diff --git a/tests/phpunit/data/themedir1/block-theme/theme.json b/tests/phpunit/data/themedir1/block-theme/theme.json
index 2c29884bf4dcb..4dca1dfb0ac2d 100644
--- a/tests/phpunit/data/themedir1/block-theme/theme.json
+++ b/tests/phpunit/data/themedir1/block-theme/theme.json
@@ -96,6 +96,11 @@
 						}
 					}
 				}
+			},
+			"my/unregistered-third-party-block": {
+				"color": {
+					"background": "hotpink"
+				}
 			}
 		},
 		"elements": {
diff --git a/tests/phpunit/tests/template.php b/tests/phpunit/tests/template.php
index a79702554dc64..00d64ae4d982e 100644
--- a/tests/phpunit/tests/template.php
+++ b/tests/phpunit/tests/template.php
@@ -151,6 +151,11 @@ public function tear_down() {
 			$registry->unregister( 'third-party/test' );
 		}
 
+		if ( isset( $GLOBALS['_wp_tests_development_mode'] ) ) {
+			remove_all_filters( 'theme_file_path' );
+			wp_theme_has_theme_json();
+		}
+
 		unset( $GLOBALS['_wp_tests_development_mode'] );
 		parent::tear_down();
 	}
diff --git a/tests/phpunit/tests/theme/support.php b/tests/phpunit/tests/theme/support.php
index aed9d94d3c1fd..d7262273e8536 100644
--- a/tests/phpunit/tests/theme/support.php
+++ b/tests/phpunit/tests/theme/support.php
@@ -41,6 +41,7 @@ public function test_post_thumbnails() {
 		$this->assertFalse( current_theme_supports( 'post-thumbnails' ) );
 		add_theme_support( 'post-thumbnails' );
 		$this->assertTrue( current_theme_supports( 'post-thumbnails' ) );
+		remove_theme_support( 'post-thumbnails' );
 	}
 
 	public function test_post_thumbnails_flat_array_of_post_types() {
@@ -57,6 +58,8 @@ public function test_post_thumbnails_flat_array_of_post_types() {
 	 * @ticket 22080
 	 */
 	public function test_post_thumbnails_mixed_args() {
+		remove_theme_support( 'post-thumbnails' );
+
 		add_theme_support( 'post-thumbnails', array( 'post', 'page' ) );
 		add_theme_support( 'post-thumbnails', array( 'page' ) );
 		$this->assertTrue( current_theme_supports( 'post-thumbnails', 'post' ) );
@@ -162,6 +165,8 @@ public function supports_foobar( $yesno, $args, $feature ) {
 	 * @ticket 11611
 	 */
 	public function test_plugin_hook() {
+		remove_theme_support( 'foobar' );
+
 		$this->assertFalse( current_theme_supports( 'foobar' ) );
 		add_theme_support( 'foobar' );
 		$this->assertTrue( current_theme_supports( 'foobar' ) );
@@ -185,6 +190,7 @@ public function test_plugin_hook_with_no_args() {
 		add_filter( 'current_theme_supports-foobar', '__return_false' );
 
 		$this->assertFalse( current_theme_supports( 'foobar' ) );
+		remove_theme_support( 'foobar' );
 	}
 
 	/**
diff --git a/tests/phpunit/tests/theme/wpAddGlobalStylesForBlocks.php b/tests/phpunit/tests/theme/wpAddGlobalStylesForBlocks.php
index b3a836dee704f..a7f8301971dd4 100644
--- a/tests/phpunit/tests/theme/wpAddGlobalStylesForBlocks.php
+++ b/tests/phpunit/tests/theme/wpAddGlobalStylesForBlocks.php
@@ -18,6 +18,13 @@ class Tests_Theme_WpAddGlobalStylesForBlocks extends WP_Theme_UnitTestCase {
 	 */
 	private $test_blocks = array();
 
+	/**
+	 * Original stylesheet.
+	 *
+	 * @var string
+	 */
+	private $original_stylesheet;
+
 	/**
 	 * Administrator ID.
 	 *
@@ -37,6 +44,7 @@ public static function set_up_before_class() {
 
 	public function set_up() {
 		parent::set_up();
+		$this->original_stylesheet = get_stylesheet();
 		remove_action( 'wp_print_styles', 'print_emoji_styles' );
 	}
 
@@ -49,6 +57,10 @@ public function tear_down() {
 			$this->test_blocks = array();
 		}
 
+		if ( get_stylesheet() !== $this->original_stylesheet ) {
+			switch_theme( $this->original_stylesheet );
+		}
+
 		parent::tear_down();
 	}
 
@@ -63,7 +75,7 @@ public function test_third_party_blocks_inline_styles_not_register_to_global_sty
 		wp_add_global_styles_for_blocks();
 
 		$this->assertNotContains(
-			':root :where(.wp-block-my-third-party-block){background-color: hotpink;}',
+			':root :where(.wp-block-my-unregistered-third-party-block){background-color: hotpink;}',
 			$this->get_global_styles()
 		);
 	}