diff --git a/core/lib/Drupal/Core/Test/RunTests/TestFileParser.php b/core/lib/Drupal/Core/Test/RunTests/TestFileParser.php
index afd92df5e4..12aa757e57 100644
--- a/core/lib/Drupal/Core/Test/RunTests/TestFileParser.php
+++ b/core/lib/Drupal/Core/Test/RunTests/TestFileParser.php
@@ -2,7 +2,6 @@
 
 namespace Drupal\Core\Test\RunTests;
 
-use Drupal\simpletest\TestBase;
 use PHPUnit\Framework\TestCase;
 
 /**
@@ -24,7 +23,7 @@ class TestFileParser {
   public function getTestListFromFile($file) {
     $test_list = $this->parseContents(file_get_contents($file));
     return array_filter($test_list, function ($class) {
-      return (is_subclass_of($class, TestCase::class) || is_subclass_of($class, TestBase::class));
+      return is_subclass_of($class, TestCase::class);
     });
   }
 
diff --git a/core/lib/Drupal/Core/Test/TestDiscovery.php b/core/lib/Drupal/Core/Test/TestDiscovery.php
index 89287b5503..a0fa2ceaba 100644
--- a/core/lib/Drupal/Core/Test/TestDiscovery.php
+++ b/core/lib/Drupal/Core/Test/TestDiscovery.php
@@ -8,10 +8,11 @@
 use Drupal\Core\Extension\ExtensionDiscovery;
 use Drupal\Core\Test\Exception\MissingGroupException;
 use Drupal\TestTools\PhpUnitCompatibility\ClassWriter;
-use PHPUnit\Util\Test;
 
 /**
  * Discovers available tests.
+ *
+ * @internal
  */
 class TestDiscovery {
 
@@ -98,8 +99,6 @@ public function registerTestNamespaces() {
       if (!isset($existing["Drupal\\$name\\"])) {
         $this->classLoader->addPsr4("Drupal\\$name\\", "$base_path/src");
       }
-      // Add Simpletest test namespace.
-      $this->testNamespaces["Drupal\\$name\\Tests\\"][] = "$base_path/src/Tests";
 
       // Add PHPUnit test namespaces.
       $this->testNamespaces["Drupal\\Tests\\$name\\Unit\\"][] = "$base_path/tests/src/Unit";
@@ -182,20 +181,6 @@ public function getTestClasses($extension = NULL, array $types = []) {
         // abstract class, trait or test fixture.
         continue;
       }
-      // Skip this test class if it is a Simpletest-based test and requires
-      // unavailable modules. TestDiscovery should not filter out module
-      // requirements for PHPUnit-based test classes.
-      // @todo Move this behavior to \Drupal\simpletest\TestBase so tests can be
-      //   marked as skipped, instead.
-      // @see https://www.drupal.org/node/1273478
-      if ($info['type'] == 'Simpletest') {
-        if (!empty($info['requires']['module'])) {
-          if (array_diff($info['requires']['module'], $this->availableExtensions['module'])) {
-            continue;
-          }
-        }
-      }
-
       foreach ($info['groups'] as $group) {
         $list[$group][$classname] = $info;
       }
@@ -322,11 +307,8 @@ public static function scanDirectory($namespace_prefix, $path) {
    *   - group: The test's first @group (parsed from PHPDoc annotations).
    *   - groups: All of the test's @group annotations, as an array (parsed from
    *     PHPDoc annotations).
-   *   - requires: An associative array containing test requirements parsed from
-   *     PHPDoc annotations:
-   *     - module: List of Drupal module extension names the test depends on.
    *
-   * @throws \Drupal\simpletest\Exception\MissingGroupException
+   * @throws \Drupal\Core\Test\Exception\MissingGroupException
    *   If the class does not have a @group annotation.
    */
   public static function getTestInfo($classname, $doc_comment = NULL) {
@@ -363,14 +345,7 @@ public static function getTestInfo($classname, $doc_comment = NULL) {
     }
     $info['group'] = $annotations['group'];
     $info['groups'] = $annotations['groups'];
-
-    // Sort out PHPUnit-runnable tests by type.
-    if ($testsuite = static::getPhpunitTestSuite($classname)) {
-      $info['type'] = 'PHPUnit-' . $testsuite;
-    }
-    else {
-      $info['type'] = 'Simpletest';
-    }
+    $info['type'] = 'PHPUnit-' . static::getPhpunitTestSuite($classname);
 
