[Enhancement request]: void methods should require corresponding strict setup or an explicit verification

[Ashley Waldron]

Currently it's possible that mocked void methods could be called with the wrong parameters but the test would still pass if no mock setups/verifications have been added.

I think that if a mocked void method is called (with strict mode turned on) then Mockito should fail the test if it does not contain at least one of the following:

1. An explicit doNothing() setup call at the start of the test for each mocked void method that was called.
2. An explicit verify() call at the end of the test for each mocked void method that was called.

For example, If I have the following code:

    public Result doSomeAction(Request request) {
        someExternalClass.someVoidMethod(request);
        Result result = new Result();
        // setSomeStuff on Result object
        return result;
    }

And I have the following test for that code:

    @Test
    void doSomeActionSuccess() {
        Request testRequest = setupTestRequest();
        Result result =  classUnderTest.doSomeAction(testRequest);
       
        // Some assertions here
    }

Then this test will pass even though I haven't verified that the mocked 'someExternalClass.someVoidMethod()' was called with the correct parameters.

This isn't usually as much of a concern for mocked non-void methods because if they are called without a setup then they will return null which has a greater chance of causing problems during the test run that a developer would spot and fix (although that's by no means guaranteed).

I think that if void methods are called (with strict stubbing turned on), like the example above then it should require the test to contain at least one of the following:

1. doNothing().when(someExternalClass).someVoidMethod(testRequest);
   
2. verify(someExternalClass).someVoidMethod(testRequest);