Added todo

Author: WalterWoshid

TODO.md

@@ -22,3 +22,6 @@ need optimization (e.g. Profilers or benchmarking suites).
 - Document how to use xdebug with php-unit tests that use the 
   `#[RunTestsInSeparateProcesses]` attribute (PhpStorm)
 - Create a flowchart
+
+# 7. Testing
+- Add tests for the `order` property of the `Transformer` class

tests/Functional/Workflow/B_CachedApplicationTest.php

@@ -12,6 +12,9 @@
 
 /**
  * This test has to be run after ApplicationTest.
+ *
+ * @todo For some reason, it takes a long time for me until this test is
+ *       executed. Maybe because of RunClassInSeparateProcess?
  */
 #[RunClassInSeparateProcess]
 class B_CachedApplicationTest extends TestCase