post_type = 'post'", $maybe_string );
+		$this->assertStringContainsString( "post_type = 'post'", $maybe_string );
 	}
 
 	public function test_post_type_clause_should_be_included_when_full_is_false() {
 		$maybe_string = get_posts_by_author_sql( 'post', false );
-		$this->assertContains( "post_type = 'post'", $maybe_string );
+		$this->assertStringContainsString( "post_type = 'post'", $maybe_string );
 	}
 
 	public function test_post_author_should_create_post_author_clause() {
 		$maybe_string = get_posts_by_author_sql( 'post', true, 1 );
-		$this->assertContains( 'post_author = 1', $maybe_string );
+		$this->assertStringContainsString( 'post_author = 1', $maybe_string );
 	}
 
 	public function test_public_only_true_should_not_allow_any_private_posts_for_loggedin_user() {
@@ -63,7 +63,7 @@ class Tests_Post_GetPostsByAuthorSql extends WP_UnitTestCase {
 		wp_set_current_user( $u );
 
 		$maybe_string = get_posts_by_author_sql( 'post', true, $u, true );
-		$this->assertNotContains( "post_status = 'private'", $maybe_string );
+		$this->assertStringNotContainsString( "post_status = 'private'", $maybe_string );
 
 		wp_set_current_user( $current_user );
 	}
@@ -84,7 +84,7 @@ class Tests_Post_GetPostsByAuthorSql extends WP_UnitTestCase {
 		wp_set_current_user( $u );
 
 		$maybe_string = get_posts_by_author_sql( 'post', true, $u, false );
-		$this->assertContains( "post_status = 'private'", $maybe_string );
+		$this->assertStringContainsString( "post_status = 'private'", $maybe_string );
 
 		wp_set_current_user( $current_user );
 	}
@@ -96,7 +96,7 @@ class Tests_Post_GetPostsByAuthorSql extends WP_UnitTestCase {
 		wp_set_current_user( $u1 );
 
 		$maybe_string = get_posts_by_author_sql( 'post', true, $u2, false );
-		$this->assertNotContains( "post_status = 'private'", $maybe_string );
+		$this->assertStringNotContainsString( "post_status = 'private'", $maybe_string );
 
 		wp_set_current_user( $current_user );
 	}
@@ -107,8 +107,8 @@ class Tests_Post_GetPostsByAuthorSql extends WP_UnitTestCase {
 		wp_set_current_user( $u );
 
 		$maybe_string = get_posts_by_author_sql( 'post', true, $u, false );
-		$this->assertContains( "post_status = 'private'", $maybe_string );
-		$this->assertContains( "post_author = $u", $maybe_string );
+		$this->assertStringContainsString( "post_status = 'private'", $maybe_string );
+		$this->assertStringContainsString( "post_author = $u", $maybe_string );
 
 		wp_set_current_user( $current_user );
 	}
@@ -119,8 +119,8 @@ class Tests_Post_GetPostsByAuthorSql extends WP_UnitTestCase {
 		wp_set_current_user( $u );
 
 		$maybe_string = get_posts_by_author_sql( 'post', true, null, false );
-		$this->assertContains( "post_status = 'private'", $maybe_string );
-		$this->assertNotContains( 'post_author', $maybe_string );
+		$this->assertStringContainsString( "post_status = 'private'", $maybe_string );
+		$this->assertStringNotContainsString( 'post_author', $maybe_string );
 
 		wp_set_current_user( $current_user );
 	}
@@ -139,9 +139,9 @@ class Tests_Post_GetPostsByAuthorSql extends WP_UnitTestCase {
 
 		$editor_role->remove_cap( 'read_private_baz' );
 
-		$this->assertNotContains( "post_type = 'foo' AND ( post_status = 'publish' OR post_status = 'private' )", $maybe_string );
-		$this->assertNotContains( "post_type = 'bar' AND ( post_status = 'publish' OR post_status = 'private' )", $maybe_string );
-		$this->assertContains( "post_type = 'baz' AND ( post_status = 'publish' OR post_status = 'private' )", $maybe_string );
+		$this->assertStringNotContainsString( "post_type = 'foo' AND ( post_status = 'publish' OR post_status = 'private' )", $maybe_string );
+		$this->assertStringNotContainsString( "post_type = 'bar' AND ( post_status = 'publish' OR post_status = 'private' )", $maybe_string );
+		$this->assertStringContainsString( "post_type = 'baz' AND ( post_status = 'publish' OR post_status = 'private' )", $maybe_string );
 
 		_unregister_post_type( 'foo' );
 		_unregister_post_type( 'bar' );
diff --git a/tests/phpunit/tests/post/getTheContent.php b/tests/phpunit/tests/post/getTheContent.php
index 54b8fe318e..91f0b621f3 100644
--- a/tests/phpunit/tests/post/getTheContent.php
+++ b/tests/phpunit/tests/post/getTheContent.php
@@ -19,7 +19,7 @@ class Tests_Post_GetTheContent extends WP_UnitTestCase {
 			$found = get_the_content( 'Ping' );
 		}
 
-		$this->assertContains( '>Ping<', $found );
+		$this->assertStringContainsString( '>Ping<', $found );
 	}
 
 	/**
@@ -38,7 +38,7 @@ class Tests_Post_GetTheContent extends WP_UnitTestCase {
 			$found = get_the_content( null, true );
 		}
 
-		$this->assertNotContains( 'Foo', $found );
+		$this->assertStringNotContainsString( 'Foo', $found );
 	}
 
 	/**
diff --git a/tests/phpunit/tests/post/output.php b/tests/phpunit/tests/post/output.php
index 62f5db9ecf..f5534d535f 100644
--- a/tests/phpunit/tests/post/output.php
+++ b/tests/phpunit/tests/post/output.php
@@ -305,11 +305,11 @@ EOF;
 
 		foreach ( array( true, false ) as $strip_teaser ) {
 			$actual = get_echo( 'the_content', array( null, $strip_teaser ) );
-			$this->assertContains( 'Teaser part', $actual );
-			$this->assertContains( 'Read More</a>', $actual );
-			$this->assertNotContains( '<!--more-->', $actual );
-			$this->assertNotContains( 'wp:more', $actual );
-			$this->assertNotContains( 'wp:paragraph', $actual );
+			$this->assertStringContainsString( 'Teaser part', $actual );
+			$this->assertStringContainsString( 'Read More</a>', $actual );
+			$this->assertStringNotContainsString( '<!--more-->', $actual );
+			$this->assertStringNotContainsString( 'wp:more', $actual );
+			$this->assertStringNotContainsString( 'wp:paragraph', $actual );
 		}
 	}
 
@@ -346,12 +346,12 @@ EOF;
 
 		foreach ( array( true, false ) as $strip_teaser ) {
 			$actual = get_echo( 'the_content', array( null, $strip_teaser ) );
-			$this->assertContains( 'Teaser part', $actual );
-			$this->assertContains( '(more&hellip;)</span></a>', $actual );
-			$this->assertNotContains( '<!--more-->', $actual );
-			$this->assertNotContains( '<!--noteaser-->', $actual ); // We placed the noteaser tag below the more tag.
-			$this->assertNotContains( 'wp:more', $actual );
-			$this->assertNotContains( 'wp:paragraph', $actual );
+			$this->assertStringContainsString( 'Teaser part', $actual );
+			$this->assertStringContainsString( '(more&hellip;)</span></a>', $actual );
+			$this->assertStringNotContainsString( '<!--more-->', $actual );
+			$this->assertStringNotContainsString( '<!--noteaser-->', $actual ); // We placed the noteaser tag below the more tag.
+			$this->assertStringNotContainsString( 'wp:more', $actual );
+			$this->assertStringNotContainsString( 'wp:paragraph', $actual );
 		}
 	}
 }
diff --git a/tests/phpunit/tests/post/query.php b/tests/phpunit/tests/post/query.php
index 6ccf69f534..6622813ef9 100644
--- a/tests/phpunit/tests/post/query.php
+++ b/tests/phpunit/tests/post/query.php
@@ -319,13 +319,13 @@ class Tests_Post_Query extends WP_UnitTestCase {
 		$this->assertNotContains( 'auto-draft', $statuses3 );
 
 		$q1 = new WP_Query( array( 'post_status' => 'any' ) );
-		$this->assertContains( "post_status <> 'auto-draft'", $q1->request );
+		$this->assertStringContainsString( "post_status <> 'auto-draft'", $q1->request );
 
 		$q2 = new WP_Query( array( 'post_status' => 'any, auto-draft' ) );
-		$this->assertNotContains( "post_status <> 'auto-draft'", $q2->request );
+		$this->assertStringNotContainsString( "post_status <> 'auto-draft'", $q2->request );
 
 		$q3 = new WP_Query( array( 'post_status' => array( 'any', 'auto-draft' ) ) );
-		$this->assertNotContains( "post_status <> 'auto-draft'", $q3->request );
+		$this->assertStringNotContainsString( "post_status <> 'auto-draft'", $q3->request );
 	}
 
 	/**
@@ -342,23 +342,23 @@ class Tests_Post_Query extends WP_UnitTestCase {
 				),
 			)
 		);
-		$this->assertContains(
+		$this->assertStringContainsString(
 			"ORDER BY $wpdb->posts.post_type DESC, $wpdb->posts.post_name ASC",
 			$q1->request
 		);
 
 		$q2 = new WP_Query( array( 'orderby' => array() ) );
-		$this->assertNotContains( 'ORDER BY', $q2->request );
-		$this->assertNotContains( 'ORDER', $q2->request );
+		$this->assertStringNotContainsString( 'ORDER BY', $q2->request );
+		$this->assertStringNotContainsString( 'ORDER', $q2->request );
 
 		$q3 = new WP_Query( array( 'post_type' => 'post' ) );
-		$this->assertContains(
+		$this->assertStringContainsString(
 			"ORDER BY $wpdb->posts.post_date DESC",
 			$q3->request
 		);
 
 		$q4 = new WP_Query( array( 'post_type' => 'post' ) );
-		$this->assertContains(
+		$this->assertStringContainsString(
 			"ORDER BY $wpdb->posts.post_date DESC",
 			$q4->request
 		);
@@ -377,7 +377,7 @@ class Tests_Post_Query extends WP_UnitTestCase {
 				),
 			)
 		);
-		$this->assertContains(
+		$this->assertStringContainsString(
 			"ORDER BY $wpdb->posts.post_type DESC",
 			$q1->request
 		);
@@ -388,7 +388,7 @@ class Tests_Post_Query extends WP_UnitTestCase {
 				'order'   => 'foo',
 			)
 		);
-		$this->assertContains(
+		$this->assertStringContainsString(
 			"ORDER BY $wpdb->posts.post_title DESC",
 			$q2->request
 		);
@@ -398,7 +398,7 @@ class Tests_Post_Query extends WP_UnitTestCase {
 				'order' => 'asc',
 			)
 		);
-		$this->assertContains(
+		$this->assertStringContainsString(
 			"ORDER BY $wpdb->posts.post_date ASC",
 			$q3->request
 		);
@@ -410,33 +410,33 @@ class Tests_Post_Query extends WP_UnitTestCase {
 	function test_orderby() {
 		// 'rand' is a valid value.
 		$q = new WP_Query( array( 'orderby' => 'rand' ) );
-		$this->assertContains( 'ORDER BY RAND()', $q->request );
-		$this->assertNotContains( 'ASC', $q->request );
-		$this->assertNotContains( 'DESC', $q->request );
+		$this->assertStringContainsString( 'ORDER BY RAND()', $q->request );
+		$this->assertStringNotContainsString( 'ASC', $q->request );
+		$this->assertStringNotContainsString( 'DESC', $q->request );
 
 		// This isn't allowed.
 		$q2 = new WP_Query( array( 'order' => 'rand' ) );
-		$this->assertContains( 'ORDER BY', $q2->request );
-		$this->assertNotContains( 'RAND()', $q2->request );
-		$this->assertContains( 'DESC', $q2->request );
+		$this->assertStringContainsString( 'ORDER BY', $q2->request );
+		$this->assertStringNotContainsString( 'RAND()', $q2->request );
+		$this->assertStringContainsString( 'DESC', $q2->request );
 
 		// 'none' is a valid value.
 		$q3 = new WP_Query( array( 'orderby' => 'none' ) );
-		$this->assertNotContains( 'ORDER BY', $q3->request );
-		$this->assertNotContains( 'DESC', $q3->request );
-		$this->assertNotContains( 'ASC', $q3->request );
+		$this->assertStringNotContainsString( 'ORDER BY', $q3->request );
+		$this->assertStringNotContainsString( 'DESC', $q3->request );
+		$this->assertStringNotContainsString( 'ASC', $q3->request );
 
 		// False is a valid value.
 		$q4 = new WP_Query( array( 'orderby' => false ) );
-		$this->assertNotContains( 'ORDER BY', $q4->request );
-		$this->assertNotContains( 'DESC', $q4->request );
-		$this->assertNotContains( 'ASC', $q4->request );
+		$this->assertStringNotContainsString( 'ORDER BY', $q4->request );
+		$this->assertStringNotContainsString( 'DESC', $q4->request );
+		$this->assertStringNotContainsString( 'ASC', $q4->request );
 
 		// Empty array() is a valid value.
 		$q5 = new WP_Query( array( 'orderby' => array() ) );
-		$this->assertNotContains( 'ORDER BY', $q5->request );
-		$this->assertNotContains( 'DESC', $q5->request );
-		$this->assertNotContains( 'ASC', $q5->request );
+		$this->assertStringNotContainsString( 'ORDER BY', $q5->request );
+		$this->assertStringNotContainsString( 'DESC', $q5->request );
+		$this->assertStringNotContainsString( 'ASC', $q5->request );
 	}
 
 	/**
@@ -449,7 +449,7 @@ class Tests_Post_Query extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( 'ORDER BY RAND(5)', $q->request );
+		$this->assertStringContainsString( 'ORDER BY RAND(5)', $q->request );
 	}
 
 	/**
@@ -462,7 +462,7 @@ class Tests_Post_Query extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertNotContains( 'ORDER BY RAND', $q->request );
+		$this->assertStringNotContainsString( 'ORDER BY RAND', $q->request );
 	}
 
 	/**
@@ -475,7 +475,7 @@ class Tests_Post_Query extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( 'ORDER BY RAND(5)', $q->request );
+		$this->assertStringContainsString( 'ORDER BY RAND(5)', $q->request );
 	}
 
 	/**
diff --git a/tests/phpunit/tests/post/template.php b/tests/phpunit/tests/post/template.php
index f725121bbc..3e3cbfe3ff 100644
--- a/tests/phpunit/tests/post/template.php
+++ b/tests/phpunit/tests/post/template.php
@@ -237,7 +237,7 @@ NO;
 		);
 
 		// Should contain page ID by default.
-		$this->assertContains( 'value="' . $p . '"', $found );
+		$this->assertStringContainsString( 'value="' . $p . '"', $found );
 	}
 
 	/**
@@ -257,7 +257,7 @@ NO;
 			)
 		);
 
-		$this->assertContains( 'value="' . $p . '"', $found );
+		$this->assertStringContainsString( 'value="' . $p . '"', $found );
 	}
 
 	/**
@@ -278,7 +278,7 @@ NO;
 			)
 		);
 
-		$this->assertContains( 'value="foo"', $found );
+		$this->assertStringContainsString( 'value="foo"', $found );
 	}
 
 	/**
@@ -299,7 +299,7 @@ NO;
 			)
 		);
 
-		$this->assertContains( 'value="' . $p . '"', $found );
+		$this->assertStringContainsString( 'value="' . $p . '"', $found );
 	}
 
 	/**
diff --git a/tests/phpunit/tests/privacy/wpPrivacyGeneratePersonalDataExportGroupHtml.php b/tests/phpunit/tests/privacy/wpPrivacyGeneratePersonalDataExportGroupHtml.php
index badf0ea0d9..f85186d0c5 100644
--- a/tests/phpunit/tests/privacy/wpPrivacyGeneratePersonalDataExportGroupHtml.php
+++ b/tests/phpunit/tests/privacy/wpPrivacyGeneratePersonalDataExportGroupHtml.php
@@ -42,8 +42,8 @@ class Tests_Privacy_wpPrivacyGeneratePersonalDataExportGroupHtml extends WP_Unit
 		$actual                = wp_privacy_generate_personal_data_export_group_html( $data, 'test-data-group', 2 );
 		$expected_table_markup = '<table><tbody><tr><th>Field 1 Name</th><td>Field 1 Value</td></tr><tr><th>Field 2 Name</th><td>Field 2 Value</td></tr></tbody></table>';
 
-		$this->assertContains( '<h2 id="test-data-group-test-data-group">Test Data Group</h2>', $actual );
-		$this->assertContains( $expected_table_markup, $actual );
+		$this->assertStringContainsString( '<h2 id="test-data-group-test-data-group">Test Data Group</h2>', $actual );
+		$this->assertStringContainsString( $expected_table_markup, $actual );
 	}
 
 	/**
@@ -81,11 +81,11 @@ class Tests_Privacy_wpPrivacyGeneratePersonalDataExportGroupHtml extends WP_Unit
 
 		$actual = wp_privacy_generate_personal_data_export_group_html( $data, 'test-data-group', 2 );
 
-		$this->assertContains( '<h2 id="test-data-group-test-data-group">Test Data Group', $actual );
-		$this->assertContains( '<td>Field 1 Value', $actual );
-		$this->assertContains( '<td>Another Field 1 Value', $actual );
-		$this->assertContains( '<td>Field 2 Value', $actual );
-		$this->assertContains( '<td>Another Field 2 Value', $actual );
+		$this->assertStringContainsString( '<h2 id="test-data-group-test-data-group">Test Data Group', $actual );
+		$this->assertStringContainsString( '<td>Field 1 Value', $actual );
+		$this->assertStringContainsString( '<td>Another Field 1 Value', $actual );
+		$this->assertStringContainsString( '<td>Field 2 Value', $actual );
+		$this->assertStringContainsString( '<td>Another Field 2 Value', $actual );
 		$this->assertSame( 2, substr_count( $actual, '<th>Field 1 Name' ) );
 		$this->assertSame( 2, substr_count( $actual, '<th>Field 2 Name' ) );
 		$this->assertSame( 4, substr_count( $actual, '<tr>' ) );
@@ -119,9 +119,9 @@ class Tests_Privacy_wpPrivacyGeneratePersonalDataExportGroupHtml extends WP_Unit
 
 		$actual = wp_privacy_generate_personal_data_export_group_html( $data, 'test-data-group', 2 );
 
-		$this->assertContains( '<a href="http://wordpress.org">http://wordpress.org</a>', $actual );
-		$this->assertContains( '<a href="https://wordpress.org">https://wordpress.org</a>', $actual );
-		$this->assertContains( 'https://wordpress.org not a link.', $actual );
+		$this->assertStringContainsString( '<a href="http://wordpress.org">http://wordpress.org</a>', $actual );
+		$this->assertStringContainsString( '<a href="https://wordpress.org">https://wordpress.org</a>', $actual );
+		$this->assertStringContainsString( 'https://wordpress.org not a link.', $actual );
 	}
 
 	/**
@@ -137,7 +137,7 @@ class Tests_Privacy_wpPrivacyGeneratePersonalDataExportGroupHtml extends WP_Unit
 
 		$actual = wp_privacy_generate_personal_data_export_group_html( $data, 'escape-html-in-group-labels', 2 );
 
-		$this->assertContains( '<h2 id="escape-html-in-group-labels-escape-html-in-group-labels">&lt;div&gt;Escape HTML in group labels&lt;/div&gt;</h2>', $actual );
+		$this->assertStringContainsString( '<h2 id="escape-html-in-group-labels-escape-html-in-group-labels">&lt;div&gt;Escape HTML in group labels&lt;/div&gt;</h2>', $actual );
 	}
 
 	/**
@@ -163,8 +163,8 @@ class Tests_Privacy_wpPrivacyGeneratePersonalDataExportGroupHtml extends WP_Unit
 		);
 