     if (!empty($annotations['coversDefaultClass'])) {
       $info['description'] = 'Tests ' . $annotations['coversDefaultClass'] . '.';
@@ -378,9 +353,6 @@ public static function getTestInfo($classname, $doc_comment = NULL) {
     else {
       $info['description'] = static::parseTestClassSummary($doc_comment);
     }
-    if (isset($annotations['dependencies'])) {
-      $info['requires']['module'] = array_map('trim', explode(',', $annotations['dependencies']));
-    }
 
     return $info;
   }
@@ -414,42 +386,6 @@ public static function parseTestClassSummary($doc_comment) {
     return implode(' ', $summary);
   }
 
-  /**
-   * Parses annotations in the phpDoc of a test class.
-   *
-   * @param \ReflectionClass $class
-   *   The reflected test class.
-   *
-   * @return array
-   *   An associative array that contains all annotations on the test class;
-   *   typically including:
-   *   - group: A list of @group values.
-   *   - requires: An associative array of @requires values; e.g.:
-   *     - module: A list of Drupal module dependencies that are required to
-   *       exist.
-   *
-   * @see \PHPUnit\Util\Test::parseTestMethodAnnotations()
-   * @see http://phpunit.de/manual/current/en/incomplete-and-skipped-tests.html#incomplete-and-skipped-tests.skipping-tests-using-requires
-   */
-  public static function parseTestClassAnnotations(\ReflectionClass $class) {
-    $annotations = Test::parseTestMethodAnnotations($class->getName())['class'];
-
-    // @todo Enhance PHPUnit upstream to allow for custom @requires identifiers.
-    // @see \PHPUnit\Util\Test::getRequirements()
-    // @todo Add support for 'PHP', 'OS', 'function', 'extension'.
-    // @see https://www.drupal.org/node/1273478
-    if (isset($annotations['requires'])) {
-      foreach ($annotations['requires'] as $i => $value) {
-        [$type, $value] = explode(' ', $value, 2);
-        if ($type === 'module') {
-          $annotations['requires']['module'][$value] = $value;
-          unset($annotations['requires'][$i]);
-        }
-      }
-    }
-    return $annotations;
-  }
-
   /**
    * Determines the phpunit testsuite for a given classname, based on namespace.
    *
diff --git a/core/lib/Drupal/Core/Test/TestRunnerKernel.php b/core/lib/Drupal/Core/Test/TestRunnerKernel.php
index d5ec4573f1..c8736a303e 100644
--- a/core/lib/Drupal/Core/Test/TestRunnerKernel.php
+++ b/core/lib/Drupal/Core/Test/TestRunnerKernel.php
@@ -4,12 +4,13 @@
 
 use Drupal\Core\DrupalKernel;
 use Drupal\Core\Extension\Extension;
-use Drupal\Core\Extension\ExtensionDiscovery;
 use Drupal\Core\Site\Settings;
 use Symfony\Component\HttpFoundation\Request;
 
 /**
  * Kernel for run-tests.sh.
+ *
+ * @internal
  */
 class TestRunnerKernel extends DrupalKernel {
 
@@ -40,13 +41,6 @@ public function __construct($environment, $class_loader, $allow_dumping = FALSE,
     $this->moduleData = [
       'system' => new Extension($this->root, 'module', 'core/modules/system/system.info.yml', 'system.module'),
     ];
-    // In order to support Simpletest in Drupal 9 conditionally include the
-    // module.
-    $extensions = (new ExtensionDiscovery($this->root, FALSE, [], 'ignore_site_path_does_not_exist'))->scan('module', FALSE);
-    if (isset($extensions['simpletest'])) {
-      $this->moduleList['simpletest'] = 0;
-      $this->moduleData['simpletest'] = $extensions['simpletest'];
-    }
   }
 
