How to use notifyListeners method of org.mockito.internal.verification.DummyVerificationMode class

You should not mock the classes and methods you are testing. You should only mock methods that are needed to perform the test itself.

For example, if you need some objects from a web service to perform a test, you could mock the web service calls, so you don't need to actually call the web service.

You need to provide a way of accessing the member variables so you can pass in a mock (the most common ways would be a setter method or a constructor which takes a parameter).

If your code doesn't provide a way of doing this, it's incorrectly factored for TDD (Test Driven Development).

Roughly speaking, a then-block may only contain assertions in the form of boolean expressions. A Mockito verification expression doesn't fit this contract, as it will return a falsy value (null, false, 0) when it passes, which is interpreted as a failed assertion by Spock.

To solve this problem, you can either write a helper method that wraps around the verification expressions and always returns true, or you can use Spock's built-in mocking framework instead of Mockito.

Make sure you add @RunWith(PowerMockRunner.class) to the top of your class as well.

::edit:: two years later...

Don't ever use PowerMockito, you shouldn't need to.

If you do need to, you have most likely broken the SOLID principles and your design is wrong.

Fix your design instead.

I wouldn't use exceptions to test that, but verifications. And another problem is that you can't use when() with methods returning void.

Here's how I would do it:

FizzConfigurator fixture = Mockito.spy(new FizzConfigurator());
doNothing().when(fixture).doWidget(Mockito.anyString(), Mockito.<Config>any()));
fixture.doBuzz("some string");
Mockito.verify(fixture).doWidget("some string", Config.SOMETIMES);

You are using mockito anyString() while calling the test method, it should be used only for verifying a mock object to ensure a certain method is called with any string parameter inside the test, but not to invoke the test itself. For your test use empty string "" instead to anyString().

You can use a Mock reponse or an actual response and then use when, e.g.:

Page<Company> companies = Mockito.mock(Page.class);
Mockito.when(companyRepository.findAllByIsActiveTrue(pageable)).thenReturn(companies);

Or, just instantiate the class:

List<Company> companies = new ArrayList<>();
Page<Company> pagedResponse = new PageImpl(companies);
Mockito.when(companyRepository.findAllByIsActiveTrue(pagedResponse)).thenReturn(pagedResponse);

To test the lambdas behavior, the underlayingApi has to be mocked where the lambda is invoked via the InvoactionOnMock object like this.

    `when`(underlayingApi.post(eq("some/rest/url"),
                               any())).thenAnswer {
        val argument = it.arguments[1]
        val completion = argument as ((rawResult: String?, exception: Exception?) -> Unit)
        completion.invoke("result", null)
    }

This leads to the invocation of the callback within the object under test. Now to check if the callback out of the object under test is working verify it like that.

    objUnderTest.loadData(id,
                          { json, exception ->
                              assert....
                          })

In this case do I need to write a captor for each argument in spite of the fact I need to capture only the first argument?

durron597's answer is correct—you do not need to capture all arguments if you want to capture one of them. One point of clarification, though: a call to ArgumentCaptor.capture() counts as a Mockito matcher, and in Mockito if you use a matcher for any method argument you do have to use a matcher for all arguments.

For a method yourMock.yourMethod(int, int, int) and an ArgumentCaptor<Integer> intCaptor:

/*  good: */  verify(yourMock).yourMethod(2, 3, 4);  // eq by default
/*  same: */  verify(yourMock).yourMethod(eq(2), eq(3), eq(4));

/*   BAD: */  verify(yourMock).yourMethod(intCaptor.capture(), 3, 4);
/* fixed: */  verify(yourMock).yourMethod(intCaptor.capture(), eq(3), eq(4));

These also work:

verify(yourMock).yourMethod(intCaptor.capture(), eq(5), otherIntCaptor.capture());
verify(yourMock).yourMethod(intCaptor.capture(), anyInt(), gt(9000));