 		$actual = wp_privacy_generate_personal_data_export_group_html( $data, 'test-data-group', 2 );
-		$this->assertContains( $data['items'][0]['links']['value'], $actual );
-		$this->assertContains( $data['items'][0]['formatting']['value'], $actual );
+		$this->assertStringContainsString( $data['items'][0]['links']['value'], $actual );
+		$this->assertStringContainsString( $data['items'][0]['formatting']['value'], $actual );
 	}
 
 	/**
@@ -191,11 +191,11 @@ class Tests_Privacy_wpPrivacyGeneratePersonalDataExportGroupHtml extends WP_Unit
 
 		$actual = wp_privacy_generate_personal_data_export_group_html( $data, 'test-data-group', 2 );
 
-		$this->assertNotContains( $data['items'][0]['scripts']['value'], $actual );
-		$this->assertContains( '<td>Testing that script tags are stripped.</td>', $actual );
+		$this->assertStringNotContainsString( $data['items'][0]['scripts']['value'], $actual );
+		$this->assertStringContainsString( '<td>Testing that script tags are stripped.</td>', $actual );
 
-		$this->assertNotContains( $data['items'][0]['images']['value'], $actual );
-		$this->assertContains( '<th>Images are not allowed</th><td></td>', $actual );
+		$this->assertStringNotContainsString( $data['items'][0]['images']['value'], $actual );
+		$this->assertStringContainsString( '<th>Images are not allowed</th><td></td>', $actual );
 	}
 
 	/**
@@ -224,8 +224,8 @@ class Tests_Privacy_wpPrivacyGeneratePersonalDataExportGroupHtml extends WP_Unit
 
 		$actual = wp_privacy_generate_personal_data_export_group_html( $data, 'test-data-group', 2 );
 
-		$this->assertContains( '<h2 id="test-data-group-test-data-group">Test Data Group', $actual );
-		$this->assertContains( '<span class="count">(2)</span></h2>', $actual );
+		$this->assertStringContainsString( '<h2 id="test-data-group-test-data-group">Test Data Group', $actual );
+		$this->assertStringContainsString( '<span class="count">(2)</span></h2>', $actual );
 		$this->assertSame( 2, substr_count( $actual, '<table>' ) );
 	}
 
@@ -249,8 +249,8 @@ class Tests_Privacy_wpPrivacyGeneratePersonalDataExportGroupHtml extends WP_Unit
 
 		$actual = wp_privacy_generate_personal_data_export_group_html( $data, 'test-data-group', 2 );
 
-		$this->assertContains( '<h2 id="test-data-group-test-data-group">Test Data Group</h2>', $actual );
-		$this->assertNotContains( '<span class="count">', $actual );
+		$this->assertStringContainsString( '<h2 id="test-data-group-test-data-group">Test Data Group</h2>', $actual );
+		$this->assertStringNotContainsString( '<span class="count">', $actual );
 		$this->assertSame( 1, substr_count( $actual, '<table>' ) );
 	}
 }
diff --git a/tests/phpunit/tests/privacy/wpPrivacySendErasureFulfillmentNotification.php b/tests/phpunit/tests/privacy/wpPrivacySendErasureFulfillmentNotification.php
index 7b865de639..d072588b5e 100644
--- a/tests/phpunit/tests/privacy/wpPrivacySendErasureFulfillmentNotification.php
+++ b/tests/phpunit/tests/privacy/wpPrivacySendErasureFulfillmentNotification.php
@@ -114,14 +114,14 @@ class Tests_Privacy_wpPrivacySendErasureFulfillmentNotification extends WP_UnitT
 		_wp_privacy_send_erasure_fulfillment_notification( self::$request_id );
 
 		$mailer = tests_retrieve_phpmailer_instance();
-		$this->assertContains( self::$requester_email, $mailer->get_recipient( 'to' )->address );
-		$this->assertContains( 'Erasure Request Fulfilled', $mailer->get_sent()->subject );
-		$this->assertContains( 'Your request to erase your personal data', $mailer->get_sent()->body );
-		$this->assertContains( 'has been completed.', $mailer->get_sent()->body );
-		$this->assertContains( wp_specialchars_decode( get_option( 'blogname' ), ENT_QUOTES ), $mailer->get_sent()->body );
-		$this->assertContains( home_url(), $mailer->get_sent()->body );
+		$this->assertStringContainsString( self::$requester_email, $mailer->get_recipient( 'to' )->address );
+		$this->assertStringContainsString( 'Erasure Request Fulfilled', $mailer->get_sent()->subject );
+		$this->assertStringContainsString( 'Your request to erase your personal data', $mailer->get_sent()->body );
+		$this->assertStringContainsString( 'has been completed.', $mailer->get_sent()->body );
+		$this->assertStringContainsString( wp_specialchars_decode( get_option( 'blogname' ), ENT_QUOTES ), $mailer->get_sent()->body );
+		$this->assertStringContainsString( home_url(), $mailer->get_sent()->body );
 
-		$this->assertNotContains( 'you can also read our privacy policy', $mailer->get_sent()->body );
+		$this->assertStringNotContainsString( 'you can also read our privacy policy', $mailer->get_sent()->body );
 		$this->assertTrue( (bool) get_post_meta( self::$request_id, '_wp_user_notified', true ) );
 	}
 
@@ -144,9 +144,9 @@ class Tests_Privacy_wpPrivacySendErasureFulfillmentNotification extends WP_UnitT
 
 		$mailer = tests_retrieve_phpmailer_instance();
 
-		$this->assertContains( self::$requester_email, $mailer->get_recipient( 'to' )->address );
-		$this->assertContains( 'you can also read our privacy policy', $mailer->get_sent()->body );
-		$this->assertContains( get_privacy_policy_url(), $mailer->get_sent()->body );
+		$this->assertStringContainsString( self::$requester_email, $mailer->get_recipient( 'to' )->address );
+		$this->assertStringContainsString( 'you can also read our privacy policy', $mailer->get_sent()->body );
+		$this->assertStringContainsString( get_privacy_policy_url(), $mailer->get_sent()->body );
 		$this->assertTrue( (bool) get_post_meta( self::$request_id, '_wp_user_notified', true ) );
 	}
 
@@ -162,8 +162,8 @@ class Tests_Privacy_wpPrivacySendErasureFulfillmentNotification extends WP_UnitT
 		$mailer = tests_retrieve_phpmailer_instance();
 
 		// Should send an email.
-		$this->assertContains( self::$requester_email, $mailer->get_recipient( 'to' )->address );
-		$this->assertContains( 'Erasure Request Fulfilled', $mailer->get_sent()->subject );
+		$this->assertStringContainsString( self::$requester_email, $mailer->get_recipient( 'to' )->address );
+		$this->assertStringContainsString( 'Erasure Request Fulfilled', $mailer->get_sent()->subject );
 		$this->assertTrue( (bool) get_post_meta( self::$request_id, '_wp_user_notified', true ) );
 
 		reset_phpmailer_instance();
@@ -269,7 +269,7 @@ class Tests_Privacy_wpPrivacySendErasureFulfillmentNotification extends WP_UnitT
 
 		$mailer = tests_retrieve_phpmailer_instance();
 
-		$this->assertContains( 'From: Tester <tester@example.com>', $mailer->get_sent()->header );
+		$this->assertStringContainsString( 'From: Tester <tester@example.com>', $mailer->get_sent()->header );
 	}
 
 	/**
@@ -353,7 +353,7 @@ class Tests_Privacy_wpPrivacySendErasureFulfillmentNotification extends WP_UnitT
 		_wp_privacy_send_erasure_fulfillment_notification( self::$request_id );
 		$mailer = tests_retrieve_phpmailer_instance();
 
-		$this->assertContains( 'Solicitud de borrado completada', $mailer->get_sent()->subject );
+		$this->assertStringContainsString( 'Solicitud de borrado completada', $mailer->get_sent()->subject );
 	}
 
 	/**
@@ -374,7 +374,7 @@ class Tests_Privacy_wpPrivacySendErasureFulfillmentNotification extends WP_UnitT
 		_wp_privacy_send_erasure_fulfillment_notification( self::$request_id );
 		$mailer = tests_retrieve_phpmailer_instance();
 
-		$this->assertContains( 'Löschauftrag ausgeführt', $mailer->get_sent()->subject );
+		$this->assertStringContainsString( 'Löschauftrag ausgeführt', $mailer->get_sent()->subject );
 	}
 
 	/**
@@ -395,7 +395,7 @@ class Tests_Privacy_wpPrivacySendErasureFulfillmentNotification extends WP_UnitT
 		_wp_privacy_send_erasure_fulfillment_notification( self::$request_id );
 		$mailer = tests_retrieve_phpmailer_instance();
 
-		$this->assertContains( 'Solicitud de borrado completada', $mailer->get_sent()->subject );
+		$this->assertStringContainsString( 'Solicitud de borrado completada', $mailer->get_sent()->subject );
 	}
 
 	/**
@@ -418,7 +418,7 @@ class Tests_Privacy_wpPrivacySendErasureFulfillmentNotification extends WP_UnitT
 		_wp_privacy_send_erasure_fulfillment_notification( self::$request_id );
 		$mailer = tests_retrieve_phpmailer_instance();
 
-		$this->assertContains( 'Löschauftrag ausgeführt', $mailer->get_sent()->subject );
+		$this->assertStringContainsString( 'Löschauftrag ausgeführt', $mailer->get_sent()->subject );
 	}
 
 	/**
@@ -444,7 +444,7 @@ class Tests_Privacy_wpPrivacySendErasureFulfillmentNotification extends WP_UnitT
 		_wp_privacy_send_erasure_fulfillment_notification( $request_id );
 		$mailer = tests_retrieve_phpmailer_instance();
 
-		$this->assertContains( 'Erasure Request Fulfilled', $mailer->get_sent()->subject );
+		$this->assertStringContainsString( 'Erasure Request Fulfilled', $mailer->get_sent()->subject );
 	}
 
 	/**
@@ -473,6 +473,6 @@ class Tests_Privacy_wpPrivacySendErasureFulfillmentNotification extends WP_UnitT
 		_wp_privacy_send_erasure_fulfillment_notification( $request_id );
 		$mailer = tests_retrieve_phpmailer_instance();
 
-		$this->assertContains( 'Solicitud de borrado completada', $mailer->get_sent()->subject );
+		$this->assertStringContainsString( 'Solicitud de borrado completada', $mailer->get_sent()->subject );
 	}
 }
diff --git a/tests/phpunit/tests/privacy/wpPrivacySendPersonalDataExportEmail.php b/tests/phpunit/tests/privacy/wpPrivacySendPersonalDataExportEmail.php
index 6fc2b7327f..4a7ab1ca96 100644
--- a/tests/phpunit/tests/privacy/wpPrivacySendPersonalDataExportEmail.php
+++ b/tests/phpunit/tests/privacy/wpPrivacySendPersonalDataExportEmail.php
@@ -114,9 +114,9 @@ class Tests_Privacy_wpPrivacySendPersonalDataExportEmail extends WP_UnitTestCase
 
 		$this->assertSame( 'request-confirmed', get_post_status( self::$request_id ) );
 		$this->assertSame( self::$requester_email, $mailer->get_recipient( 'to' )->address );
-		$this->assertContains( 'Personal Data Export', $mailer->get_sent()->subject );
-		$this->assertContains( $export_file_url, $mailer->get_sent()->body );
-		$this->assertContains( 'please download it', $mailer->get_sent()->body );
+		$this->assertStringContainsString( 'Personal Data Export', $mailer->get_sent()->subject );
+		$this->assertStringContainsString( $export_file_url, $mailer->get_sent()->body );
+		$this->assertStringContainsString( 'please download it', $mailer->get_sent()->body );
 		$this->assertTrue( $email_sent );
 	}
 
@@ -160,7 +160,7 @@ class Tests_Privacy_wpPrivacySendPersonalDataExportEmail extends WP_UnitTestCase
 		wp_privacy_send_personal_data_export_email( self::$request_id );
 
 		$mailer = tests_retrieve_phpmailer_instance();
-		$this->assertContains( 'we will automatically delete the file on December 18, 2017,', $mailer->get_sent()->body );
+		$this->assertStringContainsString( 'we will automatically delete the file on December 18, 2017,', $mailer->get_sent()->body );
 	}
 
 	/**
@@ -238,7 +238,7 @@ class Tests_Privacy_wpPrivacySendPersonalDataExportEmail extends WP_UnitTestCase
 		wp_privacy_send_personal_data_export_email( self::$request_id );
 
 		$mailer = tests_retrieve_phpmailer_instance();
-		$this->assertContains( 'Custom content for request ID: ' . self::$request_id, $mailer->get_sent()->body );
+		$this->assertStringContainsString( 'Custom content for request ID: ' . self::$request_id, $mailer->get_sent()->body );
 	}
 
 	/**
@@ -267,7 +267,7 @@ class Tests_Privacy_wpPrivacySendPersonalDataExportEmail extends WP_UnitTestCase
 
 		$mailer = tests_retrieve_phpmailer_instance();
 
-		$this->assertContains( 'From: Tester <tester@example.com>', $mailer->get_sent()->header );
+		$this->assertStringContainsString( 'From: Tester <tester@example.com>', $mailer->get_sent()->header );
 	}
 
 	/**
@@ -297,7 +297,7 @@ class Tests_Privacy_wpPrivacySendPersonalDataExportEmail extends WP_UnitTestCase
 
 		$site_url = home_url();
 		$mailer   = tests_retrieve_phpmailer_instance();
-		$this->assertContains( 'Custom content using the $site_url of $email_data: ' . $site_url, $mailer->get_sent()->body );
+		$this->assertStringContainsString( 'Custom content using the $site_url of $email_data: ' . $site_url, $mailer->get_sent()->body );
 	}
 
 	/**
@@ -341,7 +341,7 @@ class Tests_Privacy_wpPrivacySendPersonalDataExportEmail extends WP_UnitTestCase
 
 		$mailer = tests_retrieve_phpmailer_instance();
 
-		$this->assertContains( 'Exportación de datos personales', $mailer->get_sent()->subject );
+		$this->assertStringContainsString( 'Exportación de datos personales', $mailer->get_sent()->subject );
 	}
 
 	/**
@@ -363,7 +363,7 @@ class Tests_Privacy_wpPrivacySendPersonalDataExportEmail extends WP_UnitTestCase
 
 		$mailer = tests_retrieve_phpmailer_instance();
 
-		$this->assertContains( 'Export personenbezogener Daten', $mailer->get_sent()->subject );
+		$this->assertStringContainsString( 'Export personenbezogener Daten', $mailer->get_sent()->subject );
 	}
 
 	/**
@@ -385,7 +385,7 @@ class Tests_Privacy_wpPrivacySendPersonalDataExportEmail extends WP_UnitTestCase
 
 		$mailer = tests_retrieve_phpmailer_instance();
 
-		$this->assertContains( 'Exportación de datos personales', $mailer->get_sent()->subject );
+		$this->assertStringContainsString( 'Exportación de datos personales', $mailer->get_sent()->subject );
 	}
 
 	/**
@@ -409,7 +409,7 @@ class Tests_Privacy_wpPrivacySendPersonalDataExportEmail extends WP_UnitTestCase
 
 		$mailer = tests_retrieve_phpmailer_instance();
 
-		$this->assertContains( 'Export personenbezogener Daten', $mailer->get_sent()->subject );
+		$this->assertStringContainsString( 'Export personenbezogener Daten', $mailer->get_sent()->subject );
 	}
 
 	/**
@@ -431,7 +431,7 @@ class Tests_Privacy_wpPrivacySendPersonalDataExportEmail extends WP_UnitTestCase
 
 		$mailer = tests_retrieve_phpmailer_instance();
 
-		$this->assertContains( 'Personal Data Export', $mailer->get_sent()->subject );
+		$this->assertStringContainsString( 'Personal Data Export', $mailer->get_sent()->subject );
 	}
 
 	/**
@@ -456,6 +456,6 @@ class Tests_Privacy_wpPrivacySendPersonalDataExportEmail extends WP_UnitTestCase
 
 		$mailer = tests_retrieve_phpmailer_instance();
 
-		$this->assertContains( 'Exportación de datos personales', $mailer->get_sent()->subject );
+		$this->assertStringContainsString( 'Exportación de datos personales', $mailer->get_sent()->subject );
 	}
 }
diff --git a/tests/phpunit/tests/privacy/wpPrivacySendRequestConfirmationNotification.php b/tests/phpunit/tests/privacy/wpPrivacySendRequestConfirmationNotification.php
index 76c5e39dcb..5f3947e6ac 100644
--- a/tests/phpunit/tests/privacy/wpPrivacySendRequestConfirmationNotification.php
+++ b/tests/phpunit/tests/privacy/wpPrivacySendRequestConfirmationNotification.php
@@ -85,9 +85,9 @@ class Tests_Privacy_wpPrivacySendRequestConfirmationNotification extends WP_Unit
 		$this->assertTrue( (bool) get_post_meta( $request_id, '_wp_user_request_confirmed_timestamp', true ) );
 		$this->assertTrue( (bool) get_post_meta( $request_id, '_wp_admin_notified', true ) );
 		$this->assertSame( get_site_option( 'admin_email' ), $mailer->get_recipient( 'to' )->address );
-		$this->assertContains( 'Action Confirmed', $mailer->get_sent()->subject );
-		$this->assertContains( 'Request: Export Personal Data', $mailer->get_sent()->body );
-		$this->assertContains( 'A user data privacy request has been confirmed', $mailer->get_sent()->body );
+		$this->assertStringContainsString( 'Action Confirmed', $mailer->get_sent()->subject );
+		$this->assertStringContainsString( 'Request: Export Personal Data', $mailer->get_sent()->body );
+		$this->assertStringContainsString( 'A user data privacy request has been confirmed', $mailer->get_sent()->body );
 	}
 
 	/**
@@ -183,7 +183,7 @@ class Tests_Privacy_wpPrivacySendRequestConfirmationNotification extends WP_Unit
 		remove_filter( 'user_request_confirmed_email_content', array( $this, 'modify_email_content' ), 10 );
 
 		$mailer = tests_retrieve_phpmailer_instance();
-		$this->assertContains( 'Custom content containing email address:' . $email, $mailer->get_sent()->body );
+		$this->assertStringContainsString( 'Custom content containing email address:' . $email, $mailer->get_sent()->body );
 	}
 
 	/**
@@ -228,7 +228,7 @@ class Tests_Privacy_wpPrivacySendRequestConfirmationNotification extends WP_Unit
 
 		$mailer = tests_retrieve_phpmailer_instance();
 
-		$this->assertContains( 'From: Tester <tester@example.com>', $mailer->get_sent()->header );
+		$this->assertStringContainsString( 'From: Tester <tester@example.com>', $mailer->get_sent()->header );
 	}
 
 	/**
diff --git a/tests/phpunit/tests/query.php b/tests/phpunit/tests/query.php
index a13783a95d..4784432a8c 100644
--- a/tests/phpunit/tests/query.php
+++ b/tests/phpunit/tests/query.php
@@ -154,7 +154,7 @@ class Tests_Query extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( "ORDER BY $wpdb->posts.post_title DESC, $wpdb->posts.post_date DESC", $q->request );
+		$this->assertStringContainsString( "ORDER BY $wpdb->posts.post_title DESC, $wpdb->posts.post_date DESC", $q->request );
 	}
 
 	public function test_cat_querystring_single_term() {
@@ -571,7 +571,7 @@ class Tests_Query extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( 'LIMIT 0, 5', $q->request );
+		$this->assertStringContainsString( 'LIMIT 0, 5', $q->request );
 	}
 
 	/**
@@ -585,7 +585,7 @@ class Tests_Query extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( 'LIMIT 5, 5', $q->request );
+		$this->assertStringContainsString( 'LIMIT 5, 5', $q->request );
 	}
 
 	/**
@@ -600,7 +600,7 @@ class Tests_Query extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( 'LIMIT 5, 5', $q->request );
+		$this->assertStringContainsString( 'LIMIT 5, 5', $q->request );
 	}
 
