Misleading behavior of Mockito.verifyZeroInteractions()

[mockitoguy]

Problem

Mockito.verifyZeroInteractions() actually does not do what it advertises. The purpose of this ticket is to discuss whether to change the behavior of this method in Mockito 3.

Details

Based on user feedback at #977, from @ffissore, "verifyZeroInteractions" API can be misleading. When you read that method in test code, you expect zero interactions with specified mocks. However, "verifyZeroInteractions" is only an alias to "verifyNoMoreInteractions" and in fact, it does not guarantee that there were zero interactions. Let's use examples to illustrate the problem

Feedback needed

Please comment / vote / state your opinion about changing the behavior of "verifyZeroInteractions" so that it actually ensures that there were zero interactions with the mock (regardless if previously verified or not).

Examples

Below examples illustrate current behavior of Mockito 2.x, in case you are puzzled what this ticket is about.

Example 1 - verifyNoMoreInteractions

mock.foo();
verify(mock).foo();
verifyNoMoreInteractions(mock); //pretty clear I think

Example 2 - verifyZeroInteractions

mock.foo();
verify(mock).foo();

verifyZeroInteractions(mock);
//above passes because verifyZeroInteractions == verifyNoMoreInteractions
//and we already have verified the only method invoked on the mock

Example 3 - verifyZeroInteractions with regular stubbing

given(mock.foo()).willReturn("x");
assertEquals("x", mock.foo());
verify(mock).foo();

verifyZeroInteractions(mock);
//above passes because verifyZeroInteractions == verifyNoMoreInteractions

Example 4 - verifyZeroInteractions with new strict stubbing

given(mock.foo()).willReturn("x");
assertEquals("x", mock.foo());

verifyZeroInteractions(mock);
//above passes because with strict stubbing
//stubbed method are implicitly verified when they are "used"
//this is one of key features of strict stubbing (DRY, don't repeat yourself)

[TimvdLippe]

This was fixed in #989