diff --git a/core/modules/simpletest/tests/src/Unit/SimpletestPhpunitRunCommandTest.php b/core/modules/simpletest/tests/src/Unit/SimpletestPhpunitRunCommandTest.php
index 32aa058..10797a2 100644
--- a/core/modules/simpletest/tests/src/Unit/SimpletestPhpunitRunCommandTest.php
+++ b/core/modules/simpletest/tests/src/Unit/SimpletestPhpunitRunCommandTest.php
@@ -30,13 +30,14 @@ function testSimpletestPhpUnitRunCommand() {
     $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'));
+    $test_id = 77;
     foreach (['pass', 'fail'] as $status) {
       putenv('SimpletestPhpunitRunCommandTestWillDie=' . $status);
-      $ret = simpletest_run_phpunit_tests($test_id, ['Drupal\Tests\simpletest\Unit\SimpletestPhpunitRunCommandTestWillDie']);
+      $ret = simpletest_run_phpunit_tests($test_id++, ['Drupal\Tests\simpletest\Unit\SimpletestPhpunitRunCommandTestWillDie']);
       $this->assertSame($ret[0]['status'], $status);
     }
-    unlink(simpletest_phpunit_xml_filepath($test_id));
+    unlink(simpletest_phpunit_xml_filepath(--$test_id));
+    unlink(simpletest_phpunit_xml_filepath(--$test_id));
   }
 
 }