diff --git a/docker-compose.yml b/docker-compose.yml
index 7fe9b524c7..060fd130e9 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -41,6 +41,8 @@ services:
       - LOCAL_PHP_MEMCACHED=${LOCAL_PHP_MEMCACHED-false}
       - PHP_FPM_UID=${PHP_FPM_UID-1000}
       - PHP_FPM_GID=${PHP_FPM_GID-1000}
+      - GITHUB_REF=${GITHUB_REF-false}
+      - GITHUB_EVENT_NAME=${GITHUB_EVENT_NAME-false}
 
     volumes:
       - ./tools/local-env/php-config.ini:/usr/local/etc/php/conf.d/php-config.ini
diff --git a/tests/phpunit/includes/abstract-testcase.php b/tests/phpunit/includes/abstract-testcase.php
index 765b514aa9..c0dc30b189 100644
--- a/tests/phpunit/includes/abstract-testcase.php
+++ b/tests/phpunit/includes/abstract-testcase.php
@@ -202,20 +202,20 @@ abstract class WP_UnitTestCase_Base extends PHPUnit_Adapter_TestCase {
 	/**
 	 * Allows tests to be skipped on some automated runs.
 	 *
-	 * For test runs on GitHub Actions for something other than trunk/master,
-	 * we want to skip tests that only need to run for master.
+	 * For test runs on GitHub Actions for something other than trunk,
+	 * we want to skip tests that only need to run for trunk.
 	 */
 	public function skipOnAutomatedBranches() {
 		// https://docs.github.com/en/free-pro-team@latest/actions/reference/environment-variables#default-environment-variables
 		$github_event_name = getenv( 'GITHUB_EVENT_NAME' );
 		$github_ref        = getenv( 'GITHUB_REF' );
 
-		if ( $github_event_name && 'false' !== $github_event_name ) {
+		if ( $github_event_name ) {
 			// We're on GitHub Actions.
 			$skipped = array( 'pull_request', 'pull_request_target' );
 
-			if ( in_array( $github_event_name, $skipped, true ) || 'refs/heads/master' !== $github_ref ) {
-				$this->markTestSkipped( 'For automated test runs, this test is only run on trunk/master' );
+			if ( in_array( $github_event_name, $skipped, true ) || 'refs/heads/trunk' !== $github_ref ) {
+				$this->markTestSkipped( 'For automated test runs, this test is only run on trunk' );
 			}
 		}
 	}
diff --git a/tests/phpunit/tests/basic.php b/tests/phpunit/tests/basic.php
index 05fdbeaf29..1a9e189ca3 100644
--- a/tests/phpunit/tests/basic.php
+++ b/tests/phpunit/tests/basic.php
@@ -8,7 +8,7 @@
 class Tests_Basic extends WP_UnitTestCase {
 
 	public function test_license() {
-		// This test is designed to only run on trunk/master.
+		// This test is designed to only run on trunk.
 		$this->skipOnAutomatedBranches();
 
 		$license = file_get_contents( ABSPATH . 'license.txt' );
@@ -18,7 +18,7 @@ class Tests_Basic extends WP_UnitTestCase {
 	}
 
 	public function test_security_md() {
-		// This test is designed to only run on trunk/master.
+		// This test is designed to only run on trunk.
 		$this->skipOnAutomatedBranches();
 
 		$security = file_get_contents( dirname( ABSPATH ) . '/SECURITY.md' );
diff --git a/tests/phpunit/tests/external-http/basic.php b/tests/phpunit/tests/external-http/basic.php
index b160e2b56f..16bef21847 100644
--- a/tests/phpunit/tests/external-http/basic.php
+++ b/tests/phpunit/tests/external-http/basic.php
@@ -10,7 +10,7 @@ class Tests_External_HTTP_Basic extends WP_UnitTestCase {
 	 * @covers ::wp_remote_retrieve_body
 	 */
 	public function test_readme_php_version() {
-		// This test is designed to only run on trunk/master.
+		// This test is designed to only run on trunk.
 		$this->skipOnAutomatedBranches();
 
 		$readme = file_get_contents( ABSPATH . 'readme.html' );
@@ -31,7 +31,7 @@ class Tests_External_HTTP_Basic extends WP_UnitTestCase {
 	 * @covers ::wp_remote_retrieve_body
 	 */
 	public function test_readme_mysql_version() {
-		// This test is designed to only run on trunk/master.
+		// This test is designed to only run on trunk.
 		$this->skipOnAutomatedBranches();
 
 		$readme = file_get_contents( ABSPATH . 'readme.html' );
@@ -63,7 +63,7 @@ class Tests_External_HTTP_Basic extends WP_UnitTestCase {
 	 * @covers ::wp_remote_retrieve_body
 	 */
 	public function test_readme_mariadb_version() {
-		// This test is designed to only run on trunk/master.
+		// This test is designed to only run on trunk.
 		$this->skipOnAutomatedBranches();
 
 		$readme = file_get_contents( ABSPATH . 'readme.html' );
diff --git a/tests/phpunit/tests/theme.php b/tests/phpunit/tests/theme.php
index e16dd4c900..14eccdf6da 100644
--- a/tests/phpunit/tests/theme.php
+++ b/tests/phpunit/tests/theme.php
@@ -213,7 +213,7 @@ class Tests_Theme extends WP_UnitTestCase {
 	 * @ticket 48566
 	 */
 	public function test_year_in_readme() {
-		// This test is designed to only run on trunk/master.
+		// This test is designed to only run on trunk.
 		$this->skipOnAutomatedBranches();
 
 		foreach ( $this->default_themes as $theme ) {