   /**
diff --git a/core/lib/Drupal/Core/Test/TestSetupTrait.php b/core/lib/Drupal/Core/Test/TestSetupTrait.php
index 24795a466e..f7ba3e0279 100644
--- a/core/lib/Drupal/Core/Test/TestSetupTrait.php
+++ b/core/lib/Drupal/Core/Test/TestSetupTrait.php
@@ -42,7 +42,6 @@ trait TestSetupTrait {
   /**
    * The public file directory for the test environment.
    *
-   * @see \Drupal\simpletest\TestBase::prepareEnvironment()
    * @see \Drupal\Tests\BrowserTestBase::prepareEnvironment()
    *
    * @var string
@@ -59,7 +58,6 @@ trait TestSetupTrait {
   /**
    * The private file directory for the test environment.
    *
-   * @see \Drupal\simpletest\TestBase::prepareEnvironment()
    * @see \Drupal\Tests\BrowserTestBase::prepareEnvironment()
    *
    * @var string
@@ -88,7 +86,6 @@ trait TestSetupTrait {
    * This value has to match the temporary directory created in
    * install_base_system() for test installs.
    *
-   * @see \Drupal\simpletest\TestBase::prepareEnvironment()
    * @see \Drupal\Tests\BrowserTestBase::prepareEnvironment()
    * @see install_base_system()
    *
@@ -104,7 +101,7 @@ trait TestSetupTrait {
   protected $testId;
 
   /**
-   * Returns the database connection to the site running Simpletest.
+   * Returns the database connection to the site under test.
    *
    * @return \Drupal\Core\Database\Connection
    *   The database connection to use for inserting assertions.
diff --git a/core/scripts/run-tests.sh b/core/scripts/run-tests.sh
index cf7c75045a..2c9c51d4d3 100755
--- a/core/scripts/run-tests.sh
+++ b/core/scripts/run-tests.sh
@@ -11,7 +11,6 @@
 use Drupal\Component\Utility\Timer;
 use Drupal\Core\Composer\Composer;
 use Drupal\Core\Database\Database;
-use Drupal\Core\File\Exception\FileException;
 use Drupal\Core\Test\EnvironmentCleaner;
 use Drupal\Core\Test\PhpUnitTestRunner;
 use Drupal\Core\Test\RunTests\TestFileParser;
@@ -22,7 +21,6 @@
 use PHPUnit\Framework\TestCase;
 use PHPUnit\Runner\Version;
 use Symfony\Component\Console\Output\ConsoleOutput;
-use Symfony\Component\Filesystem\Filesystem as SymfonyFilesystem;
 use Symfony\Component\HttpFoundation\Request;
 
 // Define some colors for display.
@@ -242,7 +240,7 @@ function simpletest_script_help() {
 
   --sqlite    A pathname to use for the SQLite database of the test runner.
               Required unless this script is executed with a working Drupal
-              installation that has Simpletest module installed.
+              installation.
               A relative pathname is interpreted relative to the Drupal root
               directory.
               Note that ':memory:' cannot be used, because this script spawns
@@ -288,7 +286,7 @@ function simpletest_script_help() {
 
               Runs just tests from the specified test type, for example
               run-tests.sh
-              (i.e. --types "Simpletest,PHPUnit-Functional")
+              (i.e. --types "PHPUnit-Unit,PHPUnit-Kernel")
 
   --directory Run all tests found within the specified file directory.
 
