Issue #2244087 by cs_shadow, andrei.dincu, joachim: Add explanation comment in NodeCreationTestCase

modules/node/node.test

@@ -571,6 +571,8 @@ class NodeCreationTestCase extends DrupalWebTestCase {
     );
 
     try {
+      // An exception is generated by node_test_exception_node_insert() if the
+      // title is 'testing_transaction_exception'.
       node_save((object) $edit);
       $this->fail(t('Expected exception has not been thrown.'));
     }