diff --git a/core/lib/Drupal/Core/Test/TestDiscovery.php b/core/lib/Drupal/Core/Test/TestDiscovery.php
index d87844772a..e1510688d0 100644
--- a/core/lib/Drupal/Core/Test/TestDiscovery.php
+++ b/core/lib/Drupal/Core/Test/TestDiscovery.php
@@ -221,10 +221,13 @@ public function getTestClasses($extension = NULL, array $types = []) {
    * @param array $test_list
    *   An array of tests keyed by the the group name.
    *
-   * @todo Remove this when we deprecate simpletest module.
+   * @todo Remove this when the simpletest module no longer needs to fire its
+   *   hook.
    *
    * @see hook_simpletest_alter()
    * @see https://www.drupal.org/project/drupal/issues/2866082
+   * @see https://www.drupal.org/node/2939892
+   * @see https://www.drupal.org/node/2949692
    */
   protected function alterHook(&$test_list) {
     return;
diff --git a/core/modules/simpletest/src/Exception/MissingGroupException.php b/core/modules/simpletest/src/Exception/MissingGroupException.php
index 0a2ba6cd14..613d585ddb 100644
--- a/core/modules/simpletest/src/Exception/MissingGroupException.php
+++ b/core/modules/simpletest/src/Exception/MissingGroupException.php
@@ -2,14 +2,14 @@
 
 namespace Drupal\simpletest\Exception;
 
-@trigger_error('Deprecated in Drupal 8.6.x for removal before Drupal 9.0.0 release. Use \Drupal\Core\Test\Exception\MissingGroupException instead. https://www.drupal.org/node/2949692', E_USER_DEPRECATED);
+@trigger_error('Deprecated in Drupal 8.7.x for removal before Drupal 9.0.0 release. Use \Drupal\Core\Test\Exception\MissingGroupException instead. https://www.drupal.org/node/2949692', E_USER_DEPRECATED);
 
 use Drupal\Core\Test\Exception\MissingGroupException as CoreMissingGroupException;
 
 /**
  * Exception thrown when a simpletest class is missing an @group annotation.
  *
- * @deprecated in Drupal 8.4.x for removal before Drupal 9.0.0 release. Use
+ * @deprecated in Drupal 8.7.x for removal before Drupal 9.0.0 release. Use
  *   \Drupal\Core\Test\Exception\MissingGroupException instead.
  *
  * @see \Drupal\Core\Test\Exception\MissingGroupException
diff --git a/core/tests/Drupal/Tests/Core/Test/TestDiscoveryTest.php b/core/tests/Drupal/Tests/Core/Test/TestDiscoveryTest.php
index b076debaf4..9d7c10cc62 100644
--- a/core/tests/Drupal/Tests/Core/Test/TestDiscoveryTest.php
+++ b/core/tests/Drupal/Tests/Core/Test/TestDiscoveryTest.php
@@ -436,8 +436,7 @@ public function testGetTestClassesWithSelectedTypes() {
     $result = $test_discovery->getTestClasses(NULL, ['PHPUnit-Kernel']);
     $this->assertCount(4, $result);
     $this->assertEquals([
-      'example' => [
-      ],
+      'example' => [],
       'example2' => [
         'Drupal\Tests\test_module\Kernel\KernelExampleTest3' => [
           'name' => 'Drupal\Tests\test_module\Kernel\KernelExampleTest3',