diff --git a/tests/phpunit/tests/ajax/MediaEdit.php b/tests/phpunit/tests/ajax/MediaEdit.php
index 0060083820..aa6e6786a6 100644
--- a/tests/phpunit/tests/ajax/MediaEdit.php
+++ b/tests/phpunit/tests/ajax/MediaEdit.php
@@ -11,6 +11,8 @@ require_once ABSPATH . 'wp-admin/includes/ajax-actions.php';
  * @subpackage UnitTests
  * @since      3.5.0
  * @group      ajax
+ *
+ * @requires   function imagejpeg
  */
 class Tests_Ajax_MediaEdit extends WP_Ajax_UnitTestCase {
 
@@ -25,7 +27,6 @@ class Tests_Ajax_MediaEdit extends WP_Ajax_UnitTestCase {
 
 	/**
 	 * @ticket 22985
-	 * @requires function imagejpeg
 	 */
 	public function testCropImageThumbnail() {
 		require_once ABSPATH . 'wp-admin/includes/image-edit.php';
@@ -55,7 +56,6 @@ class Tests_Ajax_MediaEdit extends WP_Ajax_UnitTestCase {
 
 	/**
 	 * @ticket 32171
-	 * @requires function imagejpeg
 	 */
 	public function testImageEditOverwriteConstant() {
 		define( 'IMAGE_EDIT_OVERWRITE', true );
diff --git a/tests/phpunit/tests/cache.php b/tests/phpunit/tests/cache.php
index 79654fcaa9..0874bed8e1 100644
--- a/tests/phpunit/tests/cache.php
+++ b/tests/phpunit/tests/cache.php
@@ -251,7 +251,7 @@ class Tests_Cache extends WP_UnitTestCase {
 
 	function test_switch_to_blog() {
 		if ( ! method_exists( $this->cache, 'switch_to_blog' ) ) {
-			return;
+			$this->markTestSkipped( 'This test requires a switch_to_blog() method on the cache object.' );
 		}
 
 		$key  = __FUNCTION__;
diff --git a/tests/phpunit/tests/compat.php b/tests/phpunit/tests/compat.php
index cc6cf805e5..766b8fe545 100644
--- a/tests/phpunit/tests/compat.php
+++ b/tests/phpunit/tests/compat.php
@@ -242,12 +242,10 @@ EOT;
 	 * Test is_countable() polyfill for ResourceBundle.
 	 *
 	 * @ticket 43583
+	 *
+	 * @requires extension intl
 	 */
 	function test_is_countable_ResourceBundle() {
-		if ( ! class_exists( 'ResourceBundle' ) ) {
-			$this->markTestSkipped( 'The intl extension is not loaded. ResourceBundle not tested for is_countable().' );
-		}
-
 		$this->assertTrue( is_countable( new ResourceBundle( 'en', null ) ) );
 	}
 
@@ -255,12 +253,10 @@ EOT;
 	 * Test is_countable() polyfill for SimpleXMLElement.
 	 *
 	 * @ticket 43583
+	 *
+	 * @requires extension simplexml
 	 */
 	function test_is_countable_SimpleXMLElement() {
-		if ( ! class_exists( 'SimpleXMLElement' ) ) {
-			$this->markTestSkipped( 'The xml extension is not loaded. SimpleXMLElement not tested for is_countable().' );
-		}
-
 		$this->assertTrue( is_countable( new SimpleXMLElement( '<xml><tag>1</tag><tag>2</tag></xml>' ) ) );
 	}
 
diff --git a/tests/phpunit/tests/customize/manager.php b/tests/phpunit/tests/customize/manager.php
index a2a0365f24..8ae0c5d138 100644
--- a/tests/phpunit/tests/customize/manager.php
+++ b/tests/phpunit/tests/customize/manager.php
@@ -541,6 +541,7 @@ class Tests_WP_Customize_Manager extends WP_UnitTestCase {
 	 *
 	 * @covers WP_Customize_Manager::import_theme_starter_content
 	 * @covers WP_Customize_Manager::_save_starter_content_changeset
+	 * @requires function imagejpeg
 	 */
 	function test_import_theme_starter_content() {
 		wp_set_current_user( self::$admin_user_id );
diff --git a/tests/phpunit/tests/db/charset.php b/tests/phpunit/tests/db/charset.php
index 97a2d8136f..ecb3b10edb 100644
--- a/tests/phpunit/tests/db/charset.php
+++ b/tests/phpunit/tests/db/charset.php
@@ -762,7 +762,6 @@ class Tests_DB_Charset extends WP_UnitTestCase {
 
 		if ( ! self::$_wpdb->has_cap( 'utf8mb4' ) && preg_match( '/utf8mb[34]/i', $create ) ) {
 			$this->markTestSkipped( "This version of MySQL doesn't support utf8mb4." );
-			return;
 		}
 
 		self::$_wpdb->query( $create );
@@ -804,7 +803,6 @@ class Tests_DB_Charset extends WP_UnitTestCase {
 
 		if ( ! self::$_wpdb->has_cap( 'utf8mb4' ) && preg_match( '/utf8mb[34]/i', $create ) ) {
 			$this->markTestSkipped( "This version of MySQL doesn't support utf8mb4." );
-			return;
 		}
 
 		self::$_wpdb->query( $create );
@@ -828,7 +826,6 @@ class Tests_DB_Charset extends WP_UnitTestCase {
 