 	/**
diff --git a/tests/phpunit/tests/query/dateQuery.php b/tests/phpunit/tests/query/dateQuery.php
index 8b97afd17e..777dec9958 100644
--- a/tests/phpunit/tests/query/dateQuery.php
+++ b/tests/phpunit/tests/query/dateQuery.php
@@ -931,8 +931,8 @@ class Tests_Query_DateQuery extends WP_UnitTestCase {
 
 		$this->assertSame( array( $p1 ), wp_list_pluck( $posts, 'ID' ) );
 
-		$this->assertContains( "MONTH( $wpdb->posts.post_date ) = 5", $this->q->request );
-		$this->assertNotContains( "MONTH( $wpdb->posts.post_date ) = 9", $this->q->request );
+		$this->assertStringContainsString( "MONTH( $wpdb->posts.post_date ) = 5", $this->q->request );
+		$this->assertStringNotContainsString( "MONTH( $wpdb->posts.post_date ) = 9", $this->q->request );
 	}
 
 	public function test_date_params_week_w_duplicate() {
@@ -953,8 +953,8 @@ class Tests_Query_DateQuery extends WP_UnitTestCase {
 
 		$this->assertSame( array( $p2 ), wp_list_pluck( $posts, 'ID' ) );
 
-		$this->assertContains( "WEEK( $wpdb->posts.post_date, 1 ) = 43", $this->q->request );
-		$this->assertNotContains( "WEEK( $wpdb->posts.post_date, 1 ) = 42", $this->q->request );
+		$this->assertStringContainsString( "WEEK( $wpdb->posts.post_date, 1 ) = 43", $this->q->request );
+		$this->assertStringNotContainsString( "WEEK( $wpdb->posts.post_date, 1 ) = 42", $this->q->request );
 	}
 
 	/**
diff --git a/tests/phpunit/tests/query/invalidQueries.php b/tests/phpunit/tests/query/invalidQueries.php
index 9079e30d8b..cce03cdc68 100644
--- a/tests/phpunit/tests/query/invalidQueries.php
+++ b/tests/phpunit/tests/query/invalidQueries.php
@@ -93,8 +93,8 @@ class Tests_Query_InvalidQueries extends WP_UnitTestCase {
 		$query = new WP_Query( array( 'post_type' => 'unregistered_cpt' ) );
 		$posts = $query->get_posts();
 
-		$this->assertContains( "{$wpdb->posts}.post_type = 'unregistered_cpt'", self::$last_posts_request );
-		$this->assertContains( "{$wpdb->posts}.post_status = 'publish'", self::$last_posts_request );
+		$this->assertStringContainsString( "{$wpdb->posts}.post_type = 'unregistered_cpt'", self::$last_posts_request );
+		$this->assertStringContainsString( "{$wpdb->posts}.post_status = 'publish'", self::$last_posts_request );
 		$this->assertCount( 0, $posts );
 	}
 
@@ -113,7 +113,7 @@ class Tests_Query_InvalidQueries extends WP_UnitTestCase {
 		);
 		$posts = $query->get_posts();
 
-		$this->assertContains( "{$wpdb->posts}.post_type = 'unregistered_cpt'", self::$last_posts_request );
+		$this->assertStringContainsString( "{$wpdb->posts}.post_type = 'unregistered_cpt'", self::$last_posts_request );
 		$this->assertCount( 1, $posts, 'the valid `page` post type should still return one post' );
 	}
 
@@ -127,8 +127,8 @@ class Tests_Query_InvalidQueries extends WP_UnitTestCase {
 
 		$this->go_to( home_url( '?post_type=unregistered_cpt' ) );
 
-		$this->assertContains( "{$wpdb->posts}.post_type = 'unregistered_cpt'", self::$last_posts_request );
-		$this->assertContains( "{$wpdb->posts}.post_status = 'publish'", self::$last_posts_request );
+		$this->assertStringContainsString( "{$wpdb->posts}.post_type = 'unregistered_cpt'", self::$last_posts_request );
+		$this->assertStringContainsString( "{$wpdb->posts}.post_status = 'publish'", self::$last_posts_request );
 		// $wp_query recovers to the post type "post" and is expected to return one.
 		$this->assertCount( 1, $wp_query->get_posts() );
 	}
diff --git a/tests/phpunit/tests/query/noFoundRows.php b/tests/phpunit/tests/query/noFoundRows.php
index 7731194d49..457da44994 100644
--- a/tests/phpunit/tests/query/noFoundRows.php
+++ b/tests/phpunit/tests/query/noFoundRows.php
@@ -11,7 +11,7 @@ class Tests_Query_NoFoundRows extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( 'SQL_CALC_FOUND_ROWS', $q->request );
+		$this->assertStringContainsString( 'SQL_CALC_FOUND_ROWS', $q->request );
 	}
 
 	public function test_no_found_rows_false() {
@@ -22,7 +22,7 @@ class Tests_Query_NoFoundRows extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( 'SQL_CALC_FOUND_ROWS', $q->request );
+		$this->assertStringContainsString( 'SQL_CALC_FOUND_ROWS', $q->request );
 	}
 
 	public function test_no_found_rows_0() {
@@ -33,7 +33,7 @@ class Tests_Query_NoFoundRows extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( 'SQL_CALC_FOUND_ROWS', $q->request );
+		$this->assertStringContainsString( 'SQL_CALC_FOUND_ROWS', $q->request );
 	}
 
 	public function test_no_found_rows_empty_string() {
@@ -44,7 +44,7 @@ class Tests_Query_NoFoundRows extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( 'SQL_CALC_FOUND_ROWS', $q->request );
+		$this->assertStringContainsString( 'SQL_CALC_FOUND_ROWS', $q->request );
 	}
 
 	public function test_no_found_rows_true() {
@@ -55,7 +55,7 @@ class Tests_Query_NoFoundRows extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertNotContains( 'SQL_CALC_FOUND_ROWS', $q->request );
+		$this->assertStringNotContainsString( 'SQL_CALC_FOUND_ROWS', $q->request );
 	}
 
 	public function test_no_found_rows_non_bool_cast_to_true() {
@@ -66,7 +66,7 @@ class Tests_Query_NoFoundRows extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertNotContains( 'SQL_CALC_FOUND_ROWS', $q->request );
+		$this->assertStringNotContainsString( 'SQL_CALC_FOUND_ROWS', $q->request );
 	}
 
 	/**
@@ -82,7 +82,7 @@ class Tests_Query_NoFoundRows extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertNotContains( 'SQL_CALC_FOUND_ROWS', $q->request );
+		$this->assertStringNotContainsString( 'SQL_CALC_FOUND_ROWS', $q->request );
 		$this->assertSame( 1, $q->found_posts );
 	}
 
@@ -99,7 +99,7 @@ class Tests_Query_NoFoundRows extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertNotContains( 'SQL_CALC_FOUND_ROWS', $q->request );
+		$this->assertStringNotContainsString( 'SQL_CALC_FOUND_ROWS', $q->request );
 		$this->assertSame( 1, $q->found_posts );
 	}
 }
diff --git a/tests/phpunit/tests/query/postStatus.php b/tests/phpunit/tests/query/postStatus.php
index 19ecc0691b..f8700c0593 100644
--- a/tests/phpunit/tests/query/postStatus.php
+++ b/tests/phpunit/tests/query/postStatus.php
@@ -117,7 +117,7 @@ class Tests_Query_PostStatus extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( "post_status <> 'foo'", $q->request );
+		$this->assertStringContainsString( "post_status <> 'foo'", $q->request );
 	}
 
 	public function test_any_should_include_statuses_where_exclude_from_search_is_false() {
@@ -129,7 +129,7 @@ class Tests_Query_PostStatus extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertNotContains( "post_status <> 'foo'", $q->request );
+		$this->assertStringNotContainsString( "post_status <> 'foo'", $q->request );
 	}
 
 	public function test_private_should_be_included_if_perm_is_false() {
@@ -241,7 +241,7 @@ class Tests_Query_PostStatus extends WP_UnitTestCase {
 		);
 
 		foreach ( get_post_stati( array( 'public' => true ) ) as $status ) {
-			$this->assertContains( "post_status = '$status'", $q->request );
+			$this->assertStringContainsString( "post_status = '$status'", $q->request );
 		}
 	}
 
@@ -254,7 +254,7 @@ class Tests_Query_PostStatus extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertNotContains( "post_status = 'foo", $q->request );
+		$this->assertStringNotContainsString( "post_status = 'foo", $q->request );
 	}
 
 	public function test_protected_should_be_included_when_in_the_admin() {
@@ -273,7 +273,7 @@ class Tests_Query_PostStatus extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( "post_status = 'foo", $q->request );
+		$this->assertStringContainsString( "post_status = 'foo", $q->request );
 	}
 
 	public function test_private_statuses_should_be_included_when_current_user_can_read_private_posts() {
diff --git a/tests/phpunit/tests/query/results.php b/tests/phpunit/tests/query/results.php
index d2ce5dd209..f4a3fe5ebf 100644
--- a/tests/phpunit/tests/query/results.php
+++ b/tests/phpunit/tests/query/results.php
@@ -1049,11 +1049,11 @@ class Tests_Query_Results extends WP_UnitTestCase {
 			)
 		);
 		$this->assertTrue( $this->q->have_posts() );
-		$this->assertContains(
+		$this->assertStringContainsString(
 			"(({$wpdb->posts}.post_status = 'publish') OR ({$wpdb->posts}.post_author = 0 AND ({$wpdb->posts}.post_status = 'private')))",
 			$this->q->request
 		);
-		$this->assertNotContains( "({$wpdb->posts}.post_status = 'publish') AND", $this->q->request );
+		$this->assertStringNotContainsString( "({$wpdb->posts}.post_status = 'publish') AND", $this->q->request );
 	}
 
 	/**
@@ -1202,7 +1202,7 @@ class Tests_Query_Results extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( 'contributing-to-the-wordpress-codex/getting-started', get_permalink( $post_2 ) );
+		$this->assertStringContainsString( 'contributing-to-the-wordpress-codex/getting-started', get_permalink( $post_2 ) );
 
 		$result = $this->q->query(
 			array(
diff --git a/tests/phpunit/tests/query/search.php b/tests/phpunit/tests/query/search.php
index b70bdc6d44..2f54f18724 100644
--- a/tests/phpunit/tests/query/search.php
+++ b/tests/phpunit/tests/query/search.php
@@ -309,7 +309,7 @@ class Tests_Query_Search extends WP_UnitTestCase {
 		remove_filter( 'posts_search', array( $this, 'filter_posts_search' ) );
 		remove_filter( 'posts_search_orderby', array( $this, 'filter_posts_search' ) );
 
-		$this->assertNotContains( 'posts_search', $q->request );
+		$this->assertStringNotContainsString( 'posts_search', $q->request );
 	}
 
 	/**
diff --git a/tests/phpunit/tests/rest-api/rest-attachments-controller.php b/tests/phpunit/tests/rest-api/rest-attachments-controller.php
index a2f7087528..006e9f7834 100644
--- a/tests/phpunit/tests/rest-api/rest-attachments-controller.php
+++ b/tests/phpunit/tests/rest-api/rest-attachments-controller.php
@@ -976,7 +976,7 @@ class WP_Test_REST_Attachments_Controller extends WP_Test_REST_Post_Type_Control
 		$request->set_body( file_get_contents( $this->test_file ) );
 		$response   = rest_get_server()->dispatch( $request );
 		$attachment = $response->get_data();
-		$this->assertNotContains( ABSPATH, get_post_meta( $attachment['id'], '_wp_attached_file', true ) );
+		$this->assertStringNotContainsString( ABSPATH, get_post_meta( $attachment['id'], '_wp_attached_file', true ) );
 	}
 
 	public function test_update_item() {
@@ -2102,7 +2102,7 @@ class WP_Test_REST_Attachments_Controller extends WP_Test_REST_Post_Type_Control
 		$this->assertStringEndsWith( '-edited.jpg', $item['media_details']['file'] );
 		$this->assertArrayHasKey( 'parent_image', $item['media_details'] );
 		$this->assertEquals( $attachment, $item['media_details']['parent_image']['attachment_id'] );
-		$this->assertContains( 'canola', $item['media_details']['parent_image']['file'] );
+		$this->assertStringContainsString( 'canola', $item['media_details']['parent_image']['file'] );
 	}
 
 	/**
@@ -2145,7 +2145,7 @@ class WP_Test_REST_Attachments_Controller extends WP_Test_REST_Post_Type_Control
 		$this->assertStringEndsWith( '-edited.jpg', $item['media_details']['file'] );
 		$this->assertArrayHasKey( 'parent_image', $item['media_details'] );
 		$this->assertEquals( $attachment, $item['media_details']['parent_image']['attachment_id'] );
-		$this->assertContains( 'canola', $item['media_details']['parent_image']['file'] );
+		$this->assertStringContainsString( 'canola', $item['media_details']['parent_image']['file'] );
 	}
 
 	/**
diff --git a/tests/phpunit/tests/rest-api/rest-block-renderer-controller.php b/tests/phpunit/tests/rest-api/rest-block-renderer-controller.php
index fb21cfa2a6..50d9cf79eb 100644
--- a/tests/phpunit/tests/rest-api/rest-block-renderer-controller.php
+++ b/tests/phpunit/tests/rest-api/rest-block-renderer-controller.php
@@ -506,7 +506,7 @@ class REST_Block_Renderer_Controller_Test extends WP_Test_REST_Controller_Testca
 		$response = rest_get_server()->dispatch( $request );
 
 		$this->assertSame( 200, $response->get_status() );
-		$this->assertContains( $string_attribute, $response->get_data()['rendered'] );
+		$this->assertStringContainsString( $string_attribute, $response->get_data()['rendered'] );
 	}
 
 	/**
diff --git a/tests/phpunit/tests/rest-api/rest-categories-controller.php b/tests/phpunit/tests/rest-api/rest-categories-controller.php
index ddfcaf87f1..c5a2cf14c7 100644
--- a/tests/phpunit/tests/rest-api/rest-categories-controller.php
+++ b/tests/phpunit/tests/rest-api/rest-categories-controller.php
@@ -278,7 +278,7 @@ class WP_Test_REST_Categories_Controller extends WP_Test_REST_Controller_Testcas
 		$this->assertErrorResponse( 'rest_invalid_param', $response, 400 );
 		$data        = $response->get_data();
 		$first_error = array_shift( $data['data']['params'] );
-		$this->assertContains( 'page must be greater than or equal to 1', $first_error );
+		$this->assertStringContainsString( 'page must be greater than or equal to 1', $first_error );
 	}
 
 	public function test_get_items_include_query() {
@@ -627,7 +627,7 @@ class WP_Test_REST_Categories_Controller extends WP_Test_REST_Controller_Testcas
 			rest_url( 'wp/v2/categories' )
 		);
 		$this->assertStringNotContainsString( 'rel="prev"', $headers['Link'] );
-		$this->assertContains( '<' . $next_link . '>; rel="next"', $headers['Link'] );
+		$this->assertStringContainsString( '<' . $next_link . '>; rel="next"', $headers['Link'] );
 
 		// 3rd page.
 		$this->factory->category->create();
@@ -646,14 +646,14 @@ class WP_Test_REST_Categories_Controller extends WP_Test_REST_Controller_Testcas
 			),
 			rest_url( 'wp/v2/categories' )
 		);
-		$this->assertContains( '<' . $prev_link . '>; rel="prev"', $headers['Link'] );
+		$this->assertStringContainsString( '<' . $prev_link . '>; rel="prev"', $headers['Link'] );
 		$next_link = add_query_arg(
 			array(
 				'page' => 4,
 			),
 			rest_url( 'wp/v2/categories' )
 		);
-		$this->assertContains( '<' . $next_link . '>; rel="next"', $headers['Link'] );
+		$this->assertStringContainsString( '<' . $next_link . '>; rel="next"', $headers['Link'] );
 
 		// Last page.
 		$request = new WP_REST_Request( 'GET', '/wp/v2/categories' );
@@ -669,7 +669,7 @@ class WP_Test_REST_Categories_Controller extends WP_Test_REST_Controller_Testcas
 			),
 			rest_url( 'wp/v2/categories' )
 		);
-		$this->assertContains( '<' . $prev_link . '>; rel="prev"', $headers['Link'] );
+		$this->assertStringContainsString( '<' . $prev_link . '>; rel="prev"', $headers['Link'] );
 		$this->assertStringNotContainsString( 'rel="next"', $headers['Link'] );
 
 		// Out of bounds.
@@ -686,7 +686,7 @@ class WP_Test_REST_Categories_Controller extends WP_Test_REST_Controller_Testcas
 			),
 			rest_url( 'wp/v2/categories' )
 		);
-		$this->assertContains( '<' . $prev_link . '>; rel="prev"', $headers['Link'] );
+		$this->assertStringContainsString( '<' . $prev_link . '>; rel="prev"', $headers['Link'] );
 		$this->assertStringNotContainsString( 'rel="next"', $headers['Link'] );
 	}
 
@@ -810,7 +810,7 @@ class WP_Test_REST_Categories_Controller extends WP_Test_REST_Controller_Testcas
 		$this->assertSame( 201, $response->get_status() );
 		$headers = $response->get_headers();
 		$data    = $response->get_data();
-		$this->assertContains( '/wp/v2/categories/' . $data['id'], $headers['Location'] );
+		$this->assertStringContainsString( '/wp/v2/categories/' . $data['id'], $headers['Location'] );
 		$this->assertSame( 'My Awesome Term', $data['name'] );
 		$this->assertSame( 'This term is so awesome.', $data['description'] );
 		$this->assertSame( 'so-awesome', $data['slug'] );
@@ -1224,7 +1224,7 @@ class WP_Test_REST_Categories_Controller extends WP_Test_REST_Controller_Testcas
 		}
 
 		$this->assertSameSets( $relations, array_keys( $links ) );
-		$this->assertContains( 'wp/v2/taxonomies/' . $term->taxonomy, $links['about'][0]['href'] );
+		$this->assertStringContainsString( 'wp/v2/taxonomies/' . $term->taxonomy, $links['about'][0]['href'] );
 		$this->assertSame( add_query_arg( 'categories', $term->term_id, rest_url( 'wp/v2/posts' ) ), $links['https://api.w.org/post_type'][0]['href'] );
 	}
 
diff --git a/tests/phpunit/tests/rest-api/rest-comments-controller.php b/tests/phpunit/tests/rest-api/rest-comments-controller.php
index a1e8c03fb7..7cd9203db8 100644
--- a/tests/phpunit/tests/rest-api/rest-comments-controller.php
+++ b/tests/phpunit/tests/rest-api/rest-comments-controller.php
@@ -822,7 +822,7 @@ class WP_Test_REST_Comments_Controller extends WP_Test_REST_Controller_Testcase
 			rest_url( '/wp/v2/comments' )
 		);
 		$this->assertStringNotContainsString( 'rel="prev"', $headers['Link'] );
-		$this->assertContains( '<' . $next_link . '>; rel="next"', $headers['Link'] );
+		$this->assertStringContainsString( '<' . $next_link . '>; rel="next"', $headers['Link'] );
 
 		// 3rd page.
 		$this->factory->comment->create(
@@ -844,14 +844,14 @@ class WP_Test_REST_Comments_Controller extends WP_Test_REST_Controller_Testcase
 			),
 			rest_url( '/wp/v2/comments' )
 		);
-		$this->assertContains( '<' . $prev_link . '>; rel="prev"', $headers['Link'] );
+		$this->assertStringContainsString( '<' . $prev_link . '>; rel="prev"', $headers['Link'] );
 		$next_link = add_query_arg(
 			array(
 				'page' => 4,
 			),
 			rest_url( '/wp/v2/comments' )
 		);
-		$this->assertContains( '<' . $next_link . '>; rel="next"', $headers['Link'] );
+		$this->assertStringContainsString( '<' . $next_link . '>; rel="next"', $headers['Link'] );
 
 		// Last page.
 		$request = new WP_REST_Request( 'GET', '/wp/v2/comments' );
@@ -866,7 +866,7 @@ class WP_Test_REST_Comments_Controller extends WP_Test_REST_Controller_Testcase
 			),
 			rest_url( '/wp/v2/comments' )
 		);
-		$this->assertContains( '<' . $prev_link . '>; rel="prev"', $headers['Link'] );
+		$this->assertStringContainsString( '<' . $prev_link . '>; rel="prev"', $headers['Link'] );
 		$this->assertStringNotContainsString( 'rel="next"', $headers['Link'] );
 
