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Author's profile photo Uwe Kunath

mockA tutorial – How to create mocks

The previous blog post dealt with the question how fakes can be created using the new open source mocking framework mockA.

Fakes are mocked instances that return specific values when certain methods are called. In comparison to mocks, they do not validate if certain methods have been called or not.

The creation of fakes does not differ from the creation of mocks when you use mockA. Take a look at the setup routine of the unit test report ZTEST_CL_MOCKA_FLIGHT_OBSERVER that is ships with the framework.

In this unit test, a sample flight observer is to be tested. The flight observer depends on two other components, which are an object that provides some flight information as well as an object that processes alerts on specific late flights. The flight observer is determined to get the delay status of some sample flight data and delegate the creation of some alerts to the alert processor conditionally. While the flight information object serves as fake only, as it returns only sample data for specific flights (that is, method inputs), the alert processor serves as mock object that is subject to unit test assertions.

  Please note, that MO_ALERT_PROCESSOR_MOCKER is a member attribute which can be used for later use. The created mock object does not need to return any values. This means, the object is only created but no method output is specified.

**   Member attributes
 *    DATA mo_alert_processor_mocker TYPE REF TO ZIF_MOCKA_MOCKER.

 *   create an empty alert backend (we just need to track the number of method calls)
 mo_alert_processor_mocker = ZCL_MOCKA_MOCKER=>ZIF_MOCKA_MOCKER~mock(
     iv_interface = 'ZIF_MOCKA_FLIGHT_ALERT_PROCESS' ).
 *   this call creates the alert processor mockup
 mo_alert_processor ?= mo_alert_processor_mocker->generate_mockup( ).

If a certain method has been invoked on the mock object MO_ALERT_PROCESSOR can be checked later by the following call on its creator.

DATA lv_has_been_called TYPE apa_bool.
  lv_has_been_called =
 mo_alert_processor_mocker->has_method_been_called( 'ALERT_DELAY' ).

This kind of verification is usually needed in the assert-section of the unit test. Alternatively, you can access the exact method call count by calling this method:

DATA lv_method_call_count TYPE i.
  lv_method_call_count  =
 mo_alert_processor_mocker->method_call_count( 'ALERT_DELAY' ).

And that’s it. Besides the verification of a method call count, no other validation can be carried out against mock objects yet. In future releases, the verification if a specific method has been called with specific values could be implemented. This is one of the top priority functional gaps which exist for the framework right now.

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