This "app" exists to demonstrate unit testing using the Strobl Approach with mocks originated using the Mocker application. The app's functionality is trivial and uses code from FunWithParticleEmitters.
The app's view controller is provided by a VIPER module called "Main". VIPER was used here because it allows demonstrating unit testing of the presenter and the interactor.
A "Demonstration" facade is implemented. One of the methods in the facade is used in the application. The other two methods are invented to illustrate unit testing techniques.
Several protocols are defined so that Foundation classes can be dependency injected into objects for control during unit testing. In the project, the following protocols are created:
| Protocol | Related Foundation Class | Implementation |
|---|---|---|
DataRetreiving |
URLSession |
FoundationDataRetreiver |
FileManaging |
FileManager |
|
NotificationPosting |
NotificationCenter |
|
TimerFactory |
Timer |
FoundationTimerFactory |
Timing |
Timer |
Mocks for all of the protocols are included in the unit test code.
The interactor and presenter implementations are pretty bland for the Main module. However, 100% unit test code coverage is achieved on these objects providing a high level of confidence in the correctness of their implementations. Pay attention to the objects injected into the interactor and presenter.
The presenter is interesting because it uses a timer to determine when to tell the view to remove the particle emitter and show the "Tap Me" button again. The showConfetti() and showSnow() use three unit tests to cover all the code, including handling the timer firing.
| Tested Method | Test for nil View | Test to Create Timer but not fire | Test to Create and Fire Timer |
|---|---|---|---|
showConfetti() |
testShowConfetti_viewIsNil |
testShowConfetti_timerCreatedButNotFired |
testShowConfetti_timerCreatedAndFired |
showSnow() |
testShowSnow_viewIsNil |
testShowSnow_timerCreatedButNotFired |
testShowSnow_timerCreatedAndFired |
100% code coverage is also achieved on the DemonstrationFacade.
The tests for retrieveSomeData(from url: URL) demonstrate testing a network call. They execute both a failed attempt (where an error is thrown) and a successful attempt. In an actual implementation, where there may be an inspection of the response and conversion of the response data into data transfer objects (DTO), the logic for all the processing steps can be tested because of the ability to control the response and the injected components completely.
Likewise, the tests for pretendToCheckForFile(at url: URL) can also be perfectly controlled. When you have to do file operations, executing the error paths can be extremely difficult. The Strobl Approach makes constructing tests that perform all paths within a method possible.