@@ -345,9 +343,8 @@ function simpletest_script_help() {
 sudo -u [wwwrun|www-data|etc] php ./core/scripts/{$args['script']}
   --url http://example.com/ --class "Drupal\block\Tests\BlockTest"
 
-Without a preinstalled Drupal site and enabled Simpletest module, specify a
-SQLite database pathname to create and the default database connection info to
-use in tests:
+Without a preinstalled Drupal site, specify a SQLite database pathname to create
+and the default database connection info to use in tests:
 
 sudo -u [wwwrun|www-data|etc] php ./core/scripts/{$args['script']}
   --sqlite /tmpfs/drupal/test.sqlite
@@ -626,9 +623,8 @@ function simpletest_script_setup_database($new = FALSE) {
   }
   Database::addConnectionInfo('default', 'default', $databases['default']['default']);
 
-  // If no --sqlite parameter has been passed, then Simpletest module is assumed
-  // to be installed, so the test runner database connection is the default
-  // database connection.
+  // If no --sqlite parameter has been passed, then the test runner database
+  // connection is the default database connection.
   if (empty($args['sqlite'])) {
     $sqlite = FALSE;
     $databases['test-runner']['default'] = $databases['default']['default'];
@@ -684,10 +680,10 @@ function simpletest_script_setup_database($new = FALSE) {
       }
     }
   }
-  // Verify that the Simpletest database schema exists by checking one table.
+  // Verify that the test result database schema exists by checking one table.
   try {
     if (!$schema->tableExists('simpletest')) {
-      simpletest_script_print_error('Missing Simpletest database schema. Either install Simpletest module or use the --sqlite parameter.');
+      simpletest_script_print_error('Missing test result database schema. Use the --sqlite parameter.');
       exit(SIMPLETEST_SCRIPT_EXIT_FAILURE);
     }
   }
@@ -780,10 +776,6 @@ function simpletest_script_execute_batch($test_classes) {
             $args['repeat'] = -1;
           }
         }
-        // Free-up space by removing any potentially created resources.
-        if (!$args['keep-results']) {
-          simpletest_script_cleanup($child['test_id'], $child['class'], $status['exitcode']);
-        }
 
         // Remove this child.
         unset($children[$cid]);
@@ -820,47 +812,10 @@ function simpletest_script_run_one_test($test_id, $test_class) {
   global $args;
 
   try {
-    // Default to status = success. This could mean that we didn't discover any
-    // tests and that none ran.
-    $status = SIMPLETEST_SCRIPT_EXIT_SUCCESS;
-    if (strpos($test_class, '::') > 0) {
-      [$class_name, $method] = explode('::', $test_class, 2);
-      $methods = [$method];
-    }
-    else {
-      $class_name = $test_class;
-      // Use empty array to run all the test methods.
-      $methods = [];
-    }
-    $test = new $class_name($test_id);
     if ($args['suppress-deprecations']) {
       putenv('SYMFONY_DEPRECATIONS_HELPER=disabled');
     }
-    if (is_subclass_of($test_class, TestCase::class)) {
-      $status = simpletest_script_run_phpunit($test_id, $test_class);
-    }
-    // If we aren't running a PHPUnit-based test, then we might have a
-    // Simpletest-based one. Ensure that: 1) The simpletest framework exists,
-    // and 2) that our test belongs to that framework.
-    elseif (class_exists('Drupal\simpletest\TestBase') && is_subclass_of($test_class, 'Drupal\simpletest\TestBase')) {
-      $test->dieOnFail = (bool) $args['die-on-fail'];
-      $test->verbose = (bool) $args['verbose'];
-      $test->run($methods);
-      simpletest_script_reporter_display_summary($test_class, $test->results);
-
-      $status = SIMPLETEST_SCRIPT_EXIT_SUCCESS;
-      // Finished, kill this runner.
-      if ($test->results['#fail'] || $test->results['#exception']) {
-        $status = SIMPLETEST_SCRIPT_EXIT_FAILURE;
-      }
-    }
-    // If the test is not a PHPUnit test, and either we don't have the
-    // Simpletest module or the \Drupal\simpletest\TestBase class available.
-    else {
-      simpletest_script_print_error(sprintf('Can not run %s. If this is a WebTestBase test the simpletest module must be installed. See https://www.drupal.org/node/3030340', $test_class));
-      $status = SIMPLETEST_SCRIPT_EXIT_FAILURE;
-    }
-
+    $status = simpletest_script_run_phpunit($test_id, $test_class);
     exit($status);
   }
   // DrupalTestCase::run() catches exceptions already, so this is only reached
@@ -905,112 +860,6 @@ function simpletest_script_command($test_id, $test_class) {
   return $command;
 }
 