 		if ( ! self::$_wpdb->has_cap( 'utf8mb4' ) && preg_match( '/utf8mb[34]/i', $create ) ) {
 			$this->markTestSkipped( "This version of MySQL doesn't support utf8mb4." );
-			return;
 		}
 
 		self::$_wpdb->is_mysql = false;
@@ -856,7 +853,6 @@ class Tests_DB_Charset extends WP_UnitTestCase {
 
 		if ( ! self::$_wpdb->has_cap( 'utf8mb4' ) && preg_match( '/utf8mb[34]/i', $create ) ) {
 			$this->markTestSkipped( "This version of MySQL doesn't support utf8mb4." );
-			return;
 		}
 
 		unset( self::$_wpdb->is_mysql );
@@ -917,7 +913,6 @@ class Tests_DB_Charset extends WP_UnitTestCase {
 
 		if ( ! self::$_wpdb->has_cap( 'utf8mb4' ) && preg_match( '/utf8mb[34]/i', $create ) ) {
 			$this->markTestSkipped( "This version of MySQL doesn't support utf8mb4." );
-			return;
 		}
 
 		self::$_wpdb->query( $create );
diff --git a/tests/phpunit/tests/functions/anonymization.php b/tests/phpunit/tests/functions/anonymization.php
index d8a941da34..9ca33b441e 100644
--- a/tests/phpunit/tests/functions/anonymization.php
+++ b/tests/phpunit/tests/functions/anonymization.php
@@ -25,8 +25,6 @@ class Tests_Functions_Anonymization extends WP_UnitTestCase {
 	 *
 	 * @ticket 41083
 	 * @ticket 43545
-	 * @requires function inet_ntop
-	 * @requires function inet_pton
 	 *
 	 * @param string $raw_ip          Raw IP address.
 	 * @param string $expected_result Expected result.
@@ -90,26 +88,6 @@ class Tests_Functions_Anonymization extends WP_UnitTestCase {
 				'1000:0000:0000:0000:0000:0000:0000:0001or=\"',
 				'::',
 			),
-			// Malformed string with valid IP substring. Sometimes proxies add things like this, or other arbitrary strings.
-			array(
-				'or=\"[1000:0000:0000:0000:0000:0000:0000:0001]:400',
-				'1000::',
-			),
-			// Malformed string with valid IP substring. Sometimes proxies add things like this, or other arbitrary strings.
-			array(
-				'or=\"[1000:0000:0000:0000:0000:0000:0000:0001]',
-				'1000::',
-			),
-			// Malformed string with valid IP substring. Sometimes proxies add things like this, or other arbitrary strings.
-			array(
-				'or=\"[1000:0000:0000:0000:0000:0000:0000:0001]400',
-				'1000::',
-			),
-			// Malformed string with valid IP substring. Sometimes proxies add things like this, or other arbitrary strings.
-			array(
-				'[1000:0000:0000:0000:0000:0000:0000:0001]:235\"or=',
-				'1000::',
-			),
 			// IPv4, no port.
 			array(
 				'10.20.30.45',
@@ -125,36 +103,16 @@ class Tests_Functions_Anonymization extends WP_UnitTestCase {
 				'10.20.30.45/24',
 				'10.20.30.0',
 			),
-			// IPv6, no port.
-			array(
-				'2a03:2880:2110:df07:face:b00c::1',
-				'2a03:2880:2110:df07::',
-			),
-			// IPv6, port.
-			array(
-				'[2a03:2880:2110:df07:face:b00c::1]:20000',
-				'2a03:2880:2110:df07::',
-			),
 			// IPv6, no port, reducible representation.
 			array(
 				'0000:0000:0000:0000:0000:0000:0000:0001',
 				'::',
 			),
-			// IPv6, no port, partially reducible representation.
-			array(
-				'1000:0000:0000:0000:0000:0000:0000:0001',
-				'1000::',
-			),
 			// IPv6, port, reducible representation.
 			array(
 				'[0000:0000:0000:0000:0000:0000:0000:0001]:1234',
 				'::',
 			),
-			// IPv6, port, partially reducible representation.
-			array(
-				'[1000:0000:0000:0000:0000:0000:0000:0001]:5678',
-				'1000::',
-			),
 			// IPv6, no port, reduced representation.
 			array(
 				'::',
@@ -195,6 +153,80 @@ class Tests_Functions_Anonymization extends WP_UnitTestCase {
 				'[::127.0.0.1]:30000',
 				'::ffff:127.0.0.0',
 			),
+		);
+	}
+
+	/**
+	 * Test that wp_privacy_anonymize_ip() properly anonymizes all possible IP address formats.
+	 *
+	 * @dataProvider data_wp_privacy_anonymize_ip_with_inet_dependency
+	 *
+	 * @ticket 41083
+	 * @ticket 43545
+	 * @requires function inet_ntop
+	 * @requires function inet_pton
+	 *
+	 * @param string $raw_ip          Raw IP address.
+	 * @param string $expected_result Expected result.
+	 */
+	public function test_wp_privacy_anonymize_ip_with_inet_dependency( $raw_ip, $expected_result ) {
+		$this->test_wp_privacy_anonymize_ip( $raw_ip, $expected_result );
+	}
+
+	/**
+	 * Provide test cases for `test_wp_privacy_anonymize_ip()`.
+	 *
+	 * @since 4.9.6 Moved from `Test_WP_Community_Events::data_get_unsafe_client_ip_anonymization()`.
+	 *
+	 * @return array {
+	 *     @type array {
+	 *         @string string $raw_ip          Raw IP address.
+	 *         @string string $expected_result Expected result.
