ABAP_to_the_Future

3
ABAP Unit and Test-Driven Development
Mock Objects vs. Stub Objects
When talking about mock objects, the terms stub and mock are often used interchangeably;
technically, though, there is a differen ce. If you are testing how your class affects
an external system, then the fake external system is a mock, and if you are testing how
the fake external system affects your class, then the fake external system is a stub.
(Either way, the point is that you use a fake external system for testing.)
3.2.1 Creating Mock Objects
For testing purposes, you want to define mock classes and mock objects. Mock
classes are classes that run in the development environment. They don’t really try
to read and write to the database, send emails, fire nuclear missiles, and so on, but
they test the business logic nonetheless. Mock objects follow the same principles
as regular objects; i.e., in the same way that a monster object is an instance of the
real monster class, a mock monster object is an instance of a mock monster class.
This is where the basic features of object-oriented programming come into play:
subclasses and interfaces. To continue the previous example, you’ll next create a
subclass of the database access class that doesn’t actually read the database but
instead redefines the database access methods to return hard-coded values based
upon the values passed in. In Listing 3. 3, you’ll see some possible redefined
implementations of methods in mock subclasses that could replace the real classes
in the example.
METHOD read_customising. "mock database implementation
*--------------------------------------------------------------*
* IMPORTING input_value
* EXPORTING export_vlaue
*--------------------------------------------------------------*
CASE input_value.
WHEN one_value.
export_value = something.
WHEN another_value.
export_value = something_else.
WHEN OTHERS.
export_value = something_else_again.
ENDCASE.
ENDMETHOD. "read customising mock database implementation
METHOD popup_to_confirm. "mock user interface implementation
*--------------------------------------------------------------*
* RETURNING rd_answer TYPE char01
*--------------------------------------------------------------*
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