 		// Out of bounds.
@@ -882,7 +882,7 @@ class WP_Test_REST_Comments_Controller extends WP_Test_REST_Controller_Testcase
 			),
 			rest_url( '/wp/v2/comments' )
 		);
-		$this->assertContains( '<' . $prev_link . '>; rel="prev"', $headers['Link'] );
+		$this->assertStringContainsString( '<' . $prev_link . '>; rel="prev"', $headers['Link'] );
 		$this->assertStringNotContainsString( 'rel="next"', $headers['Link'] );
 	}
 
diff --git a/tests/phpunit/tests/rest-api/rest-pages-controller.php b/tests/phpunit/tests/rest-api/rest-pages-controller.php
index 411b39061f..aefc0452f2 100644
--- a/tests/phpunit/tests/rest-api/rest-pages-controller.php
+++ b/tests/phpunit/tests/rest-api/rest-pages-controller.php
@@ -290,13 +290,13 @@ class WP_Test_REST_Pages_Controller extends WP_Test_REST_Post_Type_Controller_Te
 		$data = $response->get_data();
 		// Safe format for 4.4 and 4.5. See https://core.trac.wordpress.org/ticket/35028
 		$first_error = array_shift( $data['data']['params'] );
-		$this->assertContains( 'per_page must be between 1 (inclusive) and 100 (inclusive)', $first_error );
+		$this->assertStringContainsString( 'per_page must be between 1 (inclusive) and 100 (inclusive)', $first_error );
 		$request->set_param( 'per_page', 101 );
 		$response = rest_get_server()->dispatch( $request );
 		$this->assertErrorResponse( 'rest_invalid_param', $response, 400 );
 		$data        = $response->get_data();
 		$first_error = array_shift( $data['data']['params'] );
-		$this->assertContains( 'per_page must be between 1 (inclusive) and 100 (inclusive)', $first_error );
+		$this->assertStringContainsString( 'per_page must be between 1 (inclusive) and 100 (inclusive)', $first_error );
 	}
 
 	public function test_get_items_private_filter_query_var() {
diff --git a/tests/phpunit/tests/rest-api/rest-posts-controller.php b/tests/phpunit/tests/rest-api/rest-posts-controller.php
index b3a2f2869b..f330fefe2c 100644
--- a/tests/phpunit/tests/rest-api/rest-posts-controller.php
+++ b/tests/phpunit/tests/rest-api/rest-posts-controller.php
@@ -1532,7 +1532,7 @@ class WP_Test_REST_Posts_Controller extends WP_Test_REST_Post_Type_Controller_Te
 			rest_url( '/wp/v2/posts' )
 		);
 		$this->assertStringNotContainsString( 'rel="prev"', $headers['Link'] );
-		$this->assertContains( '<' . $next_link . '>; rel="next"', $headers['Link'] );
+		$this->assertStringContainsString( '<' . $next_link . '>; rel="next"', $headers['Link'] );
 
 		// 3rd page.
 		$this->factory->post->create();
@@ -1550,14 +1550,14 @@ class WP_Test_REST_Posts_Controller extends WP_Test_REST_Post_Type_Controller_Te
 			),
 			rest_url( '/wp/v2/posts' )
 		);
-		$this->assertContains( '<' . $prev_link . '>; rel="prev"', $headers['Link'] );
+		$this->assertStringContainsString( '<' . $prev_link . '>; rel="prev"', $headers['Link'] );
 		$next_link = add_query_arg(
 			array(
 				'page' => 4,
 			),
 			rest_url( '/wp/v2/posts' )
 		);
-		$this->assertContains( '<' . $next_link . '>; rel="next"', $headers['Link'] );
+		$this->assertStringContainsString( '<' . $next_link . '>; rel="next"', $headers['Link'] );
 
 		// Last page.
 		$request = new WP_REST_Request( 'GET', '/wp/v2/posts' );
@@ -1572,7 +1572,7 @@ class WP_Test_REST_Posts_Controller extends WP_Test_REST_Post_Type_Controller_Te
 			),
 			rest_url( '/wp/v2/posts' )
 		);
-		$this->assertContains( '<' . $prev_link . '>; rel="prev"', $headers['Link'] );
+		$this->assertStringContainsString( '<' . $prev_link . '>; rel="prev"', $headers['Link'] );
 		$this->assertStringNotContainsString( 'rel="next"', $headers['Link'] );
 
 		// Out of bounds.
@@ -1602,7 +1602,7 @@ class WP_Test_REST_Posts_Controller extends WP_Test_REST_Post_Type_Controller_Te
 			),
 			rest_url( '/wp/v2/posts' )
 		);
-		$this->assertContains( '<' . $prev_link . '>; rel="prev"', $headers['Link'] );
+		$this->assertStringContainsString( '<' . $prev_link . '>; rel="prev"', $headers['Link'] );
 		$next_link = add_query_arg(
 			array(
 				'per_page' => 5,
@@ -1610,7 +1610,7 @@ class WP_Test_REST_Posts_Controller extends WP_Test_REST_Post_Type_Controller_Te
 			),
 			rest_url( '/wp/v2/posts' )
 		);
-		$this->assertContains( '<' . $next_link . '>; rel="next"', $headers['Link'] );
+		$this->assertStringContainsString( '<' . $next_link . '>; rel="next"', $headers['Link'] );
 	}
 
 	public function test_get_items_status_draft_permissions() {
@@ -1884,7 +1884,7 @@ class WP_Test_REST_Posts_Controller extends WP_Test_REST_Post_Type_Controller_Te
 		$request->set_param( 'context', 'edit' );
 		$response = rest_get_server()->dispatch( $request );
 		$data     = $response->get_data();
-		$this->assertNotContains( $post_content, $data['content']['rendered'] );
+		$this->assertStringNotContainsString( $post_content, $data['content']['rendered'] );
 	}
 
 	public function test_get_post_invalid_id() {
diff --git a/tests/phpunit/tests/rest-api/rest-revisions-controller.php b/tests/phpunit/tests/rest-api/rest-revisions-controller.php
index 1121b883af..da36adae1c 100644
--- a/tests/phpunit/tests/rest-api/rest-revisions-controller.php
+++ b/tests/phpunit/tests/rest-api/rest-revisions-controller.php
@@ -483,7 +483,7 @@ class WP_Test_REST_Revisions_Controller extends WP_Test_REST_Controller_Testcase
 			rest_url( $rest_route )
 		);
 		$this->assertStringNotContainsString( 'rel="prev"', $headers['Link'] );
-		$this->assertContains( '<' . $next_link . '>; rel="next"', $headers['Link'] );
+		$this->assertStringContainsString( '<' . $next_link . '>; rel="next"', $headers['Link'] );
 	}
 
 	/**
@@ -517,7 +517,7 @@ class WP_Test_REST_Revisions_Controller extends WP_Test_REST_Controller_Testcase
 			),
 			rest_url( $rest_route )
 		);
-		$this->assertContains( '<' . $prev_link . '>; rel="prev"', $headers['Link'] );
+		$this->assertStringContainsString( '<' . $prev_link . '>; rel="prev"', $headers['Link'] );
 	}
 
 	/**
@@ -604,7 +604,7 @@ class WP_Test_REST_Revisions_Controller extends WP_Test_REST_Controller_Testcase
 		$response = rest_get_server()->dispatch( $request );
 		$data     = $response->get_data();
 		$this->assertCount( $expected_count, $data );
-		$this->assertContains( $expected_content, $data[0]['content']['rendered'] );
+		$this->assertStringContainsString( $expected_content, $data[0]['content']['rendered'] );
 	}
 
 	/**
diff --git a/tests/phpunit/tests/rest-api/rest-tags-controller.php b/tests/phpunit/tests/rest-api/rest-tags-controller.php
index d117f7fa4b..143ef50a7c 100644
--- a/tests/phpunit/tests/rest-api/rest-tags-controller.php
+++ b/tests/phpunit/tests/rest-api/rest-tags-controller.php
@@ -591,7 +591,7 @@ class WP_Test_REST_Tags_Controller extends WP_Test_REST_Controller_Testcase {
 			rest_url( 'wp/v2/tags' )
 		);
 		$this->assertStringNotContainsString( 'rel="prev"', $headers['Link'] );
-		$this->assertContains( '<' . $next_link . '>; rel="next"', $headers['Link'] );
+		$this->assertStringContainsString( '<' . $next_link . '>; rel="next"', $headers['Link'] );
 
 		// 3rd page.
 		$this->factory->tag->create();
@@ -609,14 +609,14 @@ class WP_Test_REST_Tags_Controller extends WP_Test_REST_Controller_Testcase {
 			),
 			rest_url( 'wp/v2/tags' )
 		);
-		$this->assertContains( '<' . $prev_link . '>; rel="prev"', $headers['Link'] );
+		$this->assertStringContainsString( '<' . $prev_link . '>; rel="prev"', $headers['Link'] );
 		$next_link = add_query_arg(
 			array(
 				'page' => 4,
 			),
 			rest_url( 'wp/v2/tags' )
 		);
-		$this->assertContains( '<' . $next_link . '>; rel="next"', $headers['Link'] );
+		$this->assertStringContainsString( '<' . $next_link . '>; rel="next"', $headers['Link'] );
 
 		// Last page.
 		$request = new WP_REST_Request( 'GET', '/wp/v2/tags' );
@@ -631,7 +631,7 @@ class WP_Test_REST_Tags_Controller extends WP_Test_REST_Controller_Testcase {
 			),
 			rest_url( 'wp/v2/tags' )
 		);
-		$this->assertContains( '<' . $prev_link . '>; rel="prev"', $headers['Link'] );
+		$this->assertStringContainsString( '<' . $prev_link . '>; rel="prev"', $headers['Link'] );
 		$this->assertStringNotContainsString( 'rel="next"', $headers['Link'] );
 
 		// Out of bounds.
@@ -647,7 +647,7 @@ class WP_Test_REST_Tags_Controller extends WP_Test_REST_Controller_Testcase {
 			),
 			rest_url( 'wp/v2/tags' )
 		);
-		$this->assertContains( '<' . $prev_link . '>; rel="prev"', $headers['Link'] );
+		$this->assertStringContainsString( '<' . $prev_link . '>; rel="prev"', $headers['Link'] );
 		$this->assertStringNotContainsString( 'rel="next"', $headers['Link'] );
 	}
 
@@ -759,7 +759,7 @@ class WP_Test_REST_Tags_Controller extends WP_Test_REST_Controller_Testcase {
 		$this->assertSame( 201, $response->get_status() );
 		$headers = $response->get_headers();
 		$data    = $response->get_data();
-		$this->assertContains( '/wp/v2/tags/' . $data['id'], $headers['Location'] );
+		$this->assertStringContainsString( '/wp/v2/tags/' . $data['id'], $headers['Location'] );
 		$this->assertSame( 'My Awesome Term', $data['name'] );
 		$this->assertSame( 'This term is so awesome.', $data['description'] );
 		$this->assertSame( 'so-awesome', $data['slug'] );
@@ -776,7 +776,7 @@ class WP_Test_REST_Tags_Controller extends WP_Test_REST_Controller_Testcase {
 		$this->assertSame( 201, $response->get_status() );
 		$headers = $response->get_headers();
 		$data    = $response->get_data();
-		$this->assertContains( '/wp/v2/tags/' . $data['id'], $headers['Location'] );
+		$this->assertStringContainsString( '/wp/v2/tags/' . $data['id'], $headers['Location'] );
 		$this->assertSame( 'My Awesome Term', $data['name'] );
 		$this->assertSame( 'This term is so awesome.', $data['description'] );
 		$this->assertSame( 'so-awesome', $data['slug'] );
@@ -819,7 +819,7 @@ class WP_Test_REST_Tags_Controller extends WP_Test_REST_Controller_Testcase {
 		$this->assertSame( 201, $response->get_status() );
 		$headers = $response->get_headers();
 		$data    = $response->get_data();
-		$this->assertContains( '/wp/v2/tags/' . $data['id'], $headers['Location'] );
+		$this->assertStringContainsString( '/wp/v2/tags/' . $data['id'], $headers['Location'] );
 		$this->assertSame( 'My Awesome Term', $data['name'] );
 		$this->assertSame( 'hello', get_term_meta( $data['id'], 'test_tag_single', true ) );
 	}
@@ -837,7 +837,7 @@ class WP_Test_REST_Tags_Controller extends WP_Test_REST_Controller_Testcase {
 		$this->assertSame( 201, $response->get_status() );
 		$headers = $response->get_headers();
 		$data    = $response->get_data();
-		$this->assertContains( '/wp/v2/tags/' . $data['id'], $headers['Location'] );
+		$this->assertStringContainsString( '/wp/v2/tags/' . $data['id'], $headers['Location'] );
 		$this->assertSame( 'My Awesome Term', $data['name'] );
 		$this->assertSame( '', get_term_meta( $existing_tag_id, 'test_tag_single', true ) );
 		$this->assertSame( 'hello', get_term_meta( $data['id'], 'test_tag_single', true ) );
@@ -1439,7 +1439,7 @@ class WP_Test_REST_Tags_Controller extends WP_Test_REST_Controller_Testcase {
 			$expected_links[] = 'up';
 		}
 		$this->assertSameSets( $expected_links, array_keys( $links ) );
-		$this->assertContains( 'wp/v2/taxonomies/' . $term->taxonomy, $links['about'][0]['href'] );
+		$this->assertStringContainsString( 'wp/v2/taxonomies/' . $term->taxonomy, $links['about'][0]['href'] );
 		$this->assertSame( add_query_arg( 'tags', $term->term_id, rest_url( 'wp/v2/posts' ) ), $links['https://api.w.org/post_type'][0]['href'] );
 	}
 
diff --git a/tests/phpunit/tests/rest-api/rest-users-controller.php b/tests/phpunit/tests/rest-api/rest-users-controller.php
index 751465a5c1..4d06f99a15 100644
--- a/tests/phpunit/tests/rest-api/rest-users-controller.php
+++ b/tests/phpunit/tests/rest-api/rest-users-controller.php
@@ -322,7 +322,7 @@ class WP_Test_REST_Users_Controller extends WP_Test_REST_Controller_Testcase {
 			rest_url( 'wp/v2/users' )
 		);
 		$this->assertStringNotContainsString( 'rel="prev"', $headers['Link'] );
-		$this->assertContains( '<' . $next_link . '>; rel="next"', $headers['Link'] );
+		$this->assertStringContainsString( '<' . $next_link . '>; rel="next"', $headers['Link'] );
 
 		// 3rd page.
 		$this->factory->user->create();
@@ -340,14 +340,14 @@ class WP_Test_REST_Users_Controller extends WP_Test_REST_Controller_Testcase {
 			),
 			rest_url( 'wp/v2/users' )
 		);
-		$this->assertContains( '<' . $prev_link . '>; rel="prev"', $headers['Link'] );
+		$this->assertStringContainsString( '<' . $prev_link . '>; rel="prev"', $headers['Link'] );
 		$next_link = add_query_arg(
 			array(
 				'page' => 4,
 			),
 			rest_url( 'wp/v2/users' )
 		);
-		$this->assertContains( '<' . $next_link . '>; rel="next"', $headers['Link'] );
+		$this->assertStringContainsString( '<' . $next_link . '>; rel="next"', $headers['Link'] );
 
 		// Last page.
 		$request = new WP_REST_Request( 'GET', '/wp/v2/users' );
@@ -362,7 +362,7 @@ class WP_Test_REST_Users_Controller extends WP_Test_REST_Controller_Testcase {
 			),
 			rest_url( 'wp/v2/users' )
 		);
-		$this->assertContains( '<' . $prev_link . '>; rel="prev"', $headers['Link'] );
+		$this->assertStringContainsString( '<' . $prev_link . '>; rel="prev"', $headers['Link'] );
 		$this->assertStringNotContainsString( 'rel="next"', $headers['Link'] );
 
 		// Out of bounds.
@@ -378,7 +378,7 @@ class WP_Test_REST_Users_Controller extends WP_Test_REST_Controller_Testcase {
 			),
 			rest_url( 'wp/v2/users' )
 		);
-		$this->assertContains( '<' . $prev_link . '>; rel="prev"', $headers['Link'] );
+		$this->assertStringContainsString( '<' . $prev_link . '>; rel="prev"', $headers['Link'] );
 		$this->assertStringNotContainsString( 'rel="next"', $headers['Link'] );
 	}
 
@@ -411,7 +411,7 @@ class WP_Test_REST_Users_Controller extends WP_Test_REST_Controller_Testcase {
 			rest_url( 'wp/v2/users' )
 		);
 		$headers   = $response->get_headers();
-		$this->assertContains( '<' . $prev_link . '>; rel="prev"', $headers['Link'] );
+		$this->assertStringContainsString( '<' . $prev_link . '>; rel="prev"', $headers['Link'] );
 	}
 
 	public function test_get_items_orderby_name() {
diff --git a/tests/phpunit/tests/rewrite.php b/tests/phpunit/tests/rewrite.php
index a6b99ab4b9..11b55a850a 100644
--- a/tests/phpunit/tests/rewrite.php
+++ b/tests/phpunit/tests/rewrite.php
@@ -82,7 +82,7 @@ class Tests_Rewrite extends WP_UnitTestCase {
 
 		$extra_rules_top = $wp_rewrite->extra_rules_top;
 
-		$this->assertContains( $redirect, $extra_rules_top[ $pattern ] );
+		$this->assertStringContainsString( $redirect, $extra_rules_top[ $pattern ] );
 	}
 
 	function test_url_to_postid() {
diff --git a/tests/phpunit/tests/robots.php b/tests/phpunit/tests/robots.php
index 49fbccfe96..bf715e8568 100644
--- a/tests/phpunit/tests/robots.php
+++ b/tests/phpunit/tests/robots.php
@@ -68,7 +68,7 @@ class Tests_Robots extends WP_UnitTestCase {
 		);
 
 		$output = get_echo( 'wp_robots' );
-		$this->assertContains( "'{$expected_directives_string}'", $output );
+		$this->assertStringContainsString( "'{$expected_directives_string}'", $output );
 	}
 
 	/**
@@ -83,7 +83,7 @@ class Tests_Robots extends WP_UnitTestCase {
 
 		update_option( 'blog_public', '0' );
 		$output = get_echo( 'wp_robots' );
-		$this->assertContains( "'noindex, nofollow'", $output );
+		$this->assertStringContainsString( "'noindex, nofollow'", $output );
 	}
 
 	/**
@@ -94,11 +94,11 @@ class Tests_Robots extends WP_UnitTestCase {
 
 		update_option( 'blog_public', '1' );
 		$output = get_echo( 'wp_robots' );
-		$this->assertContains( "'noindex, follow'", $output );
+		$this->assertStringContainsString( "'noindex, follow'", $output );
 
 		update_option( 'blog_public', '0' );
 		$output = get_echo( 'wp_robots' );
-		$this->assertContains( "'noindex, nofollow'", $output );
+		$this->assertStringContainsString( "'noindex, nofollow'", $output );
 	}
 
 	/**
@@ -108,7 +108,7 @@ class Tests_Robots extends WP_UnitTestCase {
 		add_filter( 'wp_robots', 'wp_robots_sensitive_page' );
 
 		$output = get_echo( 'wp_robots' );
-		$this->assertContains( "'noindex, noarchive'", $output );
+		$this->assertStringContainsString( "'noindex, noarchive'", $output );
 	}
 
 	/**
@@ -119,7 +119,7 @@ class Tests_Robots extends WP_UnitTestCase {
 
 		update_option( 'blog_public', '1' );
 		$output = get_echo( 'wp_robots' );
-		$this->assertContains( "'max-image-preview:large'", $output );
+		$this->assertStringContainsString( "'max-image-preview:large'", $output );
 
 		update_option( 'blog_public', '0' );
 		$output = get_echo( 'wp_robots' );
@@ -134,7 +134,7 @@ class Tests_Robots extends WP_UnitTestCase {
 		$this->go_to( home_url( '?s=ticket+52457+core.trac.wordpress.org' ) );
 
