Fake site should always be used for functional tests

Closes #3394705

tests/src/Functional/AutomaticUpdatesFunctionalTestBase.php

@@ -41,7 +41,6 @@ abstract class AutomaticUpdatesFunctionalTestBase extends BrowserTestBase {
    */
   protected function setUp(): void {
     parent::setUp();
-    $this->useFixtureDirectoryAsActive(__DIR__ . '/../../../package_manager/tests/fixtures/fake_site');
     // @todo Remove in https://www.drupal.org/project/automatic_updates/issues/3284443
     $this->config('automatic_updates.settings')
       ->set('unattended.level', CronUpdateRunner::SECURITY)
@@ -55,9 +54,16 @@ abstract class AutomaticUpdatesFunctionalTestBase extends BrowserTestBase {
   protected function installModulesFromClassProperty(ContainerInterface $container): void {
     $container->get('module_installer')->install([
       'package_manager_test_release_history',
+      'package_manager_bypass',
     ]);
     $this->container = $container->get('kernel')->getContainer();
 
+    // To prevent tests from using the real codebase for Composer we must set
+    // the fixture path as early as possible. Automatic Updates will run
+    // readiness checks when the module is installed so this must be done before
+    // the parent class installs the modules needed for the test.
+    $this->useFixtureDirectoryAsActive(__DIR__ . '/../../../package_manager/tests/fixtures/fake_site');
+
     // To prevent tests from making real requests to the Internet, use fake
     // release metadata that exposes a pretend Drupal 9.8.2 release.
     $this->setReleaseMetadata(__DIR__ . '/../../../package_manager/tests/fixtures/release-history/drupal.9.8.2.xml');