Issue #3298906 by andypost, alexpott: Fix \Drupal\Tests\Core\Test\TestSetupTraitTest::testChangeDatabasePrefix() on PHP 8.2

core/lib/Drupal/Core/Test/TestSetupTrait.php

@@ -80,6 +80,20 @@ trait TestSetupTrait {
    */
   protected $kernel;
 
+  /**
+   * The database prefix of this test run.
+   *
+   * @var string
+   */
+  protected $databasePrefix;
+
+  /**
+   * The app root.
+   *
+   * @var string
+   */
+  protected $root;
+
   /**
    * The temporary file directory for the test environment.
    *

core/tests/Drupal/TestSite/Commands/TestSiteInstallCommand.php

@@ -46,13 +46,6 @@ class TestSiteInstallCommand extends Command {
    */
   protected $timeLimit = 500;
 
-  /**
-   * The database prefix of this test run.
-   *
-   * @var string
-   */
-  protected $databasePrefix;
-
   /**
    * The language to install the site in.
    *

core/tests/Drupal/Tests/BrowserTestBase.php

@@ -73,13 +73,6 @@ abstract class BrowserTestBase extends TestCase {
   use ExpectDeprecationTrait;
   use ExtensionListTestTrait;
 
-  /**
-   * The database prefix of this test run.
-   *
-   * @var string
-   */
-  protected $databasePrefix;
-
   /**
    * Time limit in seconds for the test.
    *
@@ -201,13 +194,6 @@ abstract class BrowserTestBase extends TestCase {
    */
   protected $originalShutdownCallbacks = [];
 
-  /**
-   * The app root.
-   *
-   * @var string
-   */
-  protected $root;
-
   /**
    * The original container.
    *

core/tests/Drupal/Tests/Core/Test/TestSetupTraitTest.php

@@ -35,8 +35,10 @@ class TestSetupTraitTest extends UnitTestCase {
     // Create a mock for testing the trait and set a few properties that are
     // used to avoid unnecessary set up.
     $test_setup = $this->getMockForTrait(TestSetupTrait::class);
-    $test_setup->databasePrefix = 'testDbPrefix';
+
-    $test_setup->root = $root;
+    $reflection = new \ReflectionClass($test_setup);
+    $reflection->getProperty('databasePrefix')->setValue($test_setup, 'testDbPrefix');
+    $reflection->getProperty('root')->setValue($test_setup, $root);
 
     $method = new \ReflectionMethod(get_class($test_setup), 'changeDatabasePrefix');
     $method->setAccessible(TRUE);