 		$output = get_echo( 'wp_robots' );
-		$this->assertContains( 'noindex', $output );
+		$this->assertStringContainsString( 'noindex', $output );
 	}
 
 	/**
@@ -145,7 +145,7 @@ class Tests_Robots extends WP_UnitTestCase {
 		$this->go_to( home_url() );
 
 		$output = get_echo( 'wp_robots' );
-		$this->assertNotContains( 'noindex', $output );
+		$this->assertStringNotContainsString( 'noindex', $output );
 	}
 
 	public function add_noindex_directive( array $robots ) {
diff --git a/tests/phpunit/tests/sitemaps/sitemaps.php b/tests/phpunit/tests/sitemaps/sitemaps.php
index da47954e8e..6cbe77b008 100644
--- a/tests/phpunit/tests/sitemaps/sitemaps.php
+++ b/tests/phpunit/tests/sitemaps/sitemaps.php
@@ -404,7 +404,7 @@ class Test_Sitemaps extends WP_UnitTestCase {
 		$robots_text    = apply_filters( 'robots_txt', '', true );
 		$sitemap_string = 'Sitemap: http://' . WP_TESTS_DOMAIN . '/?sitemap=index';
 
-		$this->assertContains( $sitemap_string, $robots_text, 'Sitemap URL not included in robots text.' );
+		$this->assertStringContainsString( $sitemap_string, $robots_text, 'Sitemap URL not included in robots text.' );
 	}
 
 	/**
@@ -414,7 +414,7 @@ class Test_Sitemaps extends WP_UnitTestCase {
 		$robots_text    = apply_filters( 'robots_txt', '', false );
 		$sitemap_string = 'Sitemap: http://' . WP_TESTS_DOMAIN . '/?sitemap=index';
 
-		$this->assertNotContains( $sitemap_string, $robots_text );
+		$this->assertStringNotContainsString( $sitemap_string, $robots_text );
 	}
 
 	/**
@@ -431,7 +431,7 @@ class Test_Sitemaps extends WP_UnitTestCase {
 		// Clean up permalinks.
 		$this->set_permalink_structure();
 
-		$this->assertContains( $sitemap_string, $robots_text, 'Sitemap URL not included in robots text.' );
+		$this->assertStringContainsString( $sitemap_string, $robots_text, 'Sitemap URL not included in robots text.' );
 	}
 
 	/**
@@ -442,7 +442,7 @@ class Test_Sitemaps extends WP_UnitTestCase {
 		$robots_text    = apply_filters( 'robots_txt', '', true );
 		$sitemap_string = "\nSitemap: ";
 
-		$this->assertContains( $sitemap_string, $robots_text, 'Sitemap URL not prefixed with "\n".' );
+		$this->assertStringContainsString( $sitemap_string, $robots_text, 'Sitemap URL not prefixed with "\n".' );
 	}
 
 	/**
diff --git a/tests/phpunit/tests/term/getTermBy.php b/tests/phpunit/tests/term/getTermBy.php
index ab49ea92ef..b0399cbf1b 100644
--- a/tests/phpunit/tests/term/getTermBy.php
+++ b/tests/phpunit/tests/term/getTermBy.php
@@ -202,7 +202,7 @@ class Tests_Term_GetTermBy extends WP_UnitTestCase {
 		);
 		$found   = get_term_by( 'name', 'burrito', 'post_tag' );
 		$this->assertSame( $term_id, $found->term_id );
-		$this->assertNotContains( 'ORDER BY', $wpdb->last_query );
+		$this->assertStringNotContainsString( 'ORDER BY', $wpdb->last_query );
 	}
 
 	/**
@@ -219,7 +219,7 @@ class Tests_Term_GetTermBy extends WP_UnitTestCase {
 		);
 		$found   = get_term_by( 'name', 'burrito', 'post_tag' );
 		$this->assertSame( $term_id, $found->term_id );
-		$this->assertContains( 'LIMIT 1', $wpdb->last_query );
+		$this->assertStringContainsString( 'LIMIT 1', $wpdb->last_query );
 	}
 
 	/**
diff --git a/tests/phpunit/tests/term/getTermLink.php b/tests/phpunit/tests/term/getTermLink.php
index b9a832e57a..74c6d19dc3 100644
--- a/tests/phpunit/tests/term/getTermLink.php
+++ b/tests/phpunit/tests/term/getTermLink.php
@@ -28,7 +28,7 @@ class Tests_Term_GetTermLink extends WP_UnitTestCase {
 		$term = (int) $t1;
 
 		$actual = get_term_link( $term, 'wptests_tax' );
-		$this->assertContains( 'wptests_tax=foo', $actual );
+		$this->assertStringContainsString( 'wptests_tax=foo', $actual );
 	}
 
 	public function test_numeric_string_should_be_interpreted_as_term_slug() {
@@ -48,7 +48,7 @@ class Tests_Term_GetTermLink extends WP_UnitTestCase {
 		$term = (string) $t1;
 
 		$actual = get_term_link( $term, 'wptests_tax' );
-		$this->assertContains( 'wptests_tax=' . $term, $actual );
+		$this->assertStringContainsString( 'wptests_tax=' . $term, $actual );
 	}
 
 	public function test_invalid_term_should_return_wp_error() {
@@ -60,7 +60,7 @@ class Tests_Term_GetTermLink extends WP_UnitTestCase {
 		$c = self::factory()->category->create();
 
 		$actual = get_term_link( $c, 'category' );
-		$this->assertContains( 'cat=' . $c, $actual );
+		$this->assertStringContainsString( 'cat=' . $c, $actual );
 	}
 
 	public function test_taxonomy_with_query_var_should_use_that_query_var_with_term_slug() {
@@ -80,7 +80,7 @@ class Tests_Term_GetTermLink extends WP_UnitTestCase {
 		);
 
 		$actual = get_term_link( $t, 'wptests_tax2' );
-		$this->assertContains( 'foo=bar', $actual );
+		$this->assertStringContainsString( 'foo=bar', $actual );
 	}
 
 	public function test_taxonomy_without_query_var_should_use_taxonomy_query_var_and_term_query_var_with_term_slug() {
@@ -100,8 +100,8 @@ class Tests_Term_GetTermLink extends WP_UnitTestCase {
 		);
 
 		$actual = get_term_link( $t, 'wptests_tax2' );
-		$this->assertContains( 'taxonomy=wptests_tax2', $actual );
-		$this->assertContains( 'term=bar', $actual );
+		$this->assertStringContainsString( 'taxonomy=wptests_tax2', $actual );
+		$this->assertStringContainsString( 'term=bar', $actual );
 	}
 
 	/**
@@ -131,7 +131,7 @@ class Tests_Term_GetTermLink extends WP_UnitTestCase {
 
 		remove_permastruct( 'wptests_tax2' );
 
-		$this->assertContains( '/foo/bar/', $actual );
+		$this->assertStringContainsString( '/foo/bar/', $actual );
 	}
 
 	public function test_taxonomy_permastruct_with_hierarchical_rewrite_should_put_term_ancestors_in_link() {
@@ -168,7 +168,7 @@ class Tests_Term_GetTermLink extends WP_UnitTestCase {
 
 		$actual = get_term_link( $t2, 'wptests_tax2' );
 
-		$this->assertContains( '/foo/term1/term2/', $actual );
+		$this->assertStringContainsString( '/foo/term1/term2/', $actual );
 	}
 
 	public function test_taxonomy_permastruct_with_nonhierarchical_rewrite_should_not_put_term_ancestors_in_link() {
@@ -205,6 +205,6 @@ class Tests_Term_GetTermLink extends WP_UnitTestCase {
 
 		$actual = get_term_link( $t2, 'wptests_tax2' );
 
-		$this->assertContains( '/foo/term2/', $actual );
+		$this->assertStringContainsString( '/foo/term2/', $actual );
 	}
 }
diff --git a/tests/phpunit/tests/term/query.php b/tests/phpunit/tests/term/query.php
index 6dbd2cb2f0..a34a3027a9 100644
--- a/tests/phpunit/tests/term/query.php
+++ b/tests/phpunit/tests/term/query.php
@@ -146,8 +146,8 @@ class Tests_Term_Query extends WP_UnitTestCase {
 		);
 		remove_filter( 'terms_clauses', array( $this, 'filter_terms_clauses' ) );
 
-		$this->assertContains( 'ORDER BY tt.term_id', $q->request );
-		$this->assertNotContains( 'ORDER BY ORDER BY', $q->request );
+		$this->assertStringContainsString( 'ORDER BY tt.term_id', $q->request );
+		$this->assertStringNotContainsString( 'ORDER BY ORDER BY', $q->request );
 	}
 
 	public function filter_terms_clauses( $clauses ) {
diff --git a/tests/phpunit/tests/term/wpGenerateTagCloud.php b/tests/phpunit/tests/term/wpGenerateTagCloud.php
index eecce41fe0..50597f67d9 100644
--- a/tests/phpunit/tests/term/wpGenerateTagCloud.php
+++ b/tests/phpunit/tests/term/wpGenerateTagCloud.php
@@ -83,7 +83,7 @@ class Tests_WP_Generate_Tag_Cloud extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( '>' . $tags[0]->name . '<', $found );
+		$this->assertStringContainsString( '>' . $tags[0]->name . '<', $found );
 	}
 
 	function test_hide_empty_false_format_array() {
@@ -107,7 +107,7 @@ class Tests_WP_Generate_Tag_Cloud extends WP_UnitTestCase {
 		);
 
 		$this->assertIsArray( $found );
-		$this->assertContains( '>' . $tags[0]->name . '<', $found[0] );
+		$this->assertStringContainsString( '>' . $tags[0]->name . '<', $found[0] );
 	}
 
 	function test_hide_empty_false_format_list() {
@@ -131,7 +131,7 @@ class Tests_WP_Generate_Tag_Cloud extends WP_UnitTestCase {
 
 		$this->assertRegExp( "|^<ul class='wp-tag-cloud' role='list'>|", $found );
 		$this->assertRegExp( "|</ul>\n|", $found );
-		$this->assertContains( '>' . $tags[0]->name . '<', $found );
+		$this->assertStringContainsString( '>' . $tags[0]->name . '<', $found );
 	}
 
 	function test_hide_empty_false_multi() {
@@ -157,7 +157,7 @@ class Tests_WP_Generate_Tag_Cloud extends WP_UnitTestCase {
 		);
 
 		foreach ( $tags as $tag ) {
-			$this->assertContains( '>' . $tag->name . '<', $found );
+			$this->assertStringContainsString( '>' . $tag->name . '<', $found );
 		}
 	}
 
@@ -188,7 +188,7 @@ class Tests_WP_Generate_Tag_Cloud extends WP_UnitTestCase {
 		$this->assertRegExp( "|</ul>\n|", $found );
 
 		foreach ( $tags as $tag ) {
-			$this->assertContains( '>' . $tag->name . '<', $found );
+			$this->assertStringContainsString( '>' . $tag->name . '<', $found );
 		}
 	}
 
@@ -224,8 +224,8 @@ class Tests_WP_Generate_Tag_Cloud extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( 'aria-label="' . $term_objects[0]->name . ' (Term has 1 post)"', $actual[0] );
-		$this->assertContains( 'aria-label="' . $term_objects[1]->name . ' (Term has 2 posts)"', $actual[1] );
+		$this->assertStringContainsString( 'aria-label="' . $term_objects[0]->name . ' (Term has 1 post)"', $actual[0] );
+		$this->assertStringContainsString( 'aria-label="' . $term_objects[1]->name . ' (Term has 2 posts)"', $actual[1] );
 	}
 
 	public function test_topic_count_text_callback() {
@@ -255,8 +255,8 @@ class Tests_WP_Generate_Tag_Cloud extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( 'aria-label="' . $term_objects[0]->name . ' (1 foo)"', $actual[0] );
-		$this->assertContains( 'aria-label="' . $term_objects[1]->name . ' (2 foo)"', $actual[1] );
+		$this->assertStringContainsString( 'aria-label="' . $term_objects[0]->name . ' (1 foo)"', $actual[0] );
+		$this->assertStringContainsString( 'aria-label="' . $term_objects[1]->name . ' (2 foo)"', $actual[1] );
 	}
 
 	/**
diff --git a/tests/phpunit/tests/theme/customHeader.php b/tests/phpunit/tests/theme/customHeader.php
index d59cab0eea..07496b9d0d 100644
--- a/tests/phpunit/tests/theme/customHeader.php
+++ b/tests/phpunit/tests/theme/customHeader.php
@@ -93,7 +93,7 @@ class Tests_Theme_CustomHeader extends WP_UnitTestCase {
 
 		$html = get_header_image_tag();
 		$this->assertStringStartsWith( '<img ', $html );
-		$this->assertContains( sprintf( 'src="%s"', $default ), $html );
+		$this->assertStringContainsString( sprintf( 'src="%s"', $default ), $html );
 	}
 
 	/**
@@ -116,7 +116,7 @@ class Tests_Theme_CustomHeader extends WP_UnitTestCase {
 		set_theme_mod( 'header_image', $custom );
 		$html = get_header_image_tag();
 		$this->assertStringStartsWith( '<img ', $html );
-		$this->assertContains( sprintf( 'src="%s"', $custom ), $html );
+		$this->assertStringContainsString( sprintf( 'src="%s"', $custom ), $html );
 	}
 
 	function test_get_custom_header_markup_without_registered_default_image() {
@@ -138,7 +138,7 @@ class Tests_Theme_CustomHeader extends WP_UnitTestCase {
 		$html = get_custom_header_markup();
 		$this->assertTrue( has_custom_header() );
 		$this->assertStringStartsWith( '<div id="wp-custom-header" class="wp-custom-header">', $html );
-		$this->assertContains( sprintf( 'src="%s"', $default ), $html );
+		$this->assertStringContainsString( sprintf( 'src="%s"', $default ), $html );
 	}
 
 	function test_get_header_video_url() {
diff --git a/tests/phpunit/tests/user.php b/tests/phpunit/tests/user.php
index 2e599e7ef4..8deccda474 100644
--- a/tests/phpunit/tests/user.php
+++ b/tests/phpunit/tests/user.php
@@ -1352,8 +1352,8 @@ class Tests_User extends WP_UnitTestCase {
 		$this->assertSame( $new_email, $recipient->address, 'Admin email change notification recipient not as expected' );
 
 		// Assert that HTML entites have been decode in body and subject.
-		$this->assertContains( '\'Test\' blog\'s "name" has <html entities> &', $email->subject, 'Email subject does not contain the decoded HTML entities' );
-		$this->assertNotContains( '&#039;Test&#039; blog&#039;s &quot;name&quot; has &lt;html entities&gt; &amp;', $email->subject, $email->subject, 'Email subject does contains HTML entities' );
+		$this->assertStringContainsString( '\'Test\' blog\'s "name" has <html entities> &', $email->subject, 'Email subject does not contain the decoded HTML entities' );
+		$this->assertStringNotContainsString( '&#039;Test&#039; blog&#039;s &quot;name&quot; has &lt;html entities&gt; &amp;', $email->subject, $email->subject, 'Email subject does contains HTML entities' );
 	}
 
 	/**
@@ -1655,8 +1655,8 @@ class Tests_User extends WP_UnitTestCase {
 		$this->assertSame( 'new-email@test.dev', $recipient->address, 'User email change confirmation recipient not as expected' );
 
 		// Assert that HTML entites have been decoded in body and subject.
-		$this->assertContains( '\'Test\' blog\'s "name" has <html entities> &', $email->subject, 'Email subject does not contain the decoded HTML entities' );
-		$this->assertNotContains( '&#039;Test&#039; blog&#039;s &quot;name&quot; has &lt;html entities&gt; &amp;', $email->subject, 'Email subject does contains HTML entities' );
+		$this->assertStringContainsString( '\'Test\' blog\'s "name" has <html entities> &', $email->subject, 'Email subject does not contain the decoded HTML entities' );
+		$this->assertStringNotContainsString( '&#039;Test&#039; blog&#039;s &quot;name&quot; has &lt;html entities&gt; &amp;', $email->subject, 'Email subject does contains HTML entities' );
 	}
 
 	/**
diff --git a/tests/phpunit/tests/user/author.php b/tests/phpunit/tests/user/author.php
index 21aa9f6b52..fc562be93e 100644
--- a/tests/phpunit/tests/user/author.php
+++ b/tests/phpunit/tests/user/author.php
@@ -114,9 +114,9 @@ class Tests_User_Author_Template extends WP_UnitTestCase {
 
 		$url = sprintf( 'http://%1$s/?author=%2$s', WP_TESTS_DOMAIN, $author->ID );
 
-		$this->assertContains( $url, $link );
-		$this->assertContains( 'Posts by Test Author', $link );
-		$this->assertContains( '>Test Author</a>', $link );
+		$this->assertStringContainsString( $url, $link );
+		$this->assertStringContainsString( 'Posts by Test Author', $link );
+		$this->assertStringContainsString( '>Test Author</a>', $link );
 
 		unset( $GLOBALS['authordata'] );
 	}
@@ -137,9 +137,9 @@ class Tests_User_Author_Template extends WP_UnitTestCase {
 
 		$this->set_permalink_structure( '' );
 
-		$this->assertContains( $url, $link );
-		$this->assertContains( 'Posts by Test Author', $link );
-		$this->assertContains( '>Test Author</a>', $link );
+		$this->assertStringContainsString( $url, $link );
+		$this->assertStringContainsString( 'Posts by Test Author', $link );
+		$this->assertStringContainsString( '>Test Author</a>', $link );
 
 		unset( $GLOBALS['authordata'] );
 	}
diff --git a/tests/phpunit/tests/user/query.php b/tests/phpunit/tests/user/query.php
index 41401d74ca..f0a0827038 100644
--- a/tests/phpunit/tests/user/query.php
+++ b/tests/phpunit/tests/user/query.php
@@ -175,7 +175,7 @@ class Tests_User_Query extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( "ORDER BY $full_key", $q->query_orderby );
+		$this->assertStringContainsString( "ORDER BY $full_key", $q->query_orderby );
 	}
 
 	public function orderby_should_convert_non_prefixed_keys_data() {
@@ -363,7 +363,7 @@ class Tests_User_Query extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( 'ORDER BY user_login', $q->query_orderby );
+		$this->assertStringContainsString( 'ORDER BY user_login', $q->query_orderby );
 	}
 
 	/**
@@ -381,7 +381,7 @@ class Tests_User_Query extends WP_UnitTestCase {
 		);
 
 		$expected_orderby = 'ORDER BY FIELD( ' . $wpdb->users . '.ID, ' . self::$author_ids[1] . ',' . self::$author_ids[0] . ',' . self::$author_ids[3] . ' )';
-		$this->assertContains( $expected_orderby, $q->query_orderby );
+		$this->assertStringContainsString( $expected_orderby, $q->query_orderby );
 
 		// assertEquals() respects order but ignores type (get_results() returns numeric strings).
 		$this->assertEquals( array( self::$author_ids[1], self::$author_ids[0], self::$author_ids[3] ), $q->get_results() );
@@ -402,7 +402,7 @@ class Tests_User_Query extends WP_UnitTestCase {
 		);
 
 		$expected_orderby = 'ORDER BY FIELD( ' . $wpdb->users . '.ID, ' . self::$author_ids[1] . ',' . self::$author_ids[0] . ',' . self::$author_ids[3] . ' )';
-		$this->assertContains( $expected_orderby, $q->query_orderby );
+		$this->assertStringContainsString( $expected_orderby, $q->query_orderby );
 
 		// assertEquals() respects order but ignores type (get_results() returns numeric strings).
 		$this->assertEquals( array( self::$author_ids[1], self::$author_ids[0], self::$author_ids[3] ), $q->get_results() );
@@ -419,7 +419,7 @@ class Tests_User_Query extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( 'ORDER BY user_login ASC, user_nicename ASC', $q->query_orderby );
+		$this->assertStringContainsString( 'ORDER BY user_login ASC, user_nicename ASC', $q->query_orderby );
 	}
 
 	/**
@@ -432,7 +432,7 @@ class Tests_User_Query extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( 'ORDER BY user_login ASC, user_nicename ASC', $q->query_orderby );
+		$this->assertStringContainsString( 'ORDER BY user_login ASC, user_nicename ASC', $q->query_orderby );
 	}
 
 	/**
@@ -445,7 +445,7 @@ class Tests_User_Query extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( 'ORDER BY user_login ASC, user_nicename ASC', $q->query_orderby );
+		$this->assertStringContainsString( 'ORDER BY user_login ASC, user_nicename ASC', $q->query_orderby );
 	}
 
 	/**
@@ -458,7 +458,7 @@ class Tests_User_Query extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( 'ORDER BY user_login', $q->query_orderby );
+		$this->assertStringContainsString( 'ORDER BY user_login', $q->query_orderby );
 	}
 
 	/**
@@ -475,7 +475,7 @@ class Tests_User_Query extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( 'ORDER BY user_login DESC, user_nicename ASC, user_email DESC', $q->query_orderby );
+		$this->assertStringContainsString( 'ORDER BY user_login DESC, user_nicename ASC, user_email DESC', $q->query_orderby );
 	}
 
 	/**
@@ -492,7 +492,7 @@ class Tests_User_Query extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertContains( 'ORDER BY user_login DESC, user_email ASC', $q->query_orderby );
+		$this->assertStringContainsString( 'ORDER BY user_login DESC, user_email ASC', $q->query_orderby );
 	}
 
 	/**
@@ -1065,7 +1065,7 @@ class Tests_User_Query extends WP_UnitTestCase {
 		$found    = wp_list_pluck( $q->get_results(), 'ID' );
 		$expected = array( self::$author_ids[0] );
 
-		$this->assertContains( "AND user_nicename = 'peter'", $q->query_where );
+		$this->assertStringContainsString( "AND user_nicename = 'peter'", $q->query_where );
 		$this->assertSameSets( $expected, $found );
 	}
 
@@ -1103,7 +1103,7 @@ class Tests_User_Query extends WP_UnitTestCase {
 		$found    = wp_list_pluck( $q->get_results(), 'ID' );
 		$expected = array( self::$author_ids[0], self::$author_ids[1], self::$author_ids[2] );
 
-		$this->assertContains( "AND user_nicename IN ( 'peter','paul','mary' )", $q->query_where );
+		$this->assertStringContainsString( "AND user_nicename IN ( 'peter','paul','mary' )", $q->query_where );
 		$this->assertSameSets( $expected, $found );
 	}
 
@@ -1141,7 +1141,7 @@ class Tests_User_Query extends WP_UnitTestCase {
 		$found_count    = count( $q->get_results() );
 		$expected_count = 10; // 13 total users minus 3 from query.
 
