diff --git a/tests/phpunit/includes/testcase-ajax.php b/tests/phpunit/includes/testcase-ajax.php
index e351ad2e49..34fd32a392 100644
--- a/tests/phpunit/includes/testcase-ajax.php
+++ b/tests/phpunit/includes/testcase-ajax.php
@@ -116,6 +116,8 @@ abstract class WP_Ajax_UnitTestCase extends WP_UnitTestCase {
 	);
 
 	public static function setUpBeforeClass() {
+		parent::setUpBeforeClass();
+
 		remove_action( 'admin_init', '_maybe_update_core' );
 		remove_action( 'admin_init', '_maybe_update_plugins' );
 		remove_action( 'admin_init', '_maybe_update_themes' );
@@ -126,8 +128,6 @@ abstract class WP_Ajax_UnitTestCase extends WP_UnitTestCase {
 				add_action( 'wp_ajax_' . $action, 'wp_ajax_' . str_replace( '-', '_', $action ), 1 );
 			}
 		}
-
-		parent::setUpBeforeClass();
 	}
 
 	/**
diff --git a/tests/phpunit/includes/testcase-block-supports.php b/tests/phpunit/includes/testcase-block-supports.php
index fbf6a1408d..f54dba8b9f 100644
--- a/tests/phpunit/includes/testcase-block-supports.php
+++ b/tests/phpunit/includes/testcase-block-supports.php
@@ -15,13 +15,6 @@ class Block_Supported_Styles_Test extends WP_UnitTestCase {
 	 */
 	private $registered_block_names = array();
 
-	/**
-	 * Sets up each test method.
-	 */
-	public function setUp() {
-		parent::setUp();
-	}
-
 	/**
 	 * Tear down each test method.
 	 */
diff --git a/tests/phpunit/tests/admin/includesScreen.php b/tests/phpunit/tests/admin/includesScreen.php
index ade4294c6b..09432dedca 100644
--- a/tests/phpunit/tests/admin/includesScreen.php
+++ b/tests/phpunit/tests/admin/includesScreen.php
@@ -156,8 +156,8 @@ class Tests_Admin_includesScreen extends WP_UnitTestCase {
 	);
 
 	function setUp() {
-		set_current_screen( 'front' );
 		parent::setUp();
+		set_current_screen( 'front' );
 	}
 
 	function tearDown() {
diff --git a/tests/phpunit/tests/adminbar.php b/tests/phpunit/tests/adminbar.php
index 1b54e5faf8..2004e30ae3 100644
--- a/tests/phpunit/tests/adminbar.php
+++ b/tests/phpunit/tests/adminbar.php
@@ -15,9 +15,9 @@ class Tests_AdminBar extends WP_UnitTestCase {
 	protected static $user_ids = array();
 
 	public static function setUpBeforeClass() {
-		require_once ABSPATH . WPINC . '/class-wp-admin-bar.php';
-
 		parent::setUpBeforeClass();
+
+		require_once ABSPATH . WPINC . '/class-wp-admin-bar.php';
 	}
 
 	public static function wpSetUpBeforeClass( WP_UnitTest_Factory $factory ) {
diff --git a/tests/phpunit/tests/comment/getCommentExcerpt.php b/tests/phpunit/tests/comment/getCommentExcerpt.php
index c79109cbe4..88c964a3ee 100644
--- a/tests/phpunit/tests/comment/getCommentExcerpt.php
+++ b/tests/phpunit/tests/comment/getCommentExcerpt.php
@@ -1,17 +1,11 @@
 <?php
 