+	 *     }
+	 * }
+	 */
+	public function data_wp_privacy_anonymize_ip_with_inet_dependency() {
+		return array(
+			// Malformed string with valid IP substring. Sometimes proxies add things like this, or other arbitrary strings.
+			array(
+				'or=\"[1000:0000:0000:0000:0000:0000:0000:0001]:400',
+				'1000::',
+			),
+			// Malformed string with valid IP substring. Sometimes proxies add things like this, or other arbitrary strings.
+			array(
+				'or=\"[1000:0000:0000:0000:0000:0000:0000:0001]',
+				'1000::',
+			),
+			// Malformed string with valid IP substring. Sometimes proxies add things like this, or other arbitrary strings.
+			array(
+				'or=\"[1000:0000:0000:0000:0000:0000:0000:0001]400',
+				'1000::',
+			),
+			// Malformed string with valid IP substring. Sometimes proxies add things like this, or other arbitrary strings.
+			array(
+				'[1000:0000:0000:0000:0000:0000:0000:0001]:235\"or=',
+				'1000::',
+			),
+			// IPv6, no port.
+			array(
+				'2a03:2880:2110:df07:face:b00c::1',
+				'2a03:2880:2110:df07::',
+			),
+			// IPv6, port.
+			array(
+				'[2a03:2880:2110:df07:face:b00c::1]:20000',
+				'2a03:2880:2110:df07::',
+			),
+			// IPv6, no port, partially reducible representation.
+			array(
+				'1000:0000:0000:0000:0000:0000:0000:0001',
+				'1000::',
+			),
+			// IPv6, port, partially reducible representation.
+			array(
+				'[1000:0000:0000:0000:0000:0000:0000:0001]:5678',
+				'1000::',
+			),
 			// IPv6 with reachability scope.
 			array(
 				'fe80::b059:65f4:e877:c40%16',
diff --git a/tests/phpunit/tests/general/template.php b/tests/phpunit/tests/general/template.php
index 49545adb90..03c543dfa5 100644
--- a/tests/phpunit/tests/general/template.php
+++ b/tests/phpunit/tests/general/template.php
@@ -35,6 +35,7 @@ class Tests_General_Template extends WP_UnitTestCase {
 	/**
 	 * @group site_icon
 	 * @covers ::get_site_icon_url
+	 * @requires function imagejpeg
 	 */
 	function test_get_site_icon_url() {
 		$this->assertEmpty( get_site_icon_url() );
@@ -49,6 +50,7 @@ class Tests_General_Template extends WP_UnitTestCase {
 	/**
 	 * @group site_icon
 	 * @covers ::site_icon_url
+	 * @requires function imagejpeg
 	 */
 	function test_site_icon_url() {
 		$this->expectOutputString( '' );
@@ -62,6 +64,7 @@ class Tests_General_Template extends WP_UnitTestCase {
 	/**
 	 * @group site_icon
 	 * @covers ::has_site_icon
+	 * @requires function imagejpeg
 	 */
 	function test_has_site_icon() {
 		$this->assertFalse( has_site_icon() );
@@ -103,6 +106,7 @@ class Tests_General_Template extends WP_UnitTestCase {
 	/**
 	 * @group site_icon
 	 * @covers ::wp_site_icon
+	 * @requires function imagejpeg
 	 */
 	function test_wp_site_icon() {
 		$this->expectOutputString( '' );
@@ -125,6 +129,7 @@ class Tests_General_Template extends WP_UnitTestCase {
 	/**
 	 * @group site_icon
 	 * @covers ::wp_site_icon
+	 * @requires function imagejpeg
 	 */
 	function test_wp_site_icon_with_filter() {
 		$this->expectOutputString( '' );
diff --git a/tests/phpunit/tests/http/base.php b/tests/phpunit/tests/http/base.php
index c192065dbf..14aa731cec 100644
--- a/tests/phpunit/tests/http/base.php
+++ b/tests/phpunit/tests/http/base.php
@@ -20,11 +20,6 @@ abstract class WP_HTTP_UnitTestCase extends WP_UnitTestCase {
 	function setUp() {
 		parent::setUp();
 
-		if ( is_callable( array( 'WP_Http', '_getTransport' ) ) ) {
-			$this->markTestSkipped( 'The WP_Http tests require a class-http.php file of r17550 or later.' );
-			return;
-		}
-
 		$class = 'WP_Http_' . ucfirst( $this->transport );
 		if ( ! call_user_func( array( $class, 'test' ) ) ) {
 			$this->markTestSkipped( sprintf( 'The transport %s is not supported on this system.', $this->transport ) );
diff --git a/tests/phpunit/tests/http/functions.php b/tests/phpunit/tests/http/functions.php
index 05500cc407..c31803dead 100644
--- a/tests/phpunit/tests/http/functions.php
+++ b/tests/phpunit/tests/http/functions.php
@@ -3,7 +3,6 @@
 /**
  * @group http
  * @group external-http
- * @requires extension openssl
  */
 class Tests_HTTP_Functions extends WP_UnitTestCase {
 
diff --git a/tests/phpunit/tests/image/editorGd.php b/tests/phpunit/tests/image/editorGd.php
index d2523f4c6f..ed26316503 100644
--- a/tests/phpunit/tests/image/editorGd.php
+++ b/tests/phpunit/tests/image/editorGd.php
@@ -53,6 +53,8 @@ class Tests_Image_Editor_GD extends WP_Image_UnitTestCase {
 