-		$this->assertContains( "AND user_nicename NOT IN ( 'peter','paul','mary' )", $q->query_where );
+		$this->assertStringContainsString( "AND user_nicename NOT IN ( 'peter','paul','mary' )", $q->query_where );
 		$this->assertSame( $expected_count, $found_count );
 	}
 
@@ -1180,7 +1180,7 @@ class Tests_User_Query extends WP_UnitTestCase {
 		$found    = wp_list_pluck( $q->get_results(), 'ID' );
 		$expected = array( self::$author_ids[2], self::$author_ids[0], self::$author_ids[1] );
 
-		$this->assertContains( "FIELD( user_nicename, 'mary','peter','paul' )", $q->query_orderby );
+		$this->assertStringContainsString( "FIELD( user_nicename, 'mary','peter','paul' )", $q->query_orderby );
 		$this->assertSame( $expected, $found );
 	}
 
@@ -1200,7 +1200,7 @@ class Tests_User_Query extends WP_UnitTestCase {
 		$found    = wp_list_pluck( $q->get_results(), 'ID' );
 		$expected = array( self::$author_ids[0] );
 
-		$this->assertContains( "AND user_login = '$user_login'", $q->query_where );
+		$this->assertStringContainsString( "AND user_login = '$user_login'", $q->query_where );
 		$this->assertSameSets( $expected, $found );
 	}
 
@@ -1221,7 +1221,7 @@ class Tests_User_Query extends WP_UnitTestCase {
 		$found    = wp_list_pluck( $q->get_results(), 'ID' );
 		$expected = array( self::$author_ids[0], self::$author_ids[1], self::$author_ids[2] );
 
-		$this->assertContains( "AND user_login IN ( '$user_login1','$user_login2','$user_login3' )", $q->query_where );
+		$this->assertStringContainsString( "AND user_login IN ( '$user_login1','$user_login2','$user_login3' )", $q->query_where );
 		$this->assertSameSets( $expected, $found );
 	}
 
@@ -1242,7 +1242,7 @@ class Tests_User_Query extends WP_UnitTestCase {
 		$found_count    = count( $q->get_results() );
 		$expected_count = 10; // 13 total users minus 3 from query.
 
-		$this->assertContains( "AND user_login NOT IN ( '$user_login1','$user_login2','$user_login3' )", $q->query_where );
+		$this->assertStringContainsString( "AND user_login NOT IN ( '$user_login1','$user_login2','$user_login3' )", $q->query_where );
 		$this->assertSame( $expected_count, $found_count );
 	}
 
@@ -1264,7 +1264,7 @@ class Tests_User_Query extends WP_UnitTestCase {
 		$found    = wp_list_pluck( $q->get_results(), 'ID' );
 		$expected = array( self::$author_ids[1], self::$author_ids[2], self::$author_ids[0] );
 
-		$this->assertContains( "FIELD( user_login, '$user_login2','$user_login3','$user_login1' )", $q->query_orderby );
+		$this->assertStringContainsString( "FIELD( user_login, '$user_login2','$user_login3','$user_login1' )", $q->query_orderby );
 		$this->assertSame( $expected, $found );
 	}
 
diff --git a/tests/phpunit/tests/user/wpDropdownUsers.php b/tests/phpunit/tests/user/wpDropdownUsers.php
index 91c35cf63a..98e9b76df6 100644
--- a/tests/phpunit/tests/user/wpDropdownUsers.php
+++ b/tests/phpunit/tests/user/wpDropdownUsers.php
@@ -28,7 +28,7 @@ class Tests_User_WpDropdownUsers extends WP_UnitTestCase {
 
 		$expected = "<option value='$u'>Foo Person</option>";
 
-		$this->assertContains( $expected, $found );
+		$this->assertStringContainsString( $expected, $found );
 	}
 
 	/**
@@ -54,7 +54,7 @@ class Tests_User_WpDropdownUsers extends WP_UnitTestCase {
 
 		$expected = "<option value='$u'>Foo Person</option>";
 
-		$this->assertContains( $expected, $found );
+		$this->assertStringContainsString( $expected, $found );
 	}
 
 	/**
@@ -80,7 +80,7 @@ class Tests_User_WpDropdownUsers extends WP_UnitTestCase {
 
 		$expected = "<option value='$u'>foo</option>";
 
-		$this->assertContains( $expected, $found );
+		$this->assertStringContainsString( $expected, $found );
 	}
 
 	/**
@@ -106,7 +106,7 @@ class Tests_User_WpDropdownUsers extends WP_UnitTestCase {
 
 		$expected = "<option value='$u'>Foo Person (foo)</option>";
 
-		$this->assertContains( $expected, $found );
+		$this->assertStringContainsString( $expected, $found );
 	}
 
 	/**
@@ -126,7 +126,7 @@ class Tests_User_WpDropdownUsers extends WP_UnitTestCase {
 		);
 
 		$user1 = get_userdata( $users[1] );
-		$this->assertContains( $user1->user_login, $found );
+		$this->assertStringContainsString( $user1->user_login, $found );
 	}
 
 	/**
@@ -142,7 +142,7 @@ class Tests_User_WpDropdownUsers extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertNotContains( (string) PHP_INT_MAX, $found );
+		$this->assertStringNotContainsString( (string) PHP_INT_MAX, $found );
 	}
 
 	/**
@@ -160,8 +160,8 @@ class Tests_User_WpDropdownUsers extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertNotContains( $u1->user_login, $found );
-		$this->assertContains( $u2->user_login, $found );
+		$this->assertStringNotContainsString( $u1->user_login, $found );
+		$this->assertStringContainsString( $u2->user_login, $found );
 	}
 
 	/**
@@ -179,8 +179,8 @@ class Tests_User_WpDropdownUsers extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertNotContains( $u1->user_login, $found );
-		$this->assertContains( $u2->user_login, $found );
+		$this->assertStringNotContainsString( $u1->user_login, $found );
+		$this->assertStringContainsString( $u2->user_login, $found );
 	}
 
 	/**
@@ -198,7 +198,7 @@ class Tests_User_WpDropdownUsers extends WP_UnitTestCase {
 			)
 		);
 
-		$this->assertNotContains( $u1->user_login, $found );
-		$this->assertContains( $u2->user_login, $found );
+		$this->assertStringNotContainsString( $u1->user_login, $found );
+		$this->assertStringContainsString( $u2->user_login, $found );
 	}
 }
diff --git a/tests/phpunit/tests/user/wpSendUserRequest.php b/tests/phpunit/tests/user/wpSendUserRequest.php
index d3ab887939..a6b86af18d 100644
--- a/tests/phpunit/tests/user/wpSendUserRequest.php
+++ b/tests/phpunit/tests/user/wpSendUserRequest.php
@@ -109,9 +109,9 @@ class Tests_User_WpSendUserRequest extends WP_UnitTestCase {
 
 		$this->assertTrue( $result );
 		$this->assertSame( self::$test_user->user_email, $mailer->get_recipient( 'to' )->address );
-		$this->assertContains( 'Confirm Action: Export Personal Data', $mailer->get_sent()->subject );
-		$this->assertContains( 'action=confirmaction&request_id=', $mailer->get_sent()->body );
-		$this->assertContains( 'Export Personal Data', $mailer->get_sent()->body );
+		$this->assertStringContainsString( 'Confirm Action: Export Personal Data', $mailer->get_sent()->subject );
+		$this->assertStringContainsString( 'action=confirmaction&request_id=', $mailer->get_sent()->body );
+		$this->assertStringContainsString( 'Export Personal Data', $mailer->get_sent()->body );
 	}
 
 	/**
@@ -127,9 +127,9 @@ class Tests_User_WpSendUserRequest extends WP_UnitTestCase {
 
 		$this->assertTrue( $result );
 		$this->assertSame( self::$test_user->user_email, $mailer->get_recipient( 'to' )->address );
-		$this->assertContains( 'Confirm Action: Erase Personal Data', $mailer->get_sent()->subject );
-		$this->assertContains( 'action=confirmaction&request_id=', $mailer->get_sent()->body );
-		$this->assertContains( 'Erase Personal Data', $mailer->get_sent()->body );
+		$this->assertStringContainsString( 'Confirm Action: Erase Personal Data', $mailer->get_sent()->subject );
+		$this->assertStringContainsString( 'action=confirmaction&request_id=', $mailer->get_sent()->body );
+		$this->assertStringContainsString( 'Erase Personal Data', $mailer->get_sent()->body );
 	}
 
 	/**
@@ -145,9 +145,9 @@ class Tests_User_WpSendUserRequest extends WP_UnitTestCase {
 
 		$this->assertTrue( $result );
 		$this->assertSame( self::$test_user->user_email, $mailer->get_recipient( 'to' )->address );
-		$this->assertContains( 'Confirm Action: Export Personal Data', $mailer->get_sent()->subject );
-		$this->assertContains( 'action=confirmaction&request_id=', $mailer->get_sent()->body );
-		$this->assertContains( 'Export Personal Data', $mailer->get_sent()->body );
+		$this->assertStringContainsString( 'Confirm Action: Export Personal Data', $mailer->get_sent()->subject );
+		$this->assertStringContainsString( 'action=confirmaction&request_id=', $mailer->get_sent()->body );
+		$this->assertStringContainsString( 'Export Personal Data', $mailer->get_sent()->body );
 	}
 
 	/**
@@ -163,9 +163,9 @@ class Tests_User_WpSendUserRequest extends WP_UnitTestCase {
 
 		$this->assertTrue( $result );
 		$this->assertSame( self::$test_user->user_email, $mailer->get_recipient( 'to' )->address );
-		$this->assertContains( 'Confirm Action: Erase Personal Data', $mailer->get_sent()->subject );
-		$this->assertContains( 'action=confirmaction&request_id=', $mailer->get_sent()->body );
-		$this->assertContains( 'Erase Personal Data', $mailer->get_sent()->body );
+		$this->assertStringContainsString( 'Confirm Action: Erase Personal Data', $mailer->get_sent()->subject );
+		$this->assertStringContainsString( 'action=confirmaction&request_id=', $mailer->get_sent()->body );
+		$this->assertStringContainsString( 'Erase Personal Data', $mailer->get_sent()->body );
 	}
 
 	/**
@@ -209,7 +209,7 @@ class Tests_User_WpSendUserRequest extends WP_UnitTestCase {
 		$mailer = tests_retrieve_phpmailer_instance();
 
 		$this->assertTrue( $result );
-		$this->assertContains( 'Custom Email Content.', $mailer->get_sent()->body );
+		$this->assertStringContainsString( 'Custom Email Content.', $mailer->get_sent()->body );
 	}
 
 	/**
@@ -239,7 +239,7 @@ class Tests_User_WpSendUserRequest extends WP_UnitTestCase {
 
 		$mailer = tests_retrieve_phpmailer_instance();
 
-		$this->assertContains( 'From: Tester <tester@example.com>', $mailer->get_sent()->header );
+		$this->assertStringContainsString( 'From: Tester <tester@example.com>', $mailer->get_sent()->header );
 	}
 
 	/**
@@ -288,7 +288,7 @@ class Tests_User_WpSendUserRequest extends WP_UnitTestCase {
 		wp_send_user_request( $request_id );
 		$mailer = tests_retrieve_phpmailer_instance();
 
-		$this->assertContains( 'Confirmar la', $mailer->get_sent()->subject );
+		$this->assertStringContainsString( 'Confirmar la', $mailer->get_sent()->subject );
 	}
 
 	/**
@@ -310,7 +310,7 @@ class Tests_User_WpSendUserRequest extends WP_UnitTestCase {
 		wp_send_user_request( $request_id );
 		$mailer = tests_retrieve_phpmailer_instance();
 
-		$this->assertContains( 'Aktion bestätigen', $mailer->get_sent()->subject );
+		$this->assertStringContainsString( 'Aktion bestätigen', $mailer->get_sent()->subject );
 	}
 
 	/**
@@ -332,7 +332,7 @@ class Tests_User_WpSendUserRequest extends WP_UnitTestCase {
 		wp_send_user_request( $request_id );
 		$mailer = tests_retrieve_phpmailer_instance();
 
-		$this->assertContains( 'Confirmar la', $mailer->get_sent()->subject );
+		$this->assertStringContainsString( 'Confirmar la', $mailer->get_sent()->subject );
 	}
 
 	/**
@@ -356,7 +356,7 @@ class Tests_User_WpSendUserRequest extends WP_UnitTestCase {
 		wp_send_user_request( $request_id );
 		$mailer = tests_retrieve_phpmailer_instance();
 
-		$this->assertContains( 'Confirm Action', $mailer->get_sent()->subject );
+		$this->assertStringContainsString( 'Confirm Action', $mailer->get_sent()->subject );
 	}
 
 	/**
@@ -375,7 +375,7 @@ class Tests_User_WpSendUserRequest extends WP_UnitTestCase {
 		wp_send_user_request( $request_id );
 		$mailer = tests_retrieve_phpmailer_instance();
 
-		$this->assertContains( 'Confirm Action', $mailer->get_sent()->subject );
+		$this->assertStringContainsString( 'Confirm Action', $mailer->get_sent()->subject );
 	}
 
 	/**
@@ -397,6 +397,6 @@ class Tests_User_WpSendUserRequest extends WP_UnitTestCase {
 		wp_send_user_request( $request_id );
 		$mailer = tests_retrieve_phpmailer_instance();
 
-		$this->assertContains( 'Confirmar la', $mailer->get_sent()->subject );
+		$this->assertStringContainsString( 'Confirmar la', $mailer->get_sent()->subject );
 	}
 }
diff --git a/tests/phpunit/tests/widgets.php b/tests/phpunit/tests/widgets.php
index 327f43b87c..f8ab1a26e8 100644
--- a/tests/phpunit/tests/widgets.php
+++ b/tests/phpunit/tests/widgets.php
@@ -264,8 +264,8 @@ class Tests_Widgets extends WP_UnitTestCase {
 		);
 
 		$this->assertArrayHasKey( $sidebar_id, $wp_registered_sidebars );
-		$this->assertContains( '<div id="%1$s" class="before-sidebar %2$s">', $wp_registered_sidebars[ $sidebar_id ]['before_sidebar'] );
-		$this->assertContains( '</div> <!-- .before-sidebar -->', $wp_registered_sidebars[ $sidebar_id ]['after_sidebar'] );
+		$this->assertStringContainsString( '<div id="%1$s" class="before-sidebar %2$s">', $wp_registered_sidebars[ $sidebar_id ]['before_sidebar'] );
+		$this->assertStringContainsString( '</div> <!-- .before-sidebar -->', $wp_registered_sidebars[ $sidebar_id ]['after_sidebar'] );
 
 	}
 
@@ -378,10 +378,10 @@ class Tests_Widgets extends WP_UnitTestCase {
 		$widget->_set( 2 );
 		$widget->widget( $args, $instance );
 		$output = ob_get_clean();
-		$this->assertNotContains( 'no-options-widget', $output );
-		$this->assertContains( '<h2>Buscar</h2>', $output );
-		$this->assertContains( '<section>', $output );
-		$this->assertContains( '</section>', $output );
+		$this->assertStringNotContainsString( 'no-options-widget', $output );
+		$this->assertStringContainsString( '<h2>Buscar</h2>', $output );
+		$this->assertStringContainsString( '<section>', $output );
+		$this->assertStringContainsString( '</section>', $output );
 	}
 
 	/**
@@ -393,7 +393,7 @@ class Tests_Widgets extends WP_UnitTestCase {
 		$retval = $widget->form( array() );
 		$output = ob_get_clean();
 		$this->assertSame( 'noform', $retval );
-		$this->assertContains( 'no-options-widget', $output );
+		$this->assertStringContainsString( 'no-options-widget', $output );
 	}
 
 	/**
@@ -740,19 +740,19 @@ class Tests_Widgets extends WP_UnitTestCase {
 		$control = ob_get_clean();
 		$this->assertNotEmpty( $control );
 
-		$this->assertContains( '<div class="widget-top">', $control );
-		$this->assertContains( '<div class="widget-title-action">', $control );
-		$this->assertContains( '<div class="widget-title">', $control );
-		$this->assertContains( '<form method="post">', $control );
-		$this->assertContains( '<div class="widget-content">', $control );
-		$this->assertContains( '<input class="widefat"', $control );
-		$this->assertContains( '<input type="hidden" name="id_base" class="id_base" value="search"', $control );
-		$this->assertContains( '<div class="widget-control-actions">', $control );
-		$this->assertContains( '<div class="alignleft">', $control );
-		$this->assertContains( 'widget-control-remove', $control );
-		$this->assertContains( 'widget-control-close', $control );
-		$this->assertContains( '<div class="alignright">', $control );
-		$this->assertContains( '<input type="submit" name="savewidget"', $control );
+		$this->assertStringContainsString( '<div class="widget-top">', $control );
+		$this->assertStringContainsString( '<div class="widget-title-action">', $control );
+		$this->assertStringContainsString( '<div class="widget-title">', $control );
+		$this->assertStringContainsString( '<form method="post">', $control );
+		$this->assertStringContainsString( '<div class="widget-content">', $control );
+		$this->assertStringContainsString( '<input class="widefat"', $control );
+		$this->assertStringContainsString( '<input type="hidden" name="id_base" class="id_base" value="search"', $control );
+		$this->assertStringContainsString( '<div class="widget-control-actions">', $control );
+		$this->assertStringContainsString( '<div class="alignleft">', $control );
+		$this->assertStringContainsString( 'widget-control-remove', $control );
+		$this->assertStringContainsString( 'widget-control-close', $control );
+		$this->assertStringContainsString( '<div class="alignright">', $control );
+		$this->assertStringContainsString( '<input type="submit" name="savewidget"', $control );
 
