How to/Should I unit test EventBus events with Mockito?

问题:

I use Otto's EventBus in my Android app.

In my LoginNetworkOperation class, I catch different kinds of network connection errors and I post different bus events for each one, and my LoginPresenter class is registered as a listener and certain methods are invoked, when these events are fired.

My question is how (and should I) do I unit test whether the LoginNetworkOperation throws this event and LoginPresenter handles it with Mockito?

I looked at this question: Guava EventBus unit tests but it doesn't provide enough information, especially on the implementation part.

public class LoginNetworkOperation {      public void execute(String username, String password) {         try {             // retrofit attempt         } catch (Exception e) {             bus.post(new ExceptionEvent(e));         }     } }  public class LoginPresenter {      void onExceptionEvent(ExceptionEvent exceptionEvent) {         // Do Something with the exception event     } } 

Also, which should be the Subject Under Test here and which should be the mocked object?

I am using JUnit + Mockito + Robolectric in Android Studio and my test artifact is Unit Tests

回答1:

My question is how (and should I) do I unit test whether the LoginNetworkOperation throws this event and LoginPresenter handles it with Mockito?

That's already an integration test: you're combining individual software modules and verifying their behaviour as a group.

In that case the "subject under test" is the combination of LoginNetworkOperation, EventBus and LoginPresenter and the mocked objects are the inputs to LoginNetworkOperation and whatever handles the output of LoginPresenter.

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Those three software modules can also be unit tested:

• LoginNetworkOperation.execute: mock the EventBus and verify that it's called with the correct ExceptionEvent for different inputs.
• LoginPresenter.onExceptionEvent: verify correct behaviour for different ExceptionEvents.
• EventBus.post: register a mocked ExceptionEvent-Handler, post an ExceptionEvent and check that the Handler is called.

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