 class Tests_Get_Comment_Excerpt extends WP_UnitTestCase {
-	protected static $bacon_comment;
-
-	public static function setUpBeforeClass() {
-		parent::setUpBeforeClass();
-
-		self::$bacon_comment = 'Bacon ipsum dolor amet porchetta capicola sirloin prosciutto brisket shankle jerky. Ham hock filet mignon boudin ground round, prosciutto alcatra spare ribs meatball turducken pork beef ribs ham beef. Bacon pastrami short loin, venison tri-tip ham short ribs doner swine. Tenderloin pig tongue pork jowl doner. Pork loin rump t-bone, beef strip steak flank drumstick tri-tip short loin capicola jowl. Cow filet mignon hamburger doner rump. Short loin jowl drumstick, tongue tail beef ribs pancetta flank brisket landjaeger chuck venison frankfurter turkey.
+	protected static $bacon_comment = 'Bacon ipsum dolor amet porchetta capicola sirloin prosciutto brisket shankle jerky. Ham hock filet mignon boudin ground round, prosciutto alcatra spare ribs meatball turducken pork beef ribs ham beef. Bacon pastrami short loin, venison tri-tip ham short ribs doner swine. Tenderloin pig tongue pork jowl doner. Pork loin rump t-bone, beef strip steak flank drumstick tri-tip short loin capicola jowl. Cow filet mignon hamburger doner rump. Short loin jowl drumstick, tongue tail beef ribs pancetta flank brisket landjaeger chuck venison frankfurter turkey.
 
 Brisket shank rump, tongue beef ribs swine fatback turducken capicola meatball picanha chicken cupim meatloaf turkey. Bacon biltong shoulder tail frankfurter boudin cupim turkey drumstick. Porchetta pig shoulder, jerky flank pork tail meatball hamburger. Doner ham hock ribeye tail jerky swine. Leberkas ribeye pancetta, tenderloin capicola doner turducken chicken venison ground round boudin pork chop. Tail pork loin pig spare ribs, biltong ribeye brisket pork chop cupim. Short loin leberkas spare ribs jowl landjaeger tongue kevin flank bacon prosciutto.
 
 Shankle pork chop prosciutto ribeye ham hock pastrami. T-bone shank brisket bacon pork chop. Cupim hamburger pork loin short loin. Boudin ball tip cupim ground round ham shoulder. Sausage rump cow tongue bresaola pork pancetta biltong tail chicken turkey hamburger. Kevin flank pork loin salami biltong. Alcatra landjaeger pastrami andouille kielbasa ham tenderloin drumstick sausage turducken tongue corned beef.';
-	}
 
 	public function test_get_comment_excerpt() {
 		$comment_id = self::factory()->comment->create(
diff --git a/tests/phpunit/tests/comment/query.php b/tests/phpunit/tests/comment/query.php
index 0a8a5ab6d7..e0dc8879e7 100644
--- a/tests/phpunit/tests/comment/query.php
+++ b/tests/phpunit/tests/comment/query.php
@@ -13,10 +13,6 @@ class Tests_Comment_Query extends WP_UnitTestCase {
 		self::$post_id = $factory->post->create();
 	}
 
-	function setUp() {
-		parent::setUp();
-	}
-
 	public function test_query() {
 		$c1 = self::factory()->comment->create(
 			array(
diff --git a/tests/phpunit/tests/dbdelta.php b/tests/phpunit/tests/dbdelta.php
index c54f9cc4dd..ae8d69c5ad 100644
--- a/tests/phpunit/tests/dbdelta.php
+++ b/tests/phpunit/tests/dbdelta.php
@@ -79,6 +79,8 @@ class Tests_dbDelta extends WP_UnitTestCase {
 			)
 		);
 
+		// This has to be called after the `CREATE TABLE` above as the `_create_temporary_tables` filter
+		// causes it to create a temporary table, and a temporary table cannot use a FULLTEXT index.
 		parent::setUp();
 	}
 
diff --git a/tests/phpunit/tests/feed/wp-simplepie-file.php b/tests/phpunit/tests/feed/wp-simplepie-file.php
index 260fa8a7eb..860181d397 100644
--- a/tests/phpunit/tests/feed/wp-simplepie-file.php
+++ b/tests/phpunit/tests/feed/wp-simplepie-file.php
@@ -17,6 +17,8 @@
  */
 class Tests_WP_SimplePie_File extends WP_UnitTestCase {
 	public static function setUpBeforeClass() {
+		parent::setUpBeforeClass();
+
 		require_once ABSPATH . '/wp-includes/class-simplepie.php';
 		require_once ABSPATH . '/wp-includes/class-wp-simplepie-file.php';
 	}
diff --git a/tests/phpunit/tests/image/editor.php b/tests/phpunit/tests/image/editor.php
index ee4b7dc525..47ee30a658 100644
--- a/tests/phpunit/tests/image/editor.php
+++ b/tests/phpunit/tests/image/editor.php
@@ -19,6 +19,7 @@ class Tests_Image_Editor extends WP_Image_UnitTestCase {
 
 		require_once DIR_TESTDATA . '/../includes/mock-image-editor.php';
 
