I am continually amazed about the basic and obvious things that are picked up in code review, even for experienced developers.

I have been using Mockito for a number of years and its a great mocking framework. Every now and again I want to write a test like this

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@Test
public void example_1() {
	setupPresenter(null);

	// act
	presenter.editTrackName(1);

	// assert
	Mockito.verify(mockview, Mockito.times(1)).promptForTrackName("1", Mockito.anyString());
}

I want to check that the first parameter passed to the promptForTrackName method is the string “1”. I either genuinely do not care what the second parameter is or if its legacy code the second parameter is unpredictable. I know its not ideal but we dont always get to control the structure of code as much as we would want.

If I were to write a test like this in Mockito 2 I would get this error when the test is run

org.mockito.exceptions.misusing.InvalidUseOfMatchersException: 
Invalid use of argument matchers!
2 matchers expected, 1 recorded:
-> at com.andrewandderek.trailblazer.unittests.ui.tracklist.ExampleTests.example_1(ExampleTests.java:35)

This exception may occur if matchers are combined with raw values:
    //incorrect:
    someMethod(anyObject(), "raw String");
When using matchers, all arguments have to be provided by matchers.
For example:
    //correct:
    someMethod(anyObject(), eq("String by matcher"));

For more info see javadoc for Matchers class.

This error message is great and tells me exactly how to correct this. However older versions of Mockito the error message was not as good and it just said that I should make all the parameters any() or none.

So I could use captors to example each parameter or if I was lazy do this

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@Test
public void example_2() {
	setupPresenter(null);

	// act
	presenter.editTrackName(1);

	// assert
	Mockito.verify(mockview, Mockito.times(1)).promptForTrackName(Mockito.anyString(), Mockito.anyString());
}

This worked but was not as good a test. I knew not to try the other test so I never saw the new error message.

Recently in a code review someone pointed out that I could simply do as the error message suggested and rewrite my test like this

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public void example_3() {
	setupPresenter(null);

	// act
	presenter.editTrackName(1);

	// assert
	Mockito.verify(mockview, Mockito.times(1)).promptForTrackName(eq("1"), Mockito.anyString());
}

I did feel slightly foolish but I am glad to heave learnt a new trick - thanks Karl.