Question

Trying to figure out how to write a custom matcher for a primitive value. Say I’ve got the following custom matcher:

class IsEven extends ArgumentMatcher<Integer> {
    public boolean matches(Object i) {
        return ((Integer) i) % 2 == 0;
    }
}

And I run the following test. ‘mocked’ is an already-mocked instance of a class that has a method ‘someMethod’:

@Test
public void primatives() {

    mocked.someMethod(2);

    ArgumentMatcher<Integer> customMatcher = new IsEven();

    // ! Throws NPE !
    Mockito.verify(mocked).someMethod(Mockito.argThat(customMatcher));

}

The reason for the NullPointerException is that the Mockio.argThat method always returns a null, which I’m guessing cannot be autoboxed back into an integer.

I feel as though this woudl be a common use case – any advice?

Thanks,
Roy

Answer 1

.. Reading Javadoc helps:

In rare cases when the parameter is a primitive then you must use relevant intThat(), floatThat(), etc. method. This way you will avoid NullPointerException during autounboxing.