 	/**
 	 * Test resizing an image, not using crop
+	 *
+	 * @requires function imagejpeg
 	 */
 	public function test_resize() {
 		$file = DIR_TESTDATA . '/images/waffles.jpg';
@@ -73,6 +75,8 @@ class Tests_Image_Editor_GD extends WP_Image_UnitTestCase {
 
 	/**
 	 * Test multi_resize with single image resize and no crop
+	 *
+	 * @requires function imagejpeg
 	 */
 	public function test_single_multi_resize() {
 		$file = DIR_TESTDATA . '/images/waffles.jpg';
@@ -183,6 +187,7 @@ class Tests_Image_Editor_GD extends WP_Image_UnitTestCase {
 	 * Test multi_resize with multiple sizes
 	 *
 	 * @ticket 26823
+	 * @requires function imagejpeg
 	 */
 	public function test_multi_resize() {
 		$file = DIR_TESTDATA . '/images/waffles.jpg';
diff --git a/tests/phpunit/tests/image/functions.php b/tests/phpunit/tests/image/functions.php
index 3f79070b09..204a79a648 100644
--- a/tests/phpunit/tests/image/functions.php
+++ b/tests/phpunit/tests/image/functions.php
@@ -172,18 +172,7 @@ class Tests_Image_Functions extends WP_UnitTestCase {
 	 * @requires extension fileinfo
 	 */
 	public function test_wp_save_image_file() {
-		$classes = array( 'WP_Image_Editor_GD', 'WP_Image_Editor_Imagick' );
-
-		foreach ( $classes as $key => $class ) {
-			if ( ! call_user_func( array( $class, 'test' ) ) ) {
-				// If the image editor isn't available, skip it.
-				unset( $classes[ $key ] );
-			}
-		}
-
-		if ( ! $classes ) {
-			$this->markTestSkipped( sprintf( 'The image editor engine %s is not supported on this system.', 'WP_Image_Editor_GD' ) );
-		}
+		$classes = $this->get_image_editor_engine_classes();
 
 		require_once ABSPATH . 'wp-admin/includes/image-edit.php';
 
@@ -233,18 +222,7 @@ class Tests_Image_Functions extends WP_UnitTestCase {
 	 * @requires extension fileinfo
 	 */
 	public function test_mime_overrides_filename() {
-		$classes = array( 'WP_Image_Editor_GD', 'WP_Image_Editor_Imagick' );
-
-		foreach ( $classes as $key => $class ) {
-			if ( ! call_user_func( array( $class, 'test' ) ) ) {
-				// If the image editor isn't available, skip it.
-				unset( $classes[ $key ] );
-			}
-		}
-
-		if ( ! $classes ) {
-			$this->markTestSkipped( sprintf( 'The image editor engine %s is not supported on this system.', 'WP_Image_Editor_GD' ) );
-		}
+		$classes = $this->get_image_editor_engine_classes();
 
 		// Test each image editor engine.
 		foreach ( $classes as $class ) {
@@ -275,18 +253,7 @@ class Tests_Image_Functions extends WP_UnitTestCase {
 	 * @requires extension fileinfo
 	 */
 	public function test_inferred_mime_types() {
-		$classes = array( 'WP_Image_Editor_GD', 'WP_Image_Editor_Imagick' );
-
-		foreach ( $classes as $key => $class ) {
-			if ( ! call_user_func( array( $class, 'test' ) ) ) {
-				// If the image editor isn't available, skip it.
-				unset( $classes[ $key ] );
-			}
-		}
-
-		if ( ! $classes ) {
-			$this->markTestSkipped( sprintf( 'The image editor engine %s is not supported on this system.', 'WP_Image_Editor_GD' ) );
-		}
+		$classes = $this->get_image_editor_engine_classes();
 
 		// Mime types.
 		$mime_types = array(
@@ -342,18 +309,7 @@ class Tests_Image_Functions extends WP_UnitTestCase {
 		$editor2 = wp_get_image_editor( DIR_TESTDATA );
 		$this->assertInstanceOf( 'WP_Error', $editor2 );
 
-		$classes = array( 'WP_Image_Editor_GD', 'WP_Image_Editor_Imagick' );
-
-		foreach ( $classes as $key => $class ) {
-			if ( ! call_user_func( array( $class, 'test' ) ) ) {
-				// If the image editor isn't available, skip it.
-				unset( $classes[ $key ] );
-			}
-		}
-
-		if ( ! $classes ) {
-			$this->markTestSkipped( sprintf( 'The image editor engine %s is not supported on this system.', 'WP_Image_Editor_GD' ) );
-		}
+		$classes = $this->get_image_editor_engine_classes();
 
 		// Then, test with editors.
 		foreach ( $classes as $class ) {
@@ -365,6 +321,28 @@ class Tests_Image_Functions extends WP_UnitTestCase {
 		}
 	}
 
