Testing - Put help methods in help classes (SAP#107)

* Testing - Put help methods in help classes

* Removed !

* Help class inheritance vs delegation

* Update CleanABAP.md

clean-abap/CleanABAP.md

@@ -204,6 +204,7 @@ The [Cheat Sheet](cheat-sheet/CheatSheet.md) is a print-optimized version.
   - [Test Classes](#test-classes)
     - [Call local test classes by their purpose](#call-local-test-classes-by-their-purpose)
     - [Put tests in local classes](#put-tests-in-local-classes)
+    - [Put help methods in help classes](#put-help-methods-in-help-classes)
     - [How to execute test classes](#how-to-execute-test-classes)
   - [Code Under Test](#code-under-test)
     - [Name the code under test meaningfully, or default to CUT](#name-the-code-under-test-meaningfully-or-default-to-cut)
@@ -4199,6 +4200,43 @@ class hiring_test defintion
 endclass.
 ```
 
+#### Put help methods in help classes
+
+> [Clean ABAP](#clean-abap) > [Content](#content) > [Testing](#testing) > [Test Classes](#test-classes) > [This section](#put-help-methods-in-help-classes)
+
+Put help methods used by several test classes in a help class. Make the help methods available through 
+inheritance (is-a relationship) or delegation (has-a relationship).
+
+```abap
+" inheritance example
+
+CLASS lth_unit_tests DEFINITION ABSTRACT FOR TESTING
+  DURATION SHORT
+  RISK LEVEL HARMLESS.
+
+  PROTECTED SECTION.
+    CLASS-METHODS assert_activity_entity
+      IMPORTING
+        actual_activity_entity TYPE REF TO zcl_activity_entity
+        expected_activity_entity TYPE REF TO zcl_activity_entity.
+    ...
+ENDCLASS.
+
+CLASS lth_unit_tests IMPLEMENTATION.
+
+  METHOD assert_activity_entity.
+    ...
+  ENDMETHOD.
+
+ENDCLASS.
+
+CLASS ltc_unit_tests DEFINITION INHERITING FROM lth_unit_tests FINAL FOR TESTING
+  DURATION SHORT
+  RISK LEVEL HARMLESS.
+  ...
+ENDCLASS.
+```
+
 #### How to execute test classes
 
 > [Clean ABAP](#clean-abap) > [Content](#content) > [Testing](#testing) > [Test Classes](#test-classes) > [This section](#how-to-execute-test-classes)