+		// This needs to come after the mock image editor class is loaded.
 		parent::setUp();
 	}
 
diff --git a/tests/phpunit/tests/image/editorGd.php b/tests/phpunit/tests/image/editorGd.php
index f9d03e6149..2be19f93ef 100644
--- a/tests/phpunit/tests/image/editorGd.php
+++ b/tests/phpunit/tests/image/editorGd.php
@@ -17,6 +17,7 @@ class Tests_Image_Editor_GD extends WP_Image_UnitTestCase {
 		require_once ABSPATH . WPINC . '/class-wp-image-editor.php';
 		require_once ABSPATH . WPINC . '/class-wp-image-editor-gd.php';
 
+		// This needs to come after the mock image editor class is loaded.
 		parent::setUp();
 	}
 
diff --git a/tests/phpunit/tests/image/editorImagick.php b/tests/phpunit/tests/image/editorImagick.php
index a8bedce079..2d956e44a3 100644
--- a/tests/phpunit/tests/image/editorImagick.php
+++ b/tests/phpunit/tests/image/editorImagick.php
@@ -18,6 +18,7 @@ class Tests_Image_Editor_Imagick extends WP_Image_UnitTestCase {
 		require_once ABSPATH . WPINC . '/class-wp-image-editor-imagick.php';
 		require_once DIR_TESTROOT . '/includes/class-wp-test-stream.php';
 
+		// This needs to come after the mock image editor class is loaded.
 		parent::setUp();
 	}
 
diff --git a/tests/phpunit/tests/image/resizeGd.php b/tests/phpunit/tests/image/resizeGd.php
index fc39c9f7f6..55fd8b3bac 100644
--- a/tests/phpunit/tests/image/resizeGd.php
+++ b/tests/phpunit/tests/image/resizeGd.php
@@ -21,6 +21,7 @@ class Test_Image_Resize_GD extends WP_Tests_Image_Resize_UnitTestCase {
 		require_once ABSPATH . WPINC . '/class-wp-image-editor.php';
 		require_once ABSPATH . WPINC . '/class-wp-image-editor-gd.php';
 
+		// This needs to come after the mock image editor class is loaded.
 		parent::setUp();
 	}
 
diff --git a/tests/phpunit/tests/image/resizeImagick.php b/tests/phpunit/tests/image/resizeImagick.php
index ae402ee457..8a73572f42 100644
--- a/tests/phpunit/tests/image/resizeImagick.php
+++ b/tests/phpunit/tests/image/resizeImagick.php
@@ -21,6 +21,7 @@ class Test_Image_Resize_Imagick extends WP_Tests_Image_Resize_UnitTestCase {
 		require_once ABSPATH . WPINC . '/class-wp-image-editor.php';
 		require_once ABSPATH . WPINC . '/class-wp-image-editor-imagick.php';
 
+		// This needs to come after the mock image editor class is loaded.
 		parent::setUp();
 	}
 }
diff --git a/tests/phpunit/tests/menu/walker-nav-menu.php b/tests/phpunit/tests/menu/walker-nav-menu.php
index 9b63d63d54..1352b1d2ff 100644
--- a/tests/phpunit/tests/menu/walker-nav-menu.php
+++ b/tests/phpunit/tests/menu/walker-nav-menu.php
@@ -23,7 +23,6 @@ class Tests_Menu_Walker_Nav_Menu extends WP_UnitTestCase {
 		$this->walker = new Walker_Nav_Menu();
 
 		$this->_wp_nav_menu_max_depth = $_wp_nav_menu_max_depth;
-		parent::setUp();
 	}
 
 	/**
diff --git a/tests/phpunit/tests/menu/wpAjaxMenuQuickSearch.php b/tests/phpunit/tests/menu/wpAjaxMenuQuickSearch.php
index c78161d123..dda5845cc1 100644
--- a/tests/phpunit/tests/menu/wpAjaxMenuQuickSearch.php
+++ b/tests/phpunit/tests/menu/wpAjaxMenuQuickSearch.php
@@ -16,9 +16,10 @@ class Tests_Menu_WpAjaxMenuQuickSeach extends WP_UnitTestCase {
 	 * Set up. Workaround set_current_screen( null ) not working due to $hook_suffix not being set.
 	 */
 	function setUp() {
+		parent::setUp();
+
 		global $current_screen;
 		$this->current_screen = $current_screen;
-		parent::setUp();
 	}
 