+	/**
+	 * Get the available image editor engine class(es).
+	 *
+	 * @return string[] Available image editor classes; empty array when none are avaialble.
+	 */
+	private function get_image_editor_engine_classes() {
+		$classes = array( 'WP_Image_Editor_GD', 'WP_Image_Editor_Imagick' );
+
+		foreach ( $classes as $key => $class ) {
+			if ( ! call_user_func( array( $class, 'test' ) ) ) {
+				// If the image editor isn't available, skip it.
+				unset( $classes[ $key ] );
+			}
+		}
+
+		if ( empty( $classes ) ) {
+			$this->markTestSkipped( 'Image editor engines WP_Image_Editor_GD and WP_Image_Editor_Imagick are not supported on this system.' );
+		}
+
+		return $classes;
+	}
+
 	/**
 	 * @requires function imagejpeg
 	 */
diff --git a/tests/phpunit/tests/image/intermediateSize.php b/tests/phpunit/tests/image/intermediateSize.php
index 9b0e651c82..122971a069 100644
--- a/tests/phpunit/tests/image/intermediateSize.php
+++ b/tests/phpunit/tests/image/intermediateSize.php
@@ -156,6 +156,7 @@ class Tests_Image_Intermediate_Size extends WP_UnitTestCase {
 
 	/**
 	 * @ticket 17626
+	 * @requires function imagejpeg
 	 */
 	function test_get_intermediate_sizes_by_array_nearest_false() {
 		// If an exact size is not found, it should be returned.
diff --git a/tests/phpunit/tests/image/resizeGd.php b/tests/phpunit/tests/image/resizeGd.php
index 55fd8b3bac..171bc3f30a 100644
--- a/tests/phpunit/tests/image/resizeGd.php
+++ b/tests/phpunit/tests/image/resizeGd.php
@@ -5,6 +5,8 @@
  * @group media
  * @group upload
  * @group resize
+ *
+ * @requires function imagejpeg
  */
 require_once __DIR__ . '/resize.php';
 
diff --git a/tests/phpunit/tests/l10n/getLocale.php b/tests/phpunit/tests/l10n/getLocale.php
index 391ad08ed7..5a212019b9 100644
--- a/tests/phpunit/tests/l10n/getLocale.php
+++ b/tests/phpunit/tests/l10n/getLocale.php
@@ -39,7 +39,7 @@ class Tests_L10n_GetLocale extends WP_UnitTestCase {
 	 */
 	public function test_network_option_should_be_fallback_on_multisite() {
 		if ( ! is_multisite() ) {
-			$this->markTestSkipped( __METHOD__ . ' requires Multisite.' );
+			$this->markTestSkipped( 'This test requires Multisite.' );
 		}
 
 		global $locale;
@@ -59,7 +59,7 @@ class Tests_L10n_GetLocale extends WP_UnitTestCase {
 	 */
 	public function test_option_should_be_respected_on_nonmultisite() {
 		if ( is_multisite() ) {
-			$this->markTestSkipped( __METHOD__ . ' does not apply to Multisite.' );
+			$this->markTestSkipped( 'This test does not apply to Multisite.' );
 		}
 
 		global $locale;
diff --git a/tests/phpunit/tests/l10n/getUserLocale.php b/tests/phpunit/tests/l10n/getUserLocale.php
index f1d6f3828a..35f46b2454 100644
--- a/tests/phpunit/tests/l10n/getUserLocale.php
+++ b/tests/phpunit/tests/l10n/getUserLocale.php
@@ -72,7 +72,7 @@ class Tests_L10n_GetUserLocale extends WP_UnitTestCase {
 	 */
 	public function test_user_locale_is_same_across_network() {
 		if ( ! is_multisite() ) {
-			$this->markTestSkipped( __METHOD__ . ' requires Multisite.' );
+			$this->markTestSkipped( 'This test requires Multisite.' );
 		}
 
 		$user_locale = get_user_locale();
diff --git a/tests/phpunit/tests/media.php b/tests/phpunit/tests/media.php
index 816ba75b51..5c9512cd0a 100644
--- a/tests/phpunit/tests/media.php
+++ b/tests/phpunit/tests/media.php
@@ -1722,6 +1722,7 @@ EOF;
 
 	/**
 	 * @ticket 33641
+	 * @requires function imagejpeg
 	 */
 	function test_wp_calculate_image_srcset_no_width() {
 		$file       = get_attached_file( self::$large_id );
diff --git a/tests/phpunit/tests/pomo/mo.php b/tests/phpunit/tests/pomo/mo.php
index 8539e5e431..92d8cd21fb 100644
--- a/tests/phpunit/tests/pomo/mo.php
+++ b/tests/phpunit/tests/pomo/mo.php
@@ -179,7 +179,7 @@ class Tests_POMO_MO extends WP_UnitTestCase {
 
 	function test_overloaded_mb_functions() {
 		if ( ( ini_get( 'mbstring.func_overload' ) & 2 ) === 0 ) {
-			$this->markTestSkipped( __METHOD__ . ' only runs when mbstring.func_overload is enabled.' );
+			$this->markTestSkipped( 'This test requires mbstring.func_overload to be enabled.' );
 		}
 
