diff --git a/core/modules/simpletest/tests/fixtures/simpletest_phpunit_run_command_test.php b/core/modules/simpletest/tests/fixtures/simpletest_phpunit_run_command_test.php
index 3b6984e..80d1679 100644
--- a/core/modules/simpletest/tests/fixtures/simpletest_phpunit_run_command_test.php
+++ b/core/modules/simpletest/tests/fixtures/simpletest_phpunit_run_command_test.php
@@ -2,9 +2,6 @@
 
 namespace Drupal\Tests\simpletest\Unit;
 
-use Drupal\Core\Test\TestStatus;
-use Drupal\Tests\UnitTestCase;
-
 /**
  * This test crashes PHP.
  *
@@ -12,21 +9,19 @@
  * file name does not adhere to PSR-4 and an environment variable also needs to
  * be set for the crash to happen.
  *
- * @see \Drupal\Tests\simpletest\Unit::testSimpletestPhpUnitRunCommand()
+ * @see \Drupal\Tests\simpletest\Unit\SimpletestPhpunitRunCommandTest::testSimpletestPhpUnitRunCommand()
  */
-class SimpletestPhpunitRunCommandTestWillDie extends UnitTestCase {
+class SimpletestPhpunitRunCommandTestWillDie extends \PHPUnit_Framework_TestCase {
 
+  /**
+   * Performs the status specified by SimpletestPhpunitRunCommandTestWillDie.
+   */
   public function testWillDie() {
-    if (getenv('SimpletestPhpunitRunCommandTestWillDie') === 'fail') {
-      exit(TestStatus::FAIL);
-    }
-    if (getenv('SimpletestPhpunitRunCommandTestWillDie') === 'exception') {
-      exit(TestStatus::EXCEPTION);
-    }
-    if (getenv('SimpletestPhpunitRunCommandTestWillDie') === 'error') {
-      exit(TestStatus::SYSTEM);
+    $status = (int)getenv('SimpletestPhpunitRunCommandTestWillDie');
+    if ($status == 0) {
+      $this->assertTrue(TRUE, 'Assertion to ensure test pass');
     }
-    $this->assertTrue(TRUE, 'Assertion to ensure test pass');
+    else exit($status);
   }
 
 }
diff --git a/core/modules/simpletest/tests/src/Unit/SimpletestPhpunitRunCommandTest.php b/core/modules/simpletest/tests/src/Unit/SimpletestPhpunitRunCommandTest.php
index 688e38c..c6e8ec8 100644
--- a/core/modules/simpletest/tests/src/Unit/SimpletestPhpunitRunCommandTest.php
+++ b/core/modules/simpletest/tests/src/Unit/SimpletestPhpunitRunCommandTest.php
@@ -3,35 +3,99 @@
 namespace Drupal\Tests\simpletest\Unit;
 
 use Drupal\Core\DependencyInjection\ContainerBuilder;
-use Drupal\Tests\UnitTestCase;
+use Drupal\Core\File\FileSystemInterface;
+use Drupal\Tests\simpletest\Unit\SimpletestPhpunitRunCommandTestWillDie;
 
 /**
  * Tests simpletest_run_phpunit_tests() handles PHPunit fatals correctly.
  *
  * @group simpletest
- *
- * @runTestsInSeparateProcesses
- * @preserveGlobalState disabled
  */
-class SimpletestPhpunitRunCommandTest extends UnitTestCase {
+class SimpletestPhpunitRunCommandTest extends \PHPUnit_Framework_TestCase {
+
+  /**
+   * Path to the app root.
+   *
+   * @var string
+   */
+  protected static $root;
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function setUpBeforeClass() {
+    parent::setUpBeforeClass();
+    // Figure out our app root.
+    self::$root = dirname(dirname(dirname(dirname(dirname(dirname(__DIR__))))));
+    // Include the files we need for tests. The stub test we will run is
+    // SimpletestPhpunitRunCommandTestWillDie which is located in
+    // simpletest_phpunit_run_command_test.php.
+    include_once self::$root . '/core/modules/simpletest/tests/fixtures/simpletest_phpunit_run_command_test.php';
+    // Since we're testing simpletest_run_phpunit_tests(), we need to include
+    // simpletest.module.
+    include_once self::$root . '/core/modules/simpletest/simpletest.module';
+  }
 
-  function testSimpletestPhpUnitRunCommand() {
-    include_once __DIR__ . '/../../fixtures/simpletest_phpunit_run_command_test.php';
-    $app_root = __DIR__ . '/../../../../../..';
-    include_once "$app_root/core/modules/simpletest/simpletest.module";
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp() {
+    parent::setUp();
+    // Organize our mock container.
     $container = new ContainerBuilder();
-    $container->set('app.root', $app_root);
-    $file_system = $this->prophesize('Drupal\Core\File\FileSystemInterface');
+    $container->set('app.root', self::$root);
+    $file_system = $this->prophesize(FileSystemInterface::class);
+    // The simpletest directory wrapper will always point to /tmp.
     $file_system->realpath('public://simpletest')->willReturn(sys_get_temp_dir());
     $container->set('file_system', $file_system->reveal());
     \Drupal::setContainer($container);
-    $test_id = basename(tempnam(sys_get_temp_dir(), 'xxx'));
-    foreach (['pass', 'fail', 'exception', 'error'] as $status) {
-      putenv('SimpletestPhpunitRunCommandTestWillDie=' . $status);
-      $ret = simpletest_run_phpunit_tests($test_id, ['Drupal\Tests\simpletest\Unit\SimpletestPhpunitRunCommandTestWillDie']);
-      $this->assertSame($ret[0]['status'], $status);
+  }
+
+  /**
+   * Data provider for testSimpletestPhpUnitRunCommand().
+   *
+   * @return array
+   *   Arrays of status codes and the label they're expected to have.
+   */
+  public function provideStatusCodes() {
+    $data = [
+      [0, 'pass'],
+      [1, 'fail'],
+      [2, 'exception'],
+    ];
+    // All status codes 3 and above should be labeled 'error'.
+    // @todo: The valid values here would be 3 to 127. But since the test
+    // touches the file system a lot, we only have 3, 4, and 127 for speed.
+    foreach ([3, 4, 127] as $status) {
+      $data[] = [$status, 'error'];
     }
+    return $data;
+  }
+
+  /**
+   * Test the round trip for PHPUnit execution status codes.
+   *
+   * @covers ::simpletest_run_phpunit_tests
+   *
+   * @dataProvider provideStatusCodes
+   */
+  public function testSimpletestPhpUnitRunCommand($status, $label) {
+    $test_id = basename(tempnam(sys_get_temp_dir(), 'xxx'));
+    putenv('SimpletestPhpunitRunCommandTestWillDie=' . $status);
+    $ret = simpletest_run_phpunit_tests($test_id, [SimpletestPhpunitRunCommandTestWillDie::class]);
+    $this->assertSame($ret[0]['status'], $label);
+    putenv('SimpletestPhpunitRunCommandTestWillDie');
     unlink(simpletest_phpunit_xml_filepath($test_id));
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  protected function tearDown() {
+    // We unset the $base_url global, since the test code sets it as a
+    // side-effect.
+    unset($GLOBALS['base_url']);
+    parent::tearDown();
+  }
+
 }