Mockito anyString() vs any() – null handling

Sometimes, when I mock a method in Mockito, I used anyString instead of any and I get into a mess and my test fails. Why?

given(mUserRepo.getUser(anyString(). any())).willReturn(new User());

And what will happen if

mUserRepo.getUser(null);

UserRepo is called with null? Well, the matcher doesn’t work and the test fails. anyString() does not work with null values. If you pass null to a mocked service then use any() as a matcher.

How to mock a dynamic value returned from a method with Mockito?

Probably, most of you already know this, but it is good to keep it in mind when you want to dynamically change the values returned by a mock you have.

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Mockito verify input parameter was called with a given value

Edit 23.04.2018
According to this issue, Mockito cannot capture var-args still.

There is a very easy way to verify a method has been called with the right parameter in Mockito. All you need to do is use captors, to capture the actual argument. Here is how you can use them:

 
ArgumentCaptor argument = ArgumentCaptor.forClass(RuleEntity.class);
 verify(mRulesRepository).createRule(argument.capture());
 assertEquals(1,argument.getValue().getRules().get(0).getTriggers().size())

Simple it is, just a quick reminder for starters.