-/**
- * Removes all remnants of a test runner.
- *
- * In case a fatal error occurs after the test site has been fully setup and
- * the error happens in many tests, the environment that executes the tests can
- * easily run out of memory or disk space. This function ensures that all
- * created resources are properly cleaned up after every executed test.
- *
- * This clean-up only exists in this script, since SimpleTest module itself does
- * not use isolated sub-processes for each test being run, so a fatal error
- * halts not only the test, but also the test runner (i.e., the parent site).
- *
- * @param int $test_id
- *   The test ID of the test run.
- * @param string $test_class
- *   The class name of the test run.
- * @param int $exitcode
- *   The exit code of the test runner.
- *
- * @see simpletest_script_run_one_test()
- */
-function simpletest_script_cleanup($test_id, $test_class, $exitcode) {
-  if (is_subclass_of($test_class, TestCase::class)) {
-    // PHPUnit test, move on.
-    return;
-  }
-  // Retrieve the last database prefix used for testing.
-  try {
-    $last_test = TestDatabase::lastTestGet($test_id);
-    $db_prefix = $last_test['last_prefix'];
-  }
-  catch (Exception $e) {
-    echo (string) $e;
-    exit(SIMPLETEST_SCRIPT_EXIT_EXCEPTION);
-  }
-
-  // If no database prefix was found, then the test was not set up correctly.
-  if (empty($db_prefix)) {
-    echo "\nFATAL $test_class: Found no database prefix for test ID $test_id. (Check whether setUp() is invoked correctly.)";
-    return;
-  }
-
-  // Do not output verbose cleanup messages in case of a positive exitcode.
-  $output = !empty($exitcode);
-  $messages = [];
-
-  $messages[] = "- Found database prefix '$db_prefix' for test ID $test_id.";
-
-  // Read the log file in case any fatal errors caused the test to crash.
-  try {
-    (new TestDatabase($db_prefix))->logRead($test_id, $last_test['test_class']);
-  }
-  catch (Exception $e) {
-    echo (string) $e;
-    exit(SIMPLETEST_SCRIPT_EXIT_EXCEPTION);
-  }
-
-  // Check whether a test site directory was setup already.
-  // @see \Drupal\simpletest\TestBase::prepareEnvironment()
-  $test_db = new TestDatabase($db_prefix);
-  $test_directory = DRUPAL_ROOT . '/' . $test_db->getTestSitePath();
-  if (is_dir($test_directory)) {
-    // Output the error_log.
-    if (is_file($test_directory . '/error.log')) {
-      if ($errors = file_get_contents($test_directory . '/error.log')) {
-        $output = TRUE;
-        $messages[] = $errors;
-      }
-    }
-    // Delete the test site directory.
-    // simpletest_clean_temporary_directories() cannot be used here, since it
-    // would also delete file directories of other tests that are potentially
-    // running concurrently.
-    try {
-      \Drupal::service('file_system')->deleteRecursive($test_directory, ['\Drupal\Tests\BrowserTestBase', 'filePreDeleteCallback']);
-      $messages[] = "- Removed test site directory.";
-    }
-    catch (FileException $e) {
-      // Ignore failed deletes.
-    }
-  }
-
-  // Clear out all database tables from the test.
-  try {
-    $schema = Database::getConnection('default', 'default')->schema();
-    $count = 0;
-    foreach ($schema->findTables($db_prefix . '%') as $table) {
-      $schema->dropTable($table);
-      $count++;
-    }
-  }
-  catch (Exception $e) {
-    echo (string) $e;
-    exit(SIMPLETEST_SCRIPT_EXIT_EXCEPTION);
-  }
-
-  if ($count) {
-    $messages[] = "- Removed $count leftover tables.";
-  }
-
-  if ($output) {
-    echo implode("\n", $messages);
-    echo "\n";
-  }
-}
-
 /**
  * Get list of tests based on arguments.
  *
diff --git a/core/tests/Drupal/Tests/Core/Test/TestDiscoveryTest.php b/core/tests/Drupal/Tests/Core/Test/TestDiscoveryTest.php
index 51eb801daf..7a404091c9 100644
--- a/core/tests/Drupal/Tests/Core/Test/TestDiscoveryTest.php
+++ b/core/tests/Drupal/Tests/Core/Test/TestDiscoveryTest.php
@@ -84,46 +84,23 @@ public function infoParserProvider() {
       '\Drupal\Tests\file\Kernel\FileItemValidationTest',
     ];
 