 		$mo = new MO();
diff --git a/tests/phpunit/tests/rest-api/rest-attachments-controller.php b/tests/phpunit/tests/rest-api/rest-attachments-controller.php
index fab7c48a71..a2f7087528 100644
--- a/tests/phpunit/tests/rest-api/rest-attachments-controller.php
+++ b/tests/phpunit/tests/rest-api/rest-attachments-controller.php
@@ -743,6 +743,9 @@ class WP_Test_REST_Attachments_Controller extends WP_Test_REST_Post_Type_Control
 		$this->assertErrorResponse( 'rest_forbidden', $response, 401 );
 	}
 
+	/**
+	 * @requires function imagejpeg
+	 */
 	public function test_create_item() {
 		wp_set_current_user( self::$author_id );
 
@@ -792,6 +795,9 @@ class WP_Test_REST_Attachments_Controller extends WP_Test_REST_Post_Type_Control
 		$this->assertSame( 'codeispoetry', $data['title']['raw'] );
 	}
 
+	/**
+	 * @requires function imagejpeg
+	 */
 	public function test_create_item_with_files() {
 		wp_set_current_user( self::$author_id );
 		$request = new WP_REST_Request( 'POST', '/wp/v2/media' );
@@ -810,6 +816,9 @@ class WP_Test_REST_Attachments_Controller extends WP_Test_REST_Post_Type_Control
 		$this->assertSame( 201, $response->get_status() );
 	}
 
+	/**
+	 * @requires function imagejpeg
+	 */
 	public function test_create_item_with_upload_files_role() {
 		wp_set_current_user( self::$uploader_id );
 		$request = new WP_REST_Request( 'POST', '/wp/v2/media' );
@@ -924,6 +933,9 @@ class WP_Test_REST_Attachments_Controller extends WP_Test_REST_Post_Type_Control
 		$this->assertErrorResponse( 'rest_invalid_param', $response, 400 );
 	}
 
+	/**
+	 * @requires function imagejpeg
+	 */
 	public function test_create_item_alt_text() {
 		wp_set_current_user( self::$author_id );
 		$request = new WP_REST_Request( 'POST', '/wp/v2/media' );
@@ -937,6 +949,9 @@ class WP_Test_REST_Attachments_Controller extends WP_Test_REST_Post_Type_Control
 		$this->assertSame( 'test alt text', $attachment['alt_text'] );
 	}
 
+	/**
+	 * @requires function imagejpeg
+	 */
 	public function test_create_item_unsafe_alt_text() {
 		wp_set_current_user( self::$author_id );
 		$request = new WP_REST_Request( 'POST', '/wp/v2/media' );
@@ -951,6 +966,7 @@ class WP_Test_REST_Attachments_Controller extends WP_Test_REST_Post_Type_Control
 
 	/**
 	 * @ticket 40861
+	 * @requires function imagejpeg
 	 */
 	public function test_create_item_ensure_relative_path() {
 		wp_set_current_user( self::$author_id );
@@ -1274,6 +1290,7 @@ class WP_Test_REST_Attachments_Controller extends WP_Test_REST_Post_Type_Control
 
 	/**
 	 * @dataProvider attachment_roundtrip_provider
+	 * @requires function imagejpeg
 	 */
 	public function test_post_roundtrip_as_author( $raw, $expected ) {
 		wp_set_current_user( self::$author_id );
@@ -1281,6 +1298,9 @@ class WP_Test_REST_Attachments_Controller extends WP_Test_REST_Post_Type_Control
 		$this->verify_attachment_roundtrip( $raw, $expected );
 	}
 
+	/**
+	 * @requires function imagejpeg
+	 */
 	public function test_attachment_roundtrip_as_editor_unfiltered_html() {
 		wp_set_current_user( self::$editor_id );
 		if ( is_multisite() ) {
@@ -1332,6 +1352,9 @@ class WP_Test_REST_Attachments_Controller extends WP_Test_REST_Post_Type_Control
 		}
 	}
 
+	/**
+	 * @requires function imagejpeg
+	 */
 	public function test_attachment_roundtrip_as_superadmin_unfiltered_html() {
 		wp_set_current_user( self::$superadmin_id );
 		$this->assertTrue( current_user_can( 'unfiltered_html' ) );
@@ -1808,6 +1831,7 @@ class WP_Test_REST_Attachments_Controller extends WP_Test_REST_Post_Type_Control
 	 * once when attachments are created.
 	 *
 	 * @ticket 45269
+	 * @requires function imagejpeg
 	 */
 	public function test_rest_insert_attachment_hooks_fire_once_on_create() {
 		self::$rest_insert_attachment_count       = 0;
@@ -1865,6 +1889,7 @@ class WP_Test_REST_Attachments_Controller extends WP_Test_REST_Post_Type_Control
 
 	/**
 	 * @ticket 44567
+	 * @requires function imagejpeg
 	 */
 	public function test_create_item_with_meta_values() {
 		register_post_meta(
@@ -1902,6 +1927,7 @@ class WP_Test_REST_Attachments_Controller extends WP_Test_REST_Post_Type_Control
 
 	/**
 	 * @ticket 44405
+	 * @requires function imagejpeg
 	 */
 	public function test_edit_image_returns_error_if_logged_out() {
 		$attachment = self::factory()->attachment->create_upload_object( $this->test_file );
@@ -1914,6 +1940,7 @@ class WP_Test_REST_Attachments_Controller extends WP_Test_REST_Post_Type_Control
 
