Reusing mock behavior / best practice in Mockito?

Question

I'll preface this with the background that I am very green and don't have much experience with testing in general, and have never used a mocking framework before.

I am writing unit tests for code that hits a lot of different web services, which I have mocked. Many of my tests verify the result of a call where all of my service calls are successful except a call to ServiceX. My first instinct was to set up happy-path behavior for all mocks in a @Before block and then modify the mock behavior for each test.

@Before
public void init(){
    when(serviceA.doSomething()).thenReturn(true);
    when(serviceB.doSomething()).thenReturn(true);
    when(serviceC.doSomething()).thenReturn(true);
    when(serviceD.doSomething()).thenReturn(true);
    when(serviceE.doSomething()).thenReturn(true);
}

@Test
public void testDoBusinessSuccess(){
    String result = businessLogic.doBusiness();
    assertThat(result, is("success"));
}

@Test
public void testDoBusinessFailureWhenServiceAFails(){
    when(serviceA.doSomething()).thenReturn(false);

    String result = businessLogic.doBusiness();
    assertThat(result, is("service A is down!"));
}

@Test
public void testDoBusinessFailureWhenServiceBFails(){
    when(serviceB.doSomething()).thenReturn(false);

...

which makes each test case succinct, and it is easy to see what is being tested, since I only specify the behavior which deviates from the norm.

But I suspect that this is not how Mockito wants me to set up mock behaviors, because when I tried to verify that a failure in ServiceB means that ServiceC is never hit, I realized that my calls to when(serviceC.doSomething()) in the @Before counted as invocations on serviceC. That is, my verifyZeroInteractions(serviceC) always failed because I had called when(serviceC.doSomething()).thenReturn(true), even when the test case never touched serviceC otherwise.

So what is the best practice? Am I better off just explicitly setting up the behavior for every mock in every test, even though I'd be repeating nearly the same 5 lines all over the place?

Answer 1

when(serviceC.doSomething()) in the @Before counted as invocations on serviceC

I doubt that the when construct is treated as an invocation because that is just stubbing.
Can you double check your code to see whether serviceC.doSomething is called from within your @Test

Regarding the best practice, I think you should only move in stubbing behaviour which is common for all test cases into @Before

As an aside from the way your code is looking I think you can try refactoring into Chain of Responsibility pattern and this should help you in coding the test code.