-    // Simpletest classes can not be autoloaded in a PHPUnit test, therefore
-    // provide a docblock.
-    $tests[] = [
-      // Expected result.
-      [
-        'name' => 'Drupal\simpletest\Tests\ExampleSimpleTest',
-        'group' => 'simpletest',
-        'groups' => ['simpletest'],
-        'description' => 'Tests the Simpletest UI internal browser.',
-        'type' => 'Simpletest',
-      ],
-      // Classname.
-      'Drupal\simpletest\Tests\ExampleSimpleTest',
-      // Doc block.
-      "/**
- * Tests the Simpletest UI internal browser.
- *
- * @group simpletest
- */
- ",
-    ];
-
     // Test with a different amount of leading spaces.
     $tests[] = [
       // Expected result.
       [
-        'name' => 'Drupal\simpletest\Tests\ExampleSimpleTest',
-        'group' => 'simpletest',
-        'groups' => ['simpletest'],
-        'description' => 'Tests the Simpletest UI internal browser.',
-        'type' => 'Simpletest',
+        'name' => 'Drupal\Tests\ExampleSimpleTest',
+        'group' => 'test',
+        'groups' => ['test'],
+        'description' => 'Example test.',
+        'type' => 'PHPUnit-Unit',
       ],
       // Classname.
-      'Drupal\simpletest\Tests\ExampleSimpleTest',
+      'Drupal\Tests\ExampleSimpleTest',
       // Doc block.
       "/**
-   * Tests the Simpletest UI internal browser.
+   * Example test.
    *
-   * @group simpletest
-   */
+   * @group test
    */
  ",
     ];
@@ -133,19 +110,19 @@ public function infoParserProvider() {
     $tests[] = [
       // Expected result.
       [
-        'name' => 'Drupal\simpletest\Tests\ExampleSimpleTest',
-        'group' => 'simpletest',
-        'groups' => ['simpletest'],
-        'description' => 'Tests the Simpletest UI internal browser. * @',
-        'type' => 'Simpletest',
+        'name' => 'Drupal\Tests\ExampleSimpleTest',
+        'group' => 'test',
+        'groups' => ['test'],
+        'description' => 'Example test. * @',
+        'type' => 'PHPUnit-Unit',
       ],
       // Classname.
-      'Drupal\simpletest\Tests\ExampleSimpleTest',
+      'Drupal\Tests\ExampleSimpleTest',
       // Doc block.
       "/**
-   * Tests the Simpletest UI internal browser. * @
+   * Example test. * @
    *
-   * @group simpletest
+   * @group test
    */
  ",
     ];
@@ -154,20 +131,20 @@ public function infoParserProvider() {
     $tests[] = [
       // Expected result.
       [
-        'name' => 'Drupal\simpletest\Tests\ExampleSimpleTest',
-        'group' => 'Test',
-        'groups' => ['Test', 'simpletest'],
-        'description' => 'Tests the Simpletest UI internal browser.',
-        'type' => 'Simpletest',
+        'name' => 'Drupal\Tests\ExampleSimpleTest',
+        'group' => 'test1',
+        'groups' => ['test1', 'test2'],
+        'description' => 'Example test.',
+        'type' => 'PHPUnit-Unit',
       ],
       // Classname.
-      'Drupal\simpletest\Tests\ExampleSimpleTest',
+      'Drupal\Tests\ExampleSimpleTest',
       // Doc block.
       "/**
- * Tests the Simpletest UI internal browser.
+ * Example test.
  *
- * @group Test
- * @group simpletest
+ * @group test1
+ * @group test2
  */
  ",
     ];
@@ -176,20 +153,20 @@ public function infoParserProvider() {
     $tests['many-group-annotations'] = [
       // Expected result.
       [
-        'name' => 'Drupal\simpletest\Tests\ExampleSimpleTest',
-        'group' => 'Test',
-        'groups' => ['Test', 'simpletest', 'another', 'more', 'many', 'enough', 'whoa'],
-        'description' => 'Tests the Simpletest UI internal browser.',
-        'type' => 'Simpletest',
+        'name' => 'Drupal\Tests\ExampleSimpleTest',
+        'group' => 'test1',
+        'groups' => ['test1', 'test2', 'another', 'more', 'many', 'enough', 'whoa'],
+        'description' => 'Example test.',
+        'type' => 'PHPUnit-Unit',
       ],
       // Classname.
-      'Drupal\simpletest\Tests\ExampleSimpleTest',
+      'Drupal\Tests\ExampleSimpleTest',
       // Doc block.
       "/**
- * Tests the Simpletest UI internal browser.
+ * Example test.
  *
- * @group Test
- * @group simpletest
+ * @group test1
+ * @group test2
  * @group another
  * @group more
  * @group many
@@ -199,70 +176,24 @@ public function infoParserProvider() {
  ",
     ];
 