 		$param_overrides = array(
 			'before_form'           => '<!-- before_form -->',
@@ -771,11 +771,11 @@ class Tests_Widgets extends WP_UnitTestCase {
 		wp_widget_control( ...$sidebar_args );
 		$control = ob_get_clean();
 		$this->assertNotEmpty( $control );
-		$this->assertNotContains( '<form method="post">', $control );
-		$this->assertNotContains( '<div class="widget-content">', $control );
+		$this->assertStringNotContainsString( '<form method="post">', $control );
+		$this->assertStringNotContainsString( '<div class="widget-content">', $control );
 
 		foreach ( $param_overrides as $contained ) {
-			$this->assertContains( $contained, $control );
+			$this->assertStringContainsString( $contained, $control );
 		}
 	}
 
diff --git a/tests/phpunit/tests/widgets/custom-html-widget.php b/tests/phpunit/tests/widgets/custom-html-widget.php
index 6447f5ec2d..597a872e78 100644
--- a/tests/phpunit/tests/widgets/custom-html-widget.php
+++ b/tests/phpunit/tests/widgets/custom-html-widget.php
@@ -111,12 +111,12 @@ class Test_WP_Widget_Custom_HTML extends WP_UnitTestCase {
 		$output = ob_get_clean();
 		$this->assertNotEmpty( $this->widget_custom_html_content_args );
 		$this->assertNotEmpty( $this->widget_text_args );
-		$this->assertContains( '[filter:widget_text][filter:widget_custom_html_content]', $output );
-		$this->assertContains( '<section id="custom_html-5" class="widget_text widget widget_custom_html">', $output );
-		$this->assertContains( '<div class="textwidget custom-html-widget">', $output );
-		$this->assertNotContains( '<p>', $output );
-		$this->assertNotContains( '<br>', $output );
-		$this->assertNotContains( '</u>', $output );
+		$this->assertStringContainsString( '[filter:widget_text][filter:widget_custom_html_content]', $output );
+		$this->assertStringContainsString( '<section id="custom_html-5" class="widget_text widget widget_custom_html">', $output );
+		$this->assertStringContainsString( '<div class="textwidget custom-html-widget">', $output );
+		$this->assertStringNotContainsString( '<p>', $output );
+		$this->assertStringNotContainsString( '<br>', $output );
+		$this->assertStringNotContainsString( '</u>', $output );
 		$this->assertSame( $text_widget_instance, $this->widget_text_args[1] );
 		$this->assertSame( $instance, $this->widget_custom_html_content_args[1] );
 		$this->assertSame( $widget, $this->widget_text_args[2] );
@@ -128,7 +128,7 @@ class Test_WP_Widget_Custom_HTML extends WP_UnitTestCase {
 		ob_start();
 		$widget->widget( $args, $instance );
 		$output = ob_get_clean();
-		$this->assertContains( '</u>', $output );
+		$this->assertStringContainsString( '</u>', $output );
 	}
 
 	/**
@@ -287,7 +287,7 @@ class Test_WP_Widget_Custom_HTML extends WP_UnitTestCase {
 		WP_Widget_Custom_HTML::render_control_template_scripts();
 		$output = ob_get_clean();
 
-		$this->assertContains( '<script type="text/html" id="tmpl-widget-custom-html-control-fields">', $output );
+		$this->assertStringContainsString( '<script type="text/html" id="tmpl-widget-custom-html-control-fields">', $output );
 	}
 
 	/**
@@ -300,7 +300,7 @@ class Test_WP_Widget_Custom_HTML extends WP_UnitTestCase {
 		WP_Widget_Custom_HTML::add_help_text();
 		$help_tab = get_current_screen()->get_help_tab( 'custom_html_widget' );
 
-		$this->assertContains( 'Use the Custom HTML widget to add arbitrary HTML code to your widget areas.', $help_tab['content'] );
+		$this->assertStringContainsString( 'Use the Custom HTML widget to add arbitrary HTML code to your widget areas.', $help_tab['content'] );
 	}
 
 	/**
@@ -326,7 +326,7 @@ class Test_WP_Widget_Custom_HTML extends WP_UnitTestCase {
 		);
 
 		$output = get_echo( array( $widget, 'widget' ), array( $args, $instance ) );
-		$this->assertContains( 'rel="noopener"', $output );
+		$this->assertStringContainsString( 'rel="noopener"', $output );
 	}
 
 	/**
@@ -352,7 +352,7 @@ class Test_WP_Widget_Custom_HTML extends WP_UnitTestCase {
 		);
 
 		$output = get_echo( array( $widget, 'widget' ), array( $args, $instance ) );
-		$this->assertNotContains( 'rel="noopener"', $output );
+		$this->assertStringNotContainsString( 'rel="noopener"', $output );
 	}
 
 }
diff --git a/tests/phpunit/tests/widgets/media-audio-widget.php b/tests/phpunit/tests/widgets/media-audio-widget.php
index a4e3afd60f..7655b00d98 100644
--- a/tests/phpunit/tests/widgets/media-audio-widget.php
+++ b/tests/phpunit/tests/widgets/media-audio-widget.php
@@ -255,9 +255,9 @@ class Test_WP_Widget_Media_Audio extends WP_UnitTestCase {
 		$output = ob_get_clean();
 
 		// Check default outputs.
-		$this->assertContains( 'preload="none"', $output );
-		$this->assertContains( 'class="wp-audio-shortcode"', $output );
-		$this->assertContains( 'small-audio.mp3', $output );
+		$this->assertStringContainsString( 'preload="none"', $output );
+		$this->assertStringContainsString( 'class="wp-audio-shortcode"', $output );
+		$this->assertStringContainsString( 'small-audio.mp3', $output );
 
 		ob_start();
 		$widget->render_media(
@@ -271,8 +271,8 @@ class Test_WP_Widget_Media_Audio extends WP_UnitTestCase {
 		$output = ob_get_clean();
 
 		// Custom attributes.
-		$this->assertContains( 'preload="auto"', $output );
-		$this->assertContains( 'loop="1"', $output );
+		$this->assertStringContainsString( 'preload="auto"', $output );
+		$this->assertStringContainsString( 'loop="1"', $output );
 	}
 
 	/**
@@ -322,6 +322,6 @@ class Test_WP_Widget_Media_Audio extends WP_UnitTestCase {
 		$widget->render_control_template_scripts();
 		$output = ob_get_clean();
 
-		$this->assertContains( '<script type="text/html" id="tmpl-wp-media-widget-audio-preview">', $output );
+		$this->assertStringContainsString( '<script type="text/html" id="tmpl-wp-media-widget-audio-preview">', $output );
 	}
 }
diff --git a/tests/phpunit/tests/widgets/media-gallery-widget.php b/tests/phpunit/tests/widgets/media-gallery-widget.php
index 1e67497833..9ad9e2864f 100644
--- a/tests/phpunit/tests/widgets/media-gallery-widget.php
+++ b/tests/phpunit/tests/widgets/media-gallery-widget.php
@@ -81,10 +81,10 @@ class Test_WP_Widget_Media_Gallery extends WP_UnitTestCase {
 		$widget->render_media( $instance );
 		$output = ob_get_clean();
 
-		$this->assertContains( 'gallery-columns-3', $output );
-		$this->assertContains( 'gallery-size-thumbnail', $output );
-		$this->assertContains( 'canola', $output );
-		$this->assertContains( 'waffles', $output );
+		$this->assertStringContainsString( 'gallery-columns-3', $output );
+		$this->assertStringContainsString( 'gallery-size-thumbnail', $output );
+		$this->assertStringContainsString( 'canola', $output );
+		$this->assertStringContainsString( 'waffles', $output );
 	}
 
 	/**
@@ -103,7 +103,7 @@ class Test_WP_Widget_Media_Gallery extends WP_UnitTestCase {
 		$this->assertTrue( wp_script_is( 'media-gallery-widget' ) );
 
 		$after = implode( '', wp_scripts()->registered['media-gallery-widget']->extra['after'] );
-		$this->assertContains( 'wp.mediaWidgets.modelConstructors[ "media_gallery" ].prototype', $after );
+		$this->assertStringContainsString( 'wp.mediaWidgets.modelConstructors[ "media_gallery" ].prototype', $after );
 	}
 
 	/**
@@ -199,6 +199,6 @@ class Test_WP_Widget_Media_Gallery extends WP_UnitTestCase {
 		$widget->render_control_template_scripts();
 		$output = ob_get_clean();
 
-		$this->assertContains( '<script type="text/html" id="tmpl-wp-media-widget-gallery-preview">', $output );
+		$this->assertStringContainsString( '<script type="text/html" id="tmpl-wp-media-widget-gallery-preview">', $output );
 	}
 }
diff --git a/tests/phpunit/tests/widgets/media-image-widget.php b/tests/phpunit/tests/widgets/media-image-widget.php
index 64d02803c0..60f8bf184a 100644
--- a/tests/phpunit/tests/widgets/media-image-widget.php
+++ b/tests/phpunit/tests/widgets/media-image-widget.php
@@ -450,11 +450,11 @@ class Test_WP_Widget_Media_Image extends WP_UnitTestCase {
 		$output = ob_get_clean();
 
 		// No default title.
-		$this->assertNotContains( 'title="', $output );
+		$this->assertStringNotContainsString( 'title="', $output );
 		// Default image classes.
-		$this->assertContains( 'class="image wp-image-' . $attachment_id, $output );
-		$this->assertContains( 'style="max-width: 100%; height: auto;"', $output );
-		$this->assertContains( 'alt=""', $output );
+		$this->assertStringContainsString( 'class="image wp-image-' . $attachment_id, $output );
+		$this->assertStringContainsString( 'style="max-width: 100%; height: auto;"', $output );
+		$this->assertStringContainsString( 'alt=""', $output );
 
 		ob_start();
 		$widget->render_media(
@@ -471,12 +471,12 @@ class Test_WP_Widget_Media_Image extends WP_UnitTestCase {
 		$output = ob_get_clean();
 
 		// Custom image title.
-		$this->assertContains( 'title="Custom Title"', $output );
+		$this->assertStringContainsString( 'title="Custom Title"', $output );
 		// Custom image class.
-		$this->assertContains( 'class="image wp-image-' . $attachment_id . ' custom-class', $output );
-		$this->assertContains( 'alt="A flower"', $output );
-		$this->assertContains( 'width="100"', $output );
-		$this->assertContains( 'height="100"', $output );
+		$this->assertStringContainsString( 'class="image wp-image-' . $attachment_id . ' custom-class', $output );
+		$this->assertStringContainsString( 'alt="A flower"', $output );
+		$this->assertStringContainsString( 'width="100"', $output );
+		$this->assertStringContainsString( 'height="100"', $output );
 
 		// Embeded images.
 		ob_start();
@@ -493,7 +493,7 @@ class Test_WP_Widget_Media_Image extends WP_UnitTestCase {
 		$output = ob_get_clean();
 
 		// Custom image class.
-		$this->assertContains( 'src="http://example.org/url/to/image.jpg"', $output );
+		$this->assertStringContainsString( 'src="http://example.org/url/to/image.jpg"', $output );
 
 		// Link settings.
 		ob_start();
@@ -506,11 +506,11 @@ class Test_WP_Widget_Media_Image extends WP_UnitTestCase {
 		$output = ob_get_clean();
 
 		$link = '<a href="' . wp_get_attachment_url( $attachment_id ) . '"';
-		$this->assertContains( $link, $output );
+		$this->assertStringContainsString( $link, $output );
 		$this->assertTrue( (bool) preg_match( '#<a href.*?>#', $output, $matches ) );
-		$this->assertNotContains( ' class="', $matches[0] );
-		$this->assertNotContains( ' rel="', $matches[0] );
-		$this->assertNotContains( ' target="', $matches[0] );
+		$this->assertStringNotContainsString( ' class="', $matches[0] );
+		$this->assertStringNotContainsString( ' rel="', $matches[0] );
+		$this->assertStringNotContainsString( ' target="', $matches[0] );
 
 		ob_start();
 		$widget->render_media(
@@ -524,10 +524,10 @@ class Test_WP_Widget_Media_Image extends WP_UnitTestCase {
 		);
 		$output = ob_get_clean();
 
-		$this->assertContains( '<a href="' . get_attachment_link( $attachment_id ) . '"', $output );
-		$this->assertContains( 'class="custom-link-class"', $output );
-		$this->assertContains( 'rel="attachment"', $output );
-		$this->assertNotContains( 'target=""', $output );
+		$this->assertStringContainsString( '<a href="' . get_attachment_link( $attachment_id ) . '"', $output );
+		$this->assertStringContainsString( 'class="custom-link-class"', $output );
+		$this->assertStringContainsString( 'rel="attachment"', $output );
+		$this->assertStringNotContainsString( 'target=""', $output );
 
 		ob_start();
 		$widget->render_media(
@@ -540,9 +540,9 @@ class Test_WP_Widget_Media_Image extends WP_UnitTestCase {
 		);
 		$output = ob_get_clean();
 
-		$this->assertContains( '<a href="https://example.org"', $output );
-		$this->assertContains( 'target="_blank"', $output );
-		$this->assertContains( 'rel="noopener"', $output );
+		$this->assertStringContainsString( '<a href="https://example.org"', $output );
+		$this->assertStringContainsString( 'target="_blank"', $output );
+		$this->assertStringContainsString( 'rel="noopener"', $output );
 
 		// Populate caption in attachment.
 		wp_update_post(
@@ -560,8 +560,8 @@ class Test_WP_Widget_Media_Image extends WP_UnitTestCase {
 			)
 		);
 		$output = ob_get_clean();
-		$this->assertNotContains( 'wp-caption', $output );
-		$this->assertNotContains( '<p class="wp-caption-text">', $output );
+		$this->assertStringNotContainsString( 'wp-caption', $output );
+		$this->assertStringNotContainsString( '<p class="wp-caption-text">', $output );
 
 		// If the caption is explicitly null, then the caption of the underlying attachment will be displayed.
 		ob_start();
@@ -572,8 +572,8 @@ class Test_WP_Widget_Media_Image extends WP_UnitTestCase {
 			)
 		);
 		$output = ob_get_clean();
-		$this->assertContains( 'class="wp-caption alignnone"', $output );
-		$this->assertContains( '<p class="wp-caption-text">Default caption</p>', $output );
+		$this->assertStringContainsString( 'class="wp-caption alignnone"', $output );
+		$this->assertStringContainsString( '<p class="wp-caption-text">Default caption</p>', $output );
 
 		// If caption is provided, then it will be displayed.
 		ob_start();
@@ -584,8 +584,8 @@ class Test_WP_Widget_Media_Image extends WP_UnitTestCase {
 			)
 		);
 		$output = ob_get_clean();
-		$this->assertContains( 'class="wp-caption alignnone"', $output );
-		$this->assertContains( '<p class="wp-caption-text">Custom caption</p>', $output );
+		$this->assertStringContainsString( 'class="wp-caption alignnone"', $output );
+		$this->assertStringContainsString( '<p class="wp-caption-text">Custom caption</p>', $output );
 
 		// Attachments with custom sizes can render captions.
 		ob_start();
@@ -599,8 +599,8 @@ class Test_WP_Widget_Media_Image extends WP_UnitTestCase {
 			)
 		);
 		$output = ob_get_clean();
-		$this->assertContains( 'style="width: 310px"', $output );
-		$this->assertContains( '<p class="wp-caption-text">Caption for an image with custom size</p>', $output );
+		$this->assertStringContainsString( 'style="width: 310px"', $output );
+		$this->assertStringContainsString( '<p class="wp-caption-text">Caption for an image with custom size</p>', $output );
 	}
 
 	/**
@@ -628,6 +628,6 @@ class Test_WP_Widget_Media_Image extends WP_UnitTestCase {
 		$widget->render_control_template_scripts();
 		$output = ob_get_clean();
 
-		$this->assertContains( '<script type="text/html" id="tmpl-wp-media-widget-image-preview">', $output );
+		$this->assertStringContainsString( '<script type="text/html" id="tmpl-wp-media-widget-image-preview">', $output );
 	}
 }
diff --git a/tests/phpunit/tests/widgets/media-video-widget.php b/tests/phpunit/tests/widgets/media-video-widget.php
index b33bce8353..b1e665d061 100644
--- a/tests/phpunit/tests/widgets/media-video-widget.php
+++ b/tests/phpunit/tests/widgets/media-video-widget.php
@@ -257,12 +257,12 @@ class Test_WP_Widget_Media_Video extends WP_UnitTestCase {
 		$output = ob_get_clean();
 
 		// Check default outputs.
-		$this->assertContains( 'preload="metadata"', $output );
-		$this->assertContains( 'class="wp-video"', $output );
-		$this->assertContains( 'width:100%', $output );
-		$this->assertNotContains( 'height=', $output );
-		$this->assertNotContains( 'width="', $output );
-		$this->assertContains( 'small-video.m4v', $output );// Auto parses dimensions.
+		$this->assertStringContainsString( 'preload="metadata"', $output );
+		$this->assertStringContainsString( 'class="wp-video"', $output );
+		$this->assertStringContainsString( 'width:100%', $output );
+		$this->assertStringNotContainsString( 'height=', $output );
+		$this->assertStringNotContainsString( 'width="', $output );
+		$this->assertStringContainsString( 'small-video.m4v', $output );// Auto parses dimensions.
 
 		ob_start();
 		$widget->render_media(
@@ -276,8 +276,8 @@ class Test_WP_Widget_Media_Video extends WP_UnitTestCase {
 		$output = ob_get_clean();
 
 		// Custom attributes.
-		$this->assertContains( 'preload="metadata"', $output );
-		$this->assertContains( 'loop="1"', $output );
+		$this->assertStringContainsString( 'preload="metadata"', $output );
+		$this->assertStringContainsString( 'loop="1"', $output );
 
 		// Externally hosted video.
 		ob_start();
@@ -293,9 +293,9 @@ class Test_WP_Widget_Media_Video extends WP_UnitTestCase {
 		$output = ob_get_clean();
 
 		// Custom attributes.
-		$this->assertContains( 'preload="metadata"', $output );
-		$this->assertContains( 'src="https://www.youtube.com/watch?v=72xdCU__XCk', $output );
-		$this->assertContains( $content, $output );
+		$this->assertStringContainsString( 'preload="metadata"', $output );
+		$this->assertStringContainsString( 'src="https://www.youtube.com/watch?v=72xdCU__XCk', $output );
+		$this->assertStringContainsString( $content, $output );
 	}
 
 	/**
@@ -350,6 +350,6 @@ class Test_WP_Widget_Media_Video extends WP_UnitTestCase {
 		$widget->render_control_template_scripts();
 		$output = ob_get_clean();
 
-		$this->assertContains( '<script type="text/html" id="tmpl-wp-media-widget-video-preview">', $output );
+		$this->assertStringContainsString( '<script type="text/html" id="tmpl-wp-media-widget-video-preview">', $output );
 	}
 }
diff --git a/tests/phpunit/tests/widgets/media-widget.php b/tests/phpunit/tests/widgets/media-widget.php
index ebe150d4f9..ba9b305979 100644
--- a/tests/phpunit/tests/widgets/media-widget.php
+++ b/tests/phpunit/tests/widgets/media-widget.php
@@ -341,9 +341,9 @@ class Test_WP_Widget_Media extends WP_UnitTestCase {
 		$this->assertSame( $widget, $this->widget_instance_filter_args[2] );
 		$output = ob_get_clean();
 
-		$this->assertContains( '<h2>Foo</h2>', $output );
-		$this->assertContains( '<section>', $output );
-		$this->assertContains( '</section>', $output );
+		$this->assertStringContainsString( '<h2>Foo</h2>', $output );
+		$this->assertStringContainsString( '<section>', $output );
+		$this->assertStringContainsString( '</section>', $output );
 
