diff --git a/tests/phpunit/includes/abstract-testcase.php b/tests/phpunit/includes/abstract-testcase.php
index c87e5e7fd077c..c94c944b39da1 100644
--- a/tests/phpunit/includes/abstract-testcase.php
+++ b/tests/phpunit/includes/abstract-testcase.php
@@ -25,6 +25,13 @@ abstract class WP_UnitTestCase_Base extends PHPUnit_Adapter_TestCase {
 	protected static $hooks_saved = array();
 	protected static $ignore_files;
 
+	/**
+	 * Site locale before each test.
+	 *
+	 * @var string
+	 */
+	protected $original_locale = 'en_US';
+
 	/**
 	 * Fixture factory.
 	 *
@@ -122,6 +129,14 @@ public function set_up() {
 
 		$this->clean_up_global_scope();
 
+		/*
+		 * Capture the site locale after resetting the runtime cache so it can be
+		 * restored without querying the database after the test transaction rolls back.
+		 */
+		unset( $GLOBALS['locale'] );
+		$this->original_locale = determine_locale();
+		WP_Translation_Controller::get_instance()->set_locale( $this->original_locale );
+
 		/*
 		 * When running core tests, ensure that post types and taxonomies
 		 * are reset for each test. We skip this step for non-core tests,
@@ -229,7 +244,9 @@ public function tear_down() {
 		remove_filter( 'wp_die_handler', array( $this, 'get_wp_die_handler' ) );
 		$this->_restore_hooks();
 		wp_set_current_user( 0 );
-
+		// Synchronize the locale globals with the site locale captured before the test.
+		$GLOBALS['locale'] = $this->original_locale;
+		WP_Translation_Controller::get_instance()->set_locale( $this->original_locale );
 		$this->reset_lazyload_queue();
 
 		WP_Style_Engine_CSS_Rules_Store::remove_all_stores();
diff --git a/tests/phpunit/tests/l10n/loadScriptTextdomain.php b/tests/phpunit/tests/l10n/loadScriptTextdomain.php
index b84527e1f1757..7ceb2e3d2cc5a 100644
--- a/tests/phpunit/tests/l10n/loadScriptTextdomain.php
+++ b/tests/phpunit/tests/l10n/loadScriptTextdomain.php
@@ -19,6 +19,8 @@ class Tests_L10n_LoadScriptTextdomain extends WP_UnitTestCase {
 	 * @dataProvider data_resolve_relative_path
 	 */
 	public function test_resolve_relative_path( $translation_path, $handle, $src, $textdomain, $filter = array() ) {
+		wp_scripts();
+
 		if ( ! empty( $filter ) ) {
 			add_filter( $filter[0], $filter[1], 10, $filter[2] ?? 1 );
 		}
diff --git a/tests/phpunit/tests/privacy/wpPrivacySendErasureFulfillmentNotification.php b/tests/phpunit/tests/privacy/wpPrivacySendErasureFulfillmentNotification.php
index bb6195912e233..448e5be5a6b50 100644
--- a/tests/phpunit/tests/privacy/wpPrivacySendErasureFulfillmentNotification.php
+++ b/tests/phpunit/tests/privacy/wpPrivacySendErasureFulfillmentNotification.php
@@ -84,6 +84,10 @@ public static function wpSetUpBeforeClass( WP_UnitTest_Factory $factory ) {
 	 */
 	public function set_up() {
 		parent::set_up();
+
+		unset( $GLOBALS['locale'] );
+		get_locale();
+
 		reset_phpmailer_instance();
 	}
 
@@ -96,6 +100,8 @@ public function tear_down() {
 		reset_phpmailer_instance();
 		restore_previous_locale();
 		parent::tear_down();
+
+		unset( $GLOBALS['locale'] );
 	}
 
 	/**
diff --git a/tests/phpunit/tests/privacy/wpPrivacySendPersonalDataExportEmail.php b/tests/phpunit/tests/privacy/wpPrivacySendPersonalDataExportEmail.php
index 37e2e4c282bd5..036f9b2aefe74 100644
--- a/tests/phpunit/tests/privacy/wpPrivacySendPersonalDataExportEmail.php
+++ b/tests/phpunit/tests/privacy/wpPrivacySendPersonalDataExportEmail.php
@@ -80,6 +80,10 @@ public static function wpSetUpBeforeClass( WP_UnitTest_Factory $factory ) {
 	 */
 	public function set_up() {
 		parent::set_up();
+
+		unset( $GLOBALS['locale'] );
+		get_locale();
+
 		reset_phpmailer_instance();
 	}
 
@@ -92,6 +96,8 @@ public function tear_down() {
 		reset_phpmailer_instance();
 		restore_previous_locale();
 		parent::tear_down();
+
+		unset( $GLOBALS['locale'] );
 	}
 
 	/**
diff --git a/tests/phpunit/tests/user/wpSendUserRequest.php b/tests/phpunit/tests/user/wpSendUserRequest.php
index 11e3130f225a5..be73c1eaafbd3 100644
--- a/tests/phpunit/tests/user/wpSendUserRequest.php
+++ b/tests/phpunit/tests/user/wpSendUserRequest.php
@@ -60,6 +60,9 @@ public static function wpSetUpBeforeClass( WP_UnitTest_Factory $factory ) {
 	public function set_up() {
 		parent::set_up();
 
+		unset( $GLOBALS['locale'] );
+		get_locale();
+
 		set_current_screen( 'dashboard' );
 		reset_phpmailer_instance();
 	}
@@ -72,10 +75,10 @@ public function set_up() {
 	public function tear_down() {
 		reset_phpmailer_instance();
 
-		unset( $GLOBALS['locale'] );
-
 		restore_previous_locale();
 		parent::tear_down();
+
+		unset( $GLOBALS['locale'] );
 	}
 
 	/**