 	/**
 	 * @ticket 44405
+	 * @requires function imagejpeg
 	 */
 	public function test_edit_image_returns_error_if_cannot_upload() {
 		$user = self::factory()->user->create_and_get( array( 'role' => 'editor' ) );
@@ -1930,6 +1957,7 @@ class WP_Test_REST_Attachments_Controller extends WP_Test_REST_Post_Type_Control
 
 	/**
 	 * @ticket 44405
+	 * @requires function imagejpeg
 	 */
 	public function test_edit_image_returns_error_if_cannot_edit() {
 		wp_set_current_user( self::$uploader_id );
@@ -1956,6 +1984,7 @@ class WP_Test_REST_Attachments_Controller extends WP_Test_REST_Post_Type_Control
 
 	/**
 	 * @ticket 44405
+	 * @requires function imagejpeg
 	 */
 	public function test_edit_image_returns_error_if_unsupported_mime_type() {
 		wp_set_current_user( self::$superadmin_id );
@@ -1975,6 +2004,7 @@ class WP_Test_REST_Attachments_Controller extends WP_Test_REST_Post_Type_Control
 
 	/**
 	 * @ticket 44405
+	 * @requires function imagejpeg
 	 */
 	public function test_edit_image_returns_error_if_no_edits() {
 		wp_set_current_user( self::$superadmin_id );
@@ -1988,6 +2018,7 @@ class WP_Test_REST_Attachments_Controller extends WP_Test_REST_Post_Type_Control
 
 	/**
 	 * @ticket 44405
+	 * @requires function imagejpeg
 	 */
 	public function test_edit_image_rotate() {
 		wp_set_current_user( self::$superadmin_id );
@@ -2012,6 +2043,7 @@ class WP_Test_REST_Attachments_Controller extends WP_Test_REST_Post_Type_Control
 
 	/**
 	 * @ticket 44405
+	 * @requires function imagejpeg
 	 */
 	public function test_edit_image_crop() {
 		wp_set_current_user( self::$superadmin_id );
@@ -2118,6 +2150,7 @@ class WP_Test_REST_Attachments_Controller extends WP_Test_REST_Post_Type_Control
 
 	/**
 	 * @ticket 50565
+	 * @requires function imagejpeg
 	 */
 	public function test_edit_image_returns_error_if_mismatched_src() {
 		wp_set_current_user( self::$superadmin_id );
diff --git a/tests/phpunit/tests/url.php b/tests/phpunit/tests/url.php
index 67240a73b4..0386bde6fc 100644
--- a/tests/phpunit/tests/url.php
+++ b/tests/phpunit/tests/url.php
@@ -273,10 +273,6 @@ class Tests_URL extends WP_UnitTestCase {
 	}
 
 	function test_set_url_scheme() {
-		if ( ! function_exists( 'set_url_scheme' ) ) {
-			return;
-		}
-
 		$links = array(
 			'http://wordpress.org/',
 			'https://wordpress.org/',
diff --git a/tests/phpunit/tests/widgets/media-gallery-widget.php b/tests/phpunit/tests/widgets/media-gallery-widget.php
index d3ca909bcb..1e67497833 100644
--- a/tests/phpunit/tests/widgets/media-gallery-widget.php
+++ b/tests/phpunit/tests/widgets/media-gallery-widget.php
@@ -52,6 +52,7 @@ class Test_WP_Widget_Media_Gallery extends WP_UnitTestCase {
 	 * Test update() method.
 	 *
 	 * @covers WP_Widget_Media_Gallery::render_media
+	 * @requires function imagejpeg
 	 */
 	public function test_render_media() {
 		$widget = new WP_Widget_Media_Gallery();
diff --git a/tests/phpunit/tests/widgets/media-widget.php b/tests/phpunit/tests/widgets/media-widget.php
index 3877994ea3..ebe150d4f9 100644
--- a/tests/phpunit/tests/widgets/media-widget.php
+++ b/tests/phpunit/tests/widgets/media-widget.php
@@ -95,11 +95,8 @@ class Test_WP_Widget_Media extends WP_UnitTestCase {
 		$this->assertSame( $id_base, $widget->id_base );
 		$this->assertSame( $name, $widget->name );
 
-		// Method assertArraySubset doesn't exist in phpunit versions compatible with PHP 5.2.
-		if ( method_exists( $this, 'assertArraySubset' ) ) {
-			$this->assertArraySubset( $widget_options, $widget->widget_options );
-			$this->assertArraySubset( $control_options, $widget->control_options );
-		}
+		$this->assertArraySubset( $widget_options, $widget->widget_options );
+		$this->assertArraySubset( $control_options, $widget->control_options );
 	}
 
 	/**
@@ -135,6 +132,7 @@ class Test_WP_Widget_Media extends WP_UnitTestCase {
 	 * Test is_attachment_with_mime_type method.
 	 *
 	 * @covers WP_Widget_Media::is_attachment_with_mime_type
+	 * @requires function imagejpeg
 	 */
 	function test_is_attachment_with_mime_type() {
 
diff --git a/tests/phpunit/tests/xmlrpc/mw/editPost.php b/tests/phpunit/tests/xmlrpc/mw/editPost.php
index 271ad36f56..b20ee4a5c3 100644
--- a/tests/phpunit/tests/xmlrpc/mw/editPost.php
+++ b/tests/phpunit/tests/xmlrpc/mw/editPost.php
@@ -132,6 +132,9 @@ class Tests_XMLRPC_mw_editPost extends WP_XMLRPC_UnitTestCase {
 		$this->assertEquals( $editor_id, $out->post_author );
 	}
 
