@@ -69,6 +69,7 @@ public static function set_up_before_class() {
 	public static function tear_down_after_class() {
 		// Reset static flags.
 		self::$requires_switch_theme_fixtures = false;
+		self::$theme_root                     = null;
 
 		parent::tear_down_after_class();
 	}
 
@@ -16,8 +16,9 @@ class Tests_Fonts_WpPrintFontFacesFromStyleVariations extends WP_Font_Face_UnitT
 	const FONTS_THEME = 'fonts-block-theme';
 
 	public static function set_up_before_class() {
-		parent::set_up_before_class();
 		self::$requires_switch_theme_fixtures = true;
+
+		parent::set_up_before_class();
 	}
 
 	/**
 
@@ -31,6 +31,20 @@ class REST_Block_Type_Controller_Test extends WP_Test_REST_Controller_Testcase {
 	 */
 	protected static $subscriber_id;
 
+	/**
+	 * Pre-existing block types registered before the current test.
+	 *
+	 * @var string[] $registered_block_types
+	 */
+	private $registered_block_types = array();
+
+	/**
+	 * Pre-existing block styles registered before the current test, grouped by block type name.
+	 *
+	 * @var array[] $registered_block_styles
+	 */
+	private $registered_block_styles = array();
+
 	/**
 	 * Create fake data before our tests run.
 	 *
@@ -49,21 +63,55 @@ public static function wpSetUpBeforeClass( WP_UnitTest_Factory $factory ) {
 				'role' => 'subscriber',
 			)
 		);
-
-		$name     = 'fake/test';
-		$settings = array(
-			'icon' => 'text',
-		);
-
-		register_block_type( $name, $settings );
 	}
 
 	public static function wpTearDownAfterClass() {
 		self::delete_user( self::$admin_id );
 		self::delete_user( self::$subscriber_id );
-		unregister_block_type( 'fake/test' );
-		unregister_block_type( 'fake/invalid' );
-		unregister_block_type( 'fake/false' );
+	}
+
+	/**
+	 * Sets up each test method.
+	 *
+	 * Records the registered block types and block styles so that anything
+	 * registered by a test can be unregistered again in tear_down(), and
+	 * registers a block type used by many tests in this class.
+	 */
+	public function set_up() {
+		parent::set_up();
+
+		$this->registered_block_types  = array_keys( WP_Block_Type_Registry::get_instance()->get_all_registered() );
+		$this->registered_block_styles = WP_Block_Styles_Registry::get_instance()->get_all_registered();
+
+		register_block_type(
+			'fake/test',
+			array(
+				'icon' => 'text',
+			)
+		);
+	}
+
+	/**
+	 * Tears down each test method.
+	 *
+	 * Unregisters any block types and block styles registered while the test ran.
+	 */
+	public function tear_down() {
+		foreach ( WP_Block_Styles_Registry::get_instance()->get_all_registered() as $block_name => $block_styles ) {
+			foreach ( array_keys( $block_styles ) as $block_style_name ) {
+				if ( ! isset( $this->registered_block_styles[ $block_name ][ $block_style_name ] ) ) {
+					unregister_block_style( $block_name, $block_style_name );
+				}
+			}
+		}
+
+		foreach ( array_keys( WP_Block_Type_Registry::get_instance()->get_all_registered() ) as $block_name ) {
+			if ( ! in_array( $block_name, $this->registered_block_types, true ) ) {
+				unregister_block_type( $block_name );
+			}
+		}
+
+		parent::tear_down();
 	}
 
 	/**
 
@@ -464,15 +464,17 @@ public function test_sitemaps_enabled() {
 
 	/**
 	 * @ticket 50643
-	 * @runInSeparateProcess
-	 * @preserveGlobalState disabled
 	 */
 	public function test_disable_sitemap_should_return_404() {
 		add_filter( 'wp_sitemaps_enabled', '__return_false' );
 
+		// Instantiate the server before navigating: registering the sitemap
+		// rewrite tags is what adds `sitemap` to `$wp->public_query_vars`.
+		$sitemaps = wp_sitemaps_get_server();
+
 		$this->go_to( home_url( '/?sitemap=index' ) );
 
-		wp_sitemaps_get_server()->render_sitemaps();
+		$sitemaps->render_sitemaps();
 
 		remove_filter( 'wp_sitemaps_enabled', '__return_false' );
 
@@ -481,8 +483,6 @@ public function test_disable_sitemap_should_return_404() {
 
 	/**
 	 * @ticket 50643
-	 * @runInSeparateProcess
-	 * @preserveGlobalState disabled
 	 */
 	public function test_empty_url_list_should_return_404() {
 		wp_register_sitemap_provider( 'foo', new WP_Sitemaps_Empty_Test_Provider( 'foo' ) );
 
@@ -316,6 +316,9 @@ public function test_enqueue_admin_scripts() {
 	 * @covers WP_Widget_Media_Audio::render_control_template_scripts
 	 */
 	public function test_render_control_template_scripts() {
+		// Provides wp_underscore_audio_template(), normally loaded by wp_enqueue_media().
+		require_once ABSPATH . WPINC . '/media-template.php';
+
 		$widget = new WP_Widget_Media_Audio();
 
 		ob_start();
 
@@ -344,6 +344,9 @@ public function test_enqueue_admin_scripts() {
 	 * @covers WP_Widget_Media_Video::render_control_template_scripts
 	 */
 	public function test_render_control_template_scripts() {
+		// Provides wp_underscore_video_template(), normally loaded by wp_enqueue_media().
+		require_once ABSPATH . WPINC . '/media-template.php';
+
 		$widget = new WP_Widget_Media_Video();
 
 		ob_start();
Original file line number	Diff line number	Diff line change
`@@ -69,6 +69,7 @@ public static function set_up_before_class() {`
`69`	`69`	`public static function tear_down_after_class() {`
`70`	`70`	`// Reset static flags.`
`71`	`71`	`self::$requires_switch_theme_fixtures = false;`
	`72`	`+ self::$theme_root = null;`
`72`	`73`
`73`	`74`	`parent::tear_down_after_class();`
`74`	`75`	`}`
Original file line number	Diff line number	Diff line change
`@@ -16,8 +16,9 @@ class Tests_Fonts_WpPrintFontFacesFromStyleVariations extends WP_Font_Face_UnitT`
`16`	`16`	`const FONTS_THEME = 'fonts-block-theme';`
`17`	`17`
`18`	`18`	`public static function set_up_before_class() {`
`19`		`- parent::set_up_before_class();`
`20`	`19`	`self::$requires_switch_theme_fixtures = true;`
	`20`	`+`
	`21`	`+ parent::set_up_before_class();`
`21`	`22`	`}`
`22`	`23`
`23`	`24`	`/**`