-    // @dependencies annotation.
-    $tests[] = [
-      // Expected result.
-      [
-        'name' => 'Drupal\simpletest\Tests\ExampleSimpleTest',
-        'description' => 'Tests the Simpletest UI internal browser.',
-        'type' => 'Simpletest',
-        'requires' => ['module' => ['test']],
-        'group' => 'simpletest',
-        'groups' => ['simpletest'],
-      ],
-      // Classname.
-      'Drupal\simpletest\Tests\ExampleSimpleTest',
-      // Doc block.
-      "/**
- * Tests the Simpletest UI internal browser.
- *
- * @dependencies test
- * @group simpletest
- */
- ",
-    ];
-
-    // Multiple @dependencies annotation.
-    $tests[] = [
-      // Expected result.
-      [
-        'name' => 'Drupal\simpletest\Tests\ExampleSimpleTest',
-        'description' => 'Tests the Simpletest UI internal browser.',
-        'type' => 'Simpletest',
-        'requires' => ['module' => ['test', 'test1', 'test2']],
-        'group' => 'simpletest',
-        'groups' => ['simpletest'],
-      ],
-      // Classname.
-      'Drupal\simpletest\Tests\ExampleSimpleTest',
-      // Doc block.
-      "/**
- * Tests the Simpletest UI internal browser.
- *
- * @dependencies test, test1, test2
- * @group simpletest
- */
- ",
-    ];
-
     // Multi-line summary line.
     $tests[] = [
       // Expected result.
       [
-        'name' => 'Drupal\simpletest\Tests\ExampleSimpleTest',
-        'description' => 'Tests the Simpletest UI internal browser. And the summary line continues an there is no gap to the annotation.',
-        'type' => 'Simpletest',
-        'group' => 'simpletest',
-        'groups' => ['simpletest'],
+        'name' => 'Drupal\Tests\ExampleSimpleTest',
+        'description' => 'Example test. And the summary line continues and there is no gap to the annotation.',
+        'type' => 'PHPUnit-Unit',
+        'group' => 'test',
+        'groups' => ['test'],
       ],
       // Classname.
-      'Drupal\simpletest\Tests\ExampleSimpleTest',
+      'Drupal\Tests\ExampleSimpleTest',
       // Doc block.
       "/**
- * Tests the Simpletest UI internal browser. And the summary line continues an
- * there is no gap to the annotation.
+ * Example test. And the summary line continues and there is no gap to the
+ * annotation.
  *
- * @group simpletest
+ * @group test
  */
  ",
     ];
diff --git a/core/tests/Drupal/Tests/Core/Test/TestRunnerKernelTest.php b/core/tests/Drupal/Tests/Core/Test/TestRunnerKernelTest.php
deleted file mode 100644
index 3fe432b186..0000000000
--- a/core/tests/Drupal/Tests/Core/Test/TestRunnerKernelTest.php
+++ /dev/null