+	/**
+	 * @requires function imagejpeg
+	 */
 	function test_post_thumbnail() {
 		add_theme_support( 'post-thumbnails' );
 
diff --git a/tests/phpunit/tests/xmlrpc/mw/getPost.php b/tests/phpunit/tests/xmlrpc/mw/getPost.php
index 989f5c2290..fcdcdb3597 100644
--- a/tests/phpunit/tests/xmlrpc/mw/getPost.php
+++ b/tests/phpunit/tests/xmlrpc/mw/getPost.php
@@ -89,6 +89,9 @@ class Tests_XMLRPC_mw_getPost extends WP_XMLRPC_UnitTestCase {
 		remove_theme_support( 'post-thumbnails' );
 	}
 
+	/**
+	 * @requires function imagejpeg
+	 */
 	function test_post_thumbnail() {
 		add_theme_support( 'post-thumbnails' );
 
diff --git a/tests/phpunit/tests/xmlrpc/mw/getRecentPosts.php b/tests/phpunit/tests/xmlrpc/mw/getRecentPosts.php
index e6b00e5e42..8f5d52bb53 100644
--- a/tests/phpunit/tests/xmlrpc/mw/getRecentPosts.php
+++ b/tests/phpunit/tests/xmlrpc/mw/getRecentPosts.php
@@ -94,6 +94,9 @@ class Tests_XMLRPC_mw_getRecentPosts extends WP_XMLRPC_UnitTestCase {
 		remove_theme_support( 'post-thumbnails' );
 	}
 
+	/**
+	 * @requires function imagejpeg
+	 */
 	function test_post_thumbnail() {
 		add_theme_support( 'post-thumbnails' );
 
diff --git a/tests/phpunit/tests/xmlrpc/mw/newPost.php b/tests/phpunit/tests/xmlrpc/mw/newPost.php
index 456acbd31e..fcce8d0e66 100644
--- a/tests/phpunit/tests/xmlrpc/mw/newPost.php
+++ b/tests/phpunit/tests/xmlrpc/mw/newPost.php
@@ -128,6 +128,9 @@ class Tests_XMLRPC_mw_newPost extends WP_XMLRPC_UnitTestCase {
 		$this->assertSame( 'Test', $out->post_title );
 	}
 
+	/**
+	 * @requires function imagejpeg
+	 */
 	function test_post_thumbnail() {
 		add_theme_support( 'post-thumbnails' );
 
diff --git a/tests/phpunit/tests/xmlrpc/wp/editPost.php b/tests/phpunit/tests/xmlrpc/wp/editPost.php
index 8d732b1e64..ab3223fb7f 100644
--- a/tests/phpunit/tests/xmlrpc/wp/editPost.php
+++ b/tests/phpunit/tests/xmlrpc/wp/editPost.php
@@ -132,6 +132,9 @@ class Tests_XMLRPC_wp_editPost extends WP_XMLRPC_UnitTestCase {
 		$this->assertEquals( $editor_id, $out->post_author );
 	}
 
+	/**
+	 * @requires function imagejpeg
+	 */
 	function test_post_thumbnail() {
 		add_theme_support( 'post-thumbnails' );
 
diff --git a/tests/phpunit/tests/xmlrpc/wp/getMediaItem.php b/tests/phpunit/tests/xmlrpc/wp/getMediaItem.php
index 39f31726b9..41dd0300dc 100644
--- a/tests/phpunit/tests/xmlrpc/wp/getMediaItem.php
+++ b/tests/phpunit/tests/xmlrpc/wp/getMediaItem.php
@@ -2,6 +2,7 @@
 
 /**
  * @group xmlrpc
+ * @requires function imagejpeg
  */
 class Tests_XMLRPC_wp_getMediaItem extends WP_XMLRPC_UnitTestCase {
 	protected static $post_id;
diff --git a/tests/phpunit/tests/xmlrpc/wp/newPost.php b/tests/phpunit/tests/xmlrpc/wp/newPost.php
index 8fe16c12de..34afb87b77 100644
--- a/tests/phpunit/tests/xmlrpc/wp/newPost.php
+++ b/tests/phpunit/tests/xmlrpc/wp/newPost.php
@@ -145,6 +145,9 @@ class Tests_XMLRPC_wp_newPost extends WP_XMLRPC_UnitTestCase {
 		$this->assertSame( 'Test', $out->post_title );
 	}
 
+	/**
+	 * @requires function imagejpeg
+	 */
 	function test_post_thumbnail() {
 		add_theme_support( 'post-thumbnails' );
 
diff --git a/tests/phpunit/tests/xmlrpc/wp/uploadFile.php b/tests/phpunit/tests/xmlrpc/wp/uploadFile.php
index b9ba569a44..5098735bad 100644
--- a/tests/phpunit/tests/xmlrpc/wp/uploadFile.php
+++ b/tests/phpunit/tests/xmlrpc/wp/uploadFile.php
@@ -2,6 +2,7 @@
 
 /**
  * @group xmlrpc
+ * @requires function imagejpeg
  */
 class Tests_XMLRPC_wp_uploadFile extends WP_XMLRPC_UnitTestCase {