SAP ABAP Unit test for Static dependency method with a “hack”

What?

ABAP Unit tests using OO Test Double Framework is a great tool for writing tests. However it has many limitations. One such is, it does not support static methods. classes which are marked STATIC (as mentioned in here ).

Why?

While I was writing test cases I came across this scenario. And after some research I did not find a clear answer, which motivated me to write this blog post.

Although it is not possible to create a double for a class method which is static, out of the box. We can still simulate this using a “hack” (p.s. I love hacks! 😎 ).

In this blog post I will cover an approach using which we can write tests for dependency static class method.

How?

Using Dynamic Method Call

Procedure Steps :

• Replace original method call to dynamic call

METHOD cut_method.
    ...
    " Original Call
    cl_static_class_name=>method_name
    ...
ENDMETHOD.


METHOD cut_method.
    ...
    " Replace with
    (vairable_name)=>method_name
    ...
ENDMETHOD.

• Set Class name

This can be done using one of the two possible approaches. 

• • Create Class attribute – Assign Initial value. Can be done in constructor.

METHOD constructor.
    ...
    gv_class_attribue = 'CL_STATIC_CLASS_NAME'.
    ...
ENDMETHOD.

• • Create Method variable – Assign value before call

METHOD cut_method.
    ...
    lv_class_name_variable = 'CL_STATIC_CLASS_NAME'.
    ...
ENDMETHOD.

• Define and Implement local class with similar signature as dependency class

CLASS lcl_cut DEFINITION.
   PUBLIC SECTION.
     ...
     METHODS : cut_method ...
ENDCLASS.

CLASS lcl_cut IMPLEMENTATION.
   METHOD cut_method.
       ...
   ENDMETHOD.
ENDCLASS.

Note :

1. Method name must be same as in dependency class with all the IMPORT, EXPORT and CHANGING variables.
2. In the cut_method of newly created local class; based on some fixed values passed to it, both success and failure scenarios can be simulated.

• Modify Class name in Test Environment

Based on the approach used to Set Class name, Modify the Class name in Test Environment as shown below.

• • For Class attribute

METHOD utm.
    ...
    mo_cut->gv_static_class = 'lcl_cut'.
    ...
ENDMETHOD.

Note : Either the class attribute should be made public or local class should be made friends with CUT class.

• • For Method variable

METHOD cut_method.
    ...
    " Add test seam around variable assignment
    TEST-SEAM set_static_class_name.
        lv_class_name_variable = 'CL_STATIC_CLASS_NAME'.
    END-TEST-SEAM.
    ...
ENDMETHOD.

--------------------------------------------------------------------------
METHOD utm.
    ...
    TEST-INJECTION set_static_class_name.
      lv_class_name_variable = 'LCL_CUT'.
    END-TEST-INJECTION.
    ...
ENDMETHOD.

• Call CUT method

METHOD utm.
    ...
    mo->cut_method ...
    ...
ENDMETHOD.

Conclusion

We learnt how to simulate double for a Static class method with a hack. I hope this would be helpful to many of those who are working on implementing ABAP Unit tests for existing written code or following TDD (Test Driven Development) for new code.

I am planning to create such short blog posts around ABAP Unit tests. Please do let me know your thoughts on this post, any suggestions/ feedback you have or any further questions on the post.

One better approach is from Matthew Billingham, which does not use Dynamic Method call.