@@ -1,104 +0,0 @@
-<?php
-
-namespace Drupal\Tests\Core\Test;
-
-use Composer\Autoload\ClassLoader;
-use Drupal\Core\Extension\Extension;
-use Drupal\Core\Test\TestRunnerKernel;
-use org\bovigo\vfs\vfsStream;
-use PHPUnit\Framework\TestCase;
-
-/**
- * @coversDefaultClass \Drupal\Core\Test\TestRunnerKernel
- * @runTestsInSeparateProcesses
- * @preserveGlobalState disabled
- * @group Test
- * @group simpletest
- */
-class TestRunnerKernelTest extends TestCase {
-
-  /**
-   * Data provider for self::testConstructor().
-   */
-  public function providerTestConstructor() {
-    $core = [
-      'core' => [
-        'modules' => [
-          'system' => [
-            'system.info.yml' => 'type: module',
-          ],
-        ],
-      ],
-    ];
-    $tests = [];
-    $tests['simpletest-in-contrib'] = [
-      $core + [
-        'modules' => [
-          'contrib' => [
-            'simpletest' => [
-              'simpletest.info.yml' => 'type: module',
-            ],
-          ],
-        ],
-      ],
-      'modules/contrib/simpletest',
-    ];
-
-    $tests['simpletest-simpletest-in-contrib'] = [
-      $core + [
-        'modules' => [
-          'contrib' => [
-            'simpletest-simpletest' => [
-              'simpletest.info.yml' => 'type: module',
-            ],
-          ],
-        ],
-      ],
-      'modules/contrib/simpletest-simpletest',
-    ];
-
-    $tests['simpletest-no-contrib'] = [
-      $core + [
-        'modules' => [
-          'simpletest' => [
-            'simpletest.info.yml' => 'type: module',
-          ],
-        ],
-      ],
-      'modules/simpletest',
-    ];
-
-    $tests['no-simpletest'] = [
-      $core,
-      FALSE,
-    ];
-
-    return $tests;
-  }
-
-  /**
-   * @covers ::__construct
-   * @dataProvider providerTestConstructor
-   */
-  public function testConstructor($file_system, $expected) {
-    // Set up the file system.
-    $vfs = vfsStream::setup('root');
-    vfsStream::create($file_system, $vfs);
-
-    $kernel = new TestRunnerKernel('prod', new ClassLoader(), FALSE, vfsStream::url('root'));
-    $class = new \ReflectionClass(TestRunnerKernel::class);
-    $instance_method = $class->getMethod('moduleData');
-    $instance_method->setAccessible(TRUE);
-    /** @var \Drupal\Core\Extension\Extension $extension */
-    $extension = $instance_method->invoke($kernel, 'simpletest');
-
-    if ($expected === FALSE) {
-      $this->assertFalse($extension);
-    }
-    else {
-      $this->assertInstanceOf(Extension::class, $extension);
-      $this->assertSame($expected, $extension->getPath());
-    }
-  }
-
-}