Mockito match any class argument

Question

Two more ways to do it (see my comment on the previous answer by @Tomasz Nurkiewicz):

The first relies on the fact that the compiler simply won't let you pass in something of the wrong type:

when(a.method(any(Class.class))).thenReturn(b);

You lose the exact typing (the Class<? extends A>) but it probably works as you need it to.

The second is a lot more involved but is arguably a better solution if you really want to be sure that the argument to method() is an A or a subclass of A:

when(a.method(Matchers.argThat(new ClassOrSubclassMatcher<A>(A.class)))).thenReturn(b);

Where ClassOrSubclassMatcher is an org.hamcrest.BaseMatcher defined as:

public class ClassOrSubclassMatcher<T> extends BaseMatcher<Class<T>> {

    private final Class<T> targetClass;

    public ClassOrSubclassMatcher(Class<T> targetClass) {
        this.targetClass = targetClass;
    }

    @SuppressWarnings("unchecked")
    public boolean matches(Object obj) {
        if (obj != null) {
            if (obj instanceof Class) {
                return targetClass.isAssignableFrom((Class<T>) obj);
            }
        }
        return false;
    }

    public void describeTo(Description desc) {
        desc.appendText("Matches a class or subclass");
    }       
}

Phew! I'd go with the first option until you really need to get finer control over what method() actually returns :-)

There is another way to do that without cast:

when(a.method(Matchers.<Class<A>>any())).thenReturn(b);

This solution forces the method any() to return Class<A> type and not its default value (Object).

If you have no idea which Package you need to import:

import static org.mockito.ArgumentMatchers.any;
any(SomeClass.class)

OR

import org.mockito.ArgumentMatchers;
ArgumentMatchers.any(SomeClass.class)

How about:

when(a.method(isA(A.class))).thenReturn(b);

or:

when(a.method((A)notNull())).thenReturn(b);

the solution from millhouse is not working anymore with recent version of mockito

This solution work with java 8 and mockito 2.2.9

where ArgumentMatcher is an instanceof org.mockito.ArgumentMatcher

public class ClassOrSubclassMatcher<T> implements ArgumentMatcher<Class<T>> {

   private final Class<T> targetClass;

    public ClassOrSubclassMatcher(Class<T> targetClass) {
        this.targetClass = targetClass;