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() {