Issue #2949363 by vaplas, Mile23, timmillwood, alexpott, Lendude: Impossible to make trigger_error in some files without test fails

core/modules/simpletest/src/TestDiscovery.php

@@ -325,7 +325,7 @@ class TestDiscovery {
    *   If the class does not have a @group annotation.
    */
   public static function getTestInfo($classname, $doc_comment = NULL) {
-    if (!$doc_comment) {
+    if ($doc_comment === NULL) {
       $reflection = new \ReflectionClass($classname);
       $doc_comment = $reflection->getDocComment();
     }

core/modules/simpletest/tests/src/Unit/TestDiscoveryTest.php

@@ -385,6 +385,21 @@ EOF;
     return $data;
   }
 
+  /**
+   * Ensure that classes are not reflected when the docblock is empty.
+   *
+   * @covers ::getTestInfo
+   */
+  public function testGetTestInfoEmptyDocblock() {
+    // If getTestInfo() performed reflection, it won't be able to find the
+    // class we asked it to analyze, so it will throw a ReflectionException.
+    // We want to make sure it didn't do that, because we already did some
+    // analysis and already have an empty docblock. getTestInfo() will throw
+    // MissingGroupException because the annotation is empty.
+    $this->setExpectedException(MissingGroupException::class);
+    TestDiscovery::getTestInfo('Drupal\Tests\simpletest\ThisTestDoesNotExistTest', '');
+  }
+
 }
 
 class TestTestDiscovery extends TestDiscovery {