 	/**
diff --git a/tests/phpunit/tests/post/formats.php b/tests/phpunit/tests/post/formats.php
index 44cedfc9a6..5fcd7dc1ff 100644
--- a/tests/phpunit/tests/post/formats.php
+++ b/tests/phpunit/tests/post/formats.php
@@ -4,10 +4,6 @@
  * @group post
  */
 class Tests_Post_Formats extends WP_UnitTestCase {
-	function setUp() {
-		parent::setUp();
-	}
-
 	function test_set_get_post_format_for_post() {
 		$post_id = self::factory()->post->create();
 
diff --git a/tests/phpunit/tests/post/getPages.php b/tests/phpunit/tests/post/getPages.php
index d1e88ffbd0..771de856b7 100644
--- a/tests/phpunit/tests/post/getPages.php
+++ b/tests/phpunit/tests/post/getPages.php
@@ -5,10 +5,6 @@
  */
 
 class Tests_Post_GetPages extends WP_UnitTestCase {
-	function setUp() {
-		parent::setUp();
-	}
-
 	/**
 	 * @ticket 23167
 	 */
diff --git a/tests/phpunit/tests/query/setupPostdata.php b/tests/phpunit/tests/query/setupPostdata.php
index 234bfdfa4d..a3183c3b25 100644
--- a/tests/phpunit/tests/query/setupPostdata.php
+++ b/tests/phpunit/tests/query/setupPostdata.php
@@ -11,20 +11,6 @@ class Tests_Query_SetupPostdata extends WP_UnitTestCase {
 
 	protected $pages_global;
 
-	public function setUp() {
-		parent::setUp();
-		return;
-
-		foreach ( $this->global_keys as $global_key ) {
-			if ( isset( $GLOBALS[ $global_key ] ) ) {
-				$this->global_data[ $global_key ] = $GLOBALS[ $global_key ];
-				unset( $GLOBALS[ $global_key ] );
-			} else {
-				$this->global_data[ $global_key ] = null;
-			}
-		}
-	}
-
 	public function test_id() {
 		$p = self::factory()->post->create_and_get();
 		setup_postdata( $p );
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 5106d0d502..06cf3a30ad 100644
--- a/tests/phpunit/tests/rest-api/rest-block-renderer-controller.php
+++ b/tests/phpunit/tests/rest-api/rest-block-renderer-controller.php
@@ -133,11 +133,12 @@ class REST_Block_Renderer_Controller_Test extends WP_Test_REST_Controller_Testca
 	 * @since 5.0.0
 	 */
 	public function setUp() {
+		parent::setUp();
+
 		$this->register_test_block();
 		$this->register_post_context_test_block();
 		$this->register_non_dynamic_block();
 		$this->register_dynamic_block_with_boolean_attributes();
-		parent::setUp();
 	}
 
 	/**
diff --git a/tests/phpunit/tests/upload.php b/tests/phpunit/tests/upload.php
index 43cd1e338a..4c8b73a8a1 100644
--- a/tests/phpunit/tests/upload.php
+++ b/tests/phpunit/tests/upload.php
@@ -8,8 +8,8 @@ class Tests_Upload extends WP_UnitTestCase {
 	public $siteurl;
 
 	function setUp() {
-		$this->_reset_options();
 		parent::setUp();
+		$this->_reset_options();
 	}
 
 	function _reset_options() {
diff --git a/tests/phpunit/tests/walker.php b/tests/phpunit/tests/walker.php
index c40db21a90..20b91df445 100644
--- a/tests/phpunit/tests/walker.php
+++ b/tests/phpunit/tests/walker.php
@@ -9,11 +9,9 @@
 class Tests_Walker extends WP_UnitTestCase {
 
 	function setUp() {
-
-		$this->walker = new Walker_Test();
-
 		parent::setUp();
 
+		$this->walker = new Walker_Test();
 	}
 
 	function test_single_item() {