 		// No title.
 		ob_start();
@@ -352,7 +352,7 @@ class Test_WP_Widget_Media extends WP_UnitTestCase {
 		$widget->expects( $this->atLeastOnce() )->method( 'render_media' )->with( $instance );
 		$widget->widget( $args, $instance );
 		$output = ob_get_clean();
-		$this->assertNotContains( '<h2>Foo</h2>', $output );
+		$this->assertStringNotContainsString( '<h2>Foo</h2>', $output );
 
 		// No attachment_id nor url.
 		$instance['url']           = '';
@@ -396,9 +396,9 @@ class Test_WP_Widget_Media extends WP_UnitTestCase {
 		$widget->form( array() );
 		$output = ob_get_clean();
 
-		$this->assertContains( 'name="widget-mocked[][attachment_id]"', $output );
-		$this->assertContains( 'name="widget-mocked[][title]"', $output );
-		$this->assertContains( 'name="widget-mocked[][url]"', $output );
+		$this->assertStringContainsString( 'name="widget-mocked[][attachment_id]"', $output );
+		$this->assertStringContainsString( 'name="widget-mocked[][title]"', $output );
+		$this->assertStringContainsString( 'name="widget-mocked[][url]"', $output );
 	}
 
 	/**
@@ -468,7 +468,7 @@ class Test_WP_Widget_Media extends WP_UnitTestCase {
 		$widget->render_control_template_scripts();
 		$output = ob_get_clean();
 
-		$this->assertContains( '<script type="text/html" id="tmpl-widget-media-mocked-control">', $output );
+		$this->assertStringContainsString( '<script type="text/html" id="tmpl-widget-media-mocked-control">', $output );
 	}
 
 	/**
diff --git a/tests/phpunit/tests/widgets/text-widget.php b/tests/phpunit/tests/widgets/text-widget.php
index 4885876c76..f216176463 100644
--- a/tests/phpunit/tests/widgets/text-widget.php
+++ b/tests/phpunit/tests/widgets/text-widget.php
@@ -153,12 +153,12 @@ class Test_WP_Widget_Text extends WP_UnitTestCase {
 		);
 		$widget->widget( $args, $instance );
 		$output = ob_get_clean();
-		$this->assertNotContains( '<p>', $output );
-		$this->assertNotContains( '<br />', $output );
+		$this->assertStringNotContainsString( '<p>', $output );
+		$this->assertStringNotContainsString( '<br />', $output );
 		$this->assertEmpty( $this->widget_text_content_args );
 		$this->assertNotEmpty( $this->widget_text_args );
-		$this->assertContains( '[filter:widget_text]', $output );
-		$this->assertNotContains( '[filter:widget_text_content]', $output );
+		$this->assertStringContainsString( '[filter:widget_text]', $output );
+		$this->assertStringNotContainsString( '[filter:widget_text_content]', $output );
 
 		// Test with filter=true, implicit legacy mode.
 		$this->widget_text_content_args = null;
@@ -170,15 +170,15 @@ class Test_WP_Widget_Text extends WP_UnitTestCase {
 		ob_start();
 		$widget->widget( $args, $instance );
 		$output = ob_get_clean();
-		$this->assertContains( '<p>', $output );
-		$this->assertContains( '<br />', $output );
+		$this->assertStringContainsString( '<p>', $output );
+		$this->assertStringContainsString( '<br />', $output );
 		$this->assertNotEmpty( $this->widget_text_args );
 		$this->assertSame( $instance['text'], $this->widget_text_args[0] );
 		$this->assertSame( $instance, $this->widget_text_args[1] );
 		$this->assertSame( $widget, $this->widget_text_args[2] );
 		$this->assertEmpty( $this->widget_text_content_args );
-		$this->assertContains( '[filter:widget_text]', $output );
-		$this->assertNotContains( '[filter:widget_text_content]', $output );
+		$this->assertStringContainsString( '[filter:widget_text]', $output );
+		$this->assertStringNotContainsString( '[filter:widget_text_content]', $output );
 
 		// Test with filter=content, the upgraded widget, in 4.8.0 only.
 		$this->widget_text_content_args = null;
@@ -197,8 +197,8 @@ class Test_WP_Widget_Text extends WP_UnitTestCase {
 		ob_start();
 		$widget->widget( $args, $instance );
 		$output = ob_get_clean();
-		$this->assertContains( '<p>', $output );
-		$this->assertContains( '<br />', $output );
+		$this->assertStringContainsString( '<p>', $output );
+		$this->assertStringContainsString( '<br />', $output );
 		$this->assertCount( 3, $this->widget_text_args );
 		$this->assertSame( $expected_instance['text'], $this->widget_text_args[0] );
 		$this->assertSame( $expected_instance, $this->widget_text_args[1] );
@@ -207,7 +207,7 @@ class Test_WP_Widget_Text extends WP_UnitTestCase {
 		$this->assertSame( $expected_instance['text'] . '[filter:widget_text]', $this->widget_text_content_args[0] );
 		$this->assertSame( $expected_instance, $this->widget_text_content_args[1] );
 		$this->assertSame( $widget, $this->widget_text_content_args[2] );
-		$this->assertContains( wpautop( $expected_instance['text'] . '[filter:widget_text][filter:widget_text_content]' ), $output );
+		$this->assertStringContainsString( wpautop( $expected_instance['text'] . '[filter:widget_text][filter:widget_text_content]' ), $output );
 
 		// Test with filter=true&visual=true, the upgraded widget, in 4.8.1 and above.
 		$this->widget_text_content_args = null;
@@ -221,8 +221,8 @@ class Test_WP_Widget_Text extends WP_UnitTestCase {
 		ob_start();
 		$widget->widget( $args, $instance );
 		$output = ob_get_clean();
-		$this->assertContains( '<p>', $output );
-		$this->assertContains( '<br />', $output );
+		$this->assertStringContainsString( '<p>', $output );
+		$this->assertStringContainsString( '<br />', $output );
 		$this->assertCount( 3, $this->widget_text_args );
 		$this->assertSame( $expected_instance['text'], $this->widget_text_args[0] );
 		$this->assertSame( $expected_instance, $this->widget_text_args[1] );
@@ -231,7 +231,7 @@ class Test_WP_Widget_Text extends WP_UnitTestCase {
 		$this->assertSame( $expected_instance['text'] . '[filter:widget_text]', $this->widget_text_content_args[0] );
 		$this->assertSame( $expected_instance, $this->widget_text_content_args[1] );
 		$this->assertSame( $widget, $this->widget_text_content_args[2] );
-		$this->assertContains( wpautop( $expected_instance['text'] . '[filter:widget_text][filter:widget_text_content]' ), $output );
+		$this->assertStringContainsString( wpautop( $expected_instance['text'] . '[filter:widget_text][filter:widget_text_content]' ), $output );
 
 		// Test with filter=true&visual=true, the upgraded widget, in 4.8.1 and above.
 		$this->widget_text_content_args = null;
@@ -245,14 +245,14 @@ class Test_WP_Widget_Text extends WP_UnitTestCase {
 		ob_start();
 		$widget->widget( $args, $instance );
 		$output = ob_get_clean();
-		$this->assertContains( '<p>', $output );
-		$this->assertContains( '<br />', $output );
+		$this->assertStringContainsString( '<p>', $output );
+		$this->assertStringContainsString( '<br />', $output );
 		$this->assertCount( 3, $this->widget_text_args );
 		$this->assertSame( $expected_instance['text'], $this->widget_text_args[0] );
 		$this->assertSame( $expected_instance, $this->widget_text_args[1] );
 		$this->assertSame( $widget, $this->widget_text_args[2] );
 		$this->assertNull( $this->widget_text_content_args );
-		$this->assertContains( wpautop( $expected_instance['text'] . '[filter:widget_text]' ), $output );
+		$this->assertStringContainsString( wpautop( $expected_instance['text'] . '[filter:widget_text]' ), $output );
 
 		// Test with filter=false&visual=false, the upgraded widget, in 4.8.1 and above.
 		$this->widget_text_content_args = null;
@@ -266,14 +266,14 @@ class Test_WP_Widget_Text extends WP_UnitTestCase {
 		ob_start();
 		$widget->widget( $args, $instance );
 		$output = ob_get_clean();
-		$this->assertNotContains( '<p>', $output );
-		$this->assertNotContains( '<br />', $output );
+		$this->assertStringNotContainsString( '<p>', $output );
+		$this->assertStringNotContainsString( '<br />', $output );
 		$this->assertCount( 3, $this->widget_text_args );
 		$this->assertSame( $expected_instance['text'], $this->widget_text_args[0] );
 		$this->assertSame( $expected_instance, $this->widget_text_args[1] );
 		$this->assertSame( $widget, $this->widget_text_args[2] );
 		$this->assertNull( $this->widget_text_content_args );
-		$this->assertContains( $expected_instance['text'] . '[filter:widget_text]', $output );
+		$this->assertStringContainsString( $expected_instance['text'] . '[filter:widget_text]', $output );
 	}
 
 	/**
@@ -345,9 +345,9 @@ class Test_WP_Widget_Text extends WP_UnitTestCase {
 		$widget->widget( $args, $instance );
 		$output = ob_get_clean();
 		$this->assertSame( 1, $this->shortcode_render_count );
-		$this->assertNotContains( '[example]', $output, 'Expected shortcode to be processed in legacy widget with plugin adding filter' );
-		$this->assertContains( $this->example_shortcode_content, $output, 'Shortcode was applied without wpautop corrupting it.' );
-		$this->assertNotContains( '<p>' . $this->example_shortcode_content . '</p>', $output, 'Expected shortcode_unautop() to have run.' );
+		$this->assertStringNotContainsString( '[example]', $output, 'Expected shortcode to be processed in legacy widget with plugin adding filter' );
+		$this->assertStringContainsString( $this->example_shortcode_content, $output, 'Shortcode was applied without wpautop corrupting it.' );
+		$this->assertStringNotContainsString( '<p>' . $this->example_shortcode_content . '</p>', $output, 'Expected shortcode_unautop() to have run.' );
 		$this->assertNull( $this->post_during_shortcode );
 
 		// Legacy Text Widget with wpautop().
@@ -363,9 +363,9 @@ class Test_WP_Widget_Text extends WP_UnitTestCase {
 		$widget->widget( $args, $instance );
 		$output = ob_get_clean();
 		$this->assertSame( 1, $this->shortcode_render_count );
-		$this->assertNotContains( '[example]', $output, 'Expected shortcode to be processed in legacy widget with plugin adding filter' );
-		$this->assertContains( $this->example_shortcode_content, $output, 'Shortcode was applied without wpautop corrupting it.' );
-		$this->assertNotContains( '<p>' . $this->example_shortcode_content . '</p>', $output, 'Expected shortcode_unautop() to have run.' );
+		$this->assertStringNotContainsString( '[example]', $output, 'Expected shortcode to be processed in legacy widget with plugin adding filter' );
+		$this->assertStringContainsString( $this->example_shortcode_content, $output, 'Shortcode was applied without wpautop corrupting it.' );
+		$this->assertStringNotContainsString( '<p>' . $this->example_shortcode_content . '</p>', $output, 'Expected shortcode_unautop() to have run.' );
 		$this->assertNull( $this->post_during_shortcode );
 
 		// Legacy text widget with plugin adding shortcode support as well.
@@ -375,8 +375,8 @@ class Test_WP_Widget_Text extends WP_UnitTestCase {
 		$widget->widget( $args, $instance );
 		$output = ob_get_clean();
 		$this->assertSame( 1, $this->shortcode_render_count );
-		$this->assertNotContains( '[example]', $output, 'Expected shortcode to be processed in legacy widget with plugin adding filter' );
-		$this->assertContains( wpautop( $this->example_shortcode_content ), $output, 'Shortcode was applied *with* wpautop() applying to shortcode output since plugin used legacy filter.' );
+		$this->assertStringNotContainsString( '[example]', $output, 'Expected shortcode to be processed in legacy widget with plugin adding filter' );
+		$this->assertStringContainsString( wpautop( $this->example_shortcode_content ), $output, 'Shortcode was applied *with* wpautop() applying to shortcode output since plugin used legacy filter.' );
 		$this->assertNull( $this->post_during_shortcode );
 		remove_filter( 'widget_text', 'do_shortcode' );
 
@@ -396,8 +396,8 @@ class Test_WP_Widget_Text extends WP_UnitTestCase {
 		$widget->widget( $args, $instance );
 		$output = ob_get_clean();
 		$this->assertSame( 1, $this->shortcode_render_count );
-		$this->assertContains( $this->example_shortcode_content, $output, 'Shortcode was applied without wpautop corrupting it.' );
-		$this->assertNotContains( '<p>' . $this->example_shortcode_content . '</p>', $output, 'Expected shortcode_unautop() to have run.' );
+		$this->assertStringContainsString( $this->example_shortcode_content, $output, 'Shortcode was applied without wpautop corrupting it.' );
+		$this->assertStringNotContainsString( '<p>' . $this->example_shortcode_content . '</p>', $output, 'Expected shortcode_unautop() to have run.' );
 		$this->assertFalse( has_filter( 'widget_text', 'do_shortcode' ), 'The widget_text filter still lacks do_shortcode handler.' );
 		$this->assertSame( 11, has_filter( 'widget_text_content', 'do_shortcode' ), 'The widget_text_content filter still has do_shortcode handler.' );
 		$this->assertNull( $this->post_during_shortcode );
@@ -409,8 +409,8 @@ class Test_WP_Widget_Text extends WP_UnitTestCase {
 		$widget->widget( $args, $instance );
 		$output = ob_get_clean();
 		$this->assertSame( 1, $this->shortcode_render_count );
-		$this->assertContains( $this->example_shortcode_content, $output, 'Shortcode was applied without wpautop corrupting it.' );
-		$this->assertNotContains( '<p>' . $this->example_shortcode_content . '</p>', $output, 'Expected shortcode_unautop() to have run.' );
+		$this->assertStringContainsString( $this->example_shortcode_content, $output, 'Shortcode was applied without wpautop corrupting it.' );
+		$this->assertStringNotContainsString( '<p>' . $this->example_shortcode_content . '</p>', $output, 'Expected shortcode_unautop() to have run.' );
 		$this->assertSame( 10, has_filter( 'widget_text', 'do_shortcode' ), 'Expected do_shortcode to be restored to widget_text.' );
 		$this->assertNull( $this->post_during_shortcode );
 		$this->assertNull( $this->post_during_shortcode );
@@ -424,8 +424,8 @@ class Test_WP_Widget_Text extends WP_UnitTestCase {
 		$widget->widget( $args, $instance );
 		$output = ob_get_clean();
 		$this->assertSame( 0, $this->shortcode_render_count );
-		$this->assertContains( '[example]', $output );
-		$this->assertNotContains( $this->example_shortcode_content, $output );
+		$this->assertStringContainsString( '[example]', $output );
+		$this->assertStringNotContainsString( $this->example_shortcode_content, $output );
 		$this->assertFalse( has_filter( 'widget_text', 'do_shortcode' ) );
 		$this->assertFalse( has_filter( 'widget_text_content', 'do_shortcode' ) );
 	}
@@ -644,8 +644,8 @@ class Test_WP_Widget_Text extends WP_UnitTestCase {
 		ob_start();
 		$widget->form( $instance );
 		$form = ob_get_clean();
-		$this->assertContains( 'class="visual" type="hidden" value=""', $form );
-		$this->assertNotContains( 'class="visual sync-input" type="hidden" value="on"', $form );
+		$this->assertStringContainsString( 'class="visual" type="hidden" value=""', $form );
+		$this->assertStringNotContainsString( 'class="visual sync-input" type="hidden" value="on"', $form );
 
 		$instance = array(
 			'title'  => 'Title',
@@ -656,8 +656,8 @@ class Test_WP_Widget_Text extends WP_UnitTestCase {
 		ob_start();
 		$widget->form( $instance );
 		$form = ob_get_clean();
-		$this->assertContains( 'class="visual sync-input" type="hidden" value="on"', $form );
-		$this->assertNotContains( 'class="visual sync-input" type="hidden" value=""', $form );
+		$this->assertStringContainsString( 'class="visual sync-input" type="hidden" value="on"', $form );
+		$this->assertStringNotContainsString( 'class="visual sync-input" type="hidden" value=""', $form );
 
 		$instance = array(
 			'title'  => 'Title',
@@ -668,8 +668,8 @@ class Test_WP_Widget_Text extends WP_UnitTestCase {
 		ob_start();
 		$widget->form( $instance );
 		$form = ob_get_clean();
-		$this->assertContains( 'class="visual sync-input" type="hidden" value="on"', $form );
-		$this->assertNotContains( 'class="visual sync-input" type="hidden" value=""', $form );
+		$this->assertStringContainsString( 'class="visual sync-input" type="hidden" value="on"', $form );
+		$this->assertStringNotContainsString( 'class="visual sync-input" type="hidden" value=""', $form );
 
 		$instance = array(
 			'title'  => 'Title',
@@ -681,9 +681,9 @@ class Test_WP_Widget_Text extends WP_UnitTestCase {
 		ob_start();
 		$widget->form( $instance );
 		$form = ob_get_clean();
-		$this->assertContains( 'class="visual sync-input" type="hidden" value="on"', $form );
-		$this->assertContains( '&lt;code&gt;&amp;lt;strong&amp;gt;BOLD!', $form );
-		$this->assertNotContains( 'class="visual sync-input" type="hidden" value=""', $form );
+		$this->assertStringContainsString( 'class="visual sync-input" type="hidden" value="on"', $form );
+		$this->assertStringContainsString( '&lt;code&gt;&amp;lt;strong&amp;gt;BOLD!', $form );
+		$this->assertStringNotContainsString( 'class="visual sync-input" type="hidden" value=""', $form );
 
 		remove_filter( 'user_can_richedit', '__return_true' );
 		add_filter( 'user_can_richedit', '__return_false' );
@@ -697,8 +697,8 @@ class Test_WP_Widget_Text extends WP_UnitTestCase {
 		ob_start();
 		$widget->form( $instance );
 		$form = ob_get_clean();
-		$this->assertNotContains( 'Evil:</textarea>', $form );
-		$this->assertContains( 'Evil:&lt;/textarea>', $form );
+		$this->assertStringNotContainsString( 'Evil:</textarea>', $form );
+		$this->assertStringContainsString( 'Evil:&lt;/textarea>', $form );
 	}
 
 	/**
@@ -999,7 +999,7 @@ class Test_WP_Widget_Text extends WP_UnitTestCase {
 		WP_Widget_Text::render_control_template_scripts();
 		$output = ob_get_clean();
 
-		$this->assertContains( '<script type="text/html" id="tmpl-widget-text-control-fields">', $output );
+		$this->assertStringContainsString( '<script type="text/html" id="tmpl-widget-text-control-fields">', $output );
 	}
 
 	/**
@@ -1026,7 +1026,7 @@ class Test_WP_Widget_Text extends WP_UnitTestCase {
 
 		$output = get_echo( array( $widget, 'widget' ), array( $args, $instance ) );
 
-		$this->assertContains( 'rel="noopener"', $output );
+		$this->assertStringContainsString( 'rel="noopener"', $output );
 	}
 
 	/**
@@ -1053,6 +1053,6 @@ class Test_WP_Widget_Text extends WP_UnitTestCase {
 
 		$output = get_echo( array( $widget, 'widget' ), array( $args, $instance ) );
 
-		$this->assertNotContains( 'rel="noopener"', $output );
+		$this->assertStringNotContainsString( 'rel="noopener"', $output );
 	}
 }
diff --git a/tests/phpunit/tests/widgets/wpWidgetRss.php b/tests/phpunit/tests/widgets/wpWidgetRss.php
index 65318423ff..d1625d4f62 100644
--- a/tests/phpunit/tests/widgets/wpWidgetRss.php
+++ b/tests/phpunit/tests/widgets/wpWidgetRss.php
@@ -87,7 +87,7 @@ class Test_Widgets_wpWidgetRss extends WP_UnitTestCase {
 		$widget->widget( $args, $instance );
 		$actual = ob_get_clean();
 
-		$this->assertContains( $expected, $actual );
+		$this->assertStringContainsString( $expected, $actual );
 	}
 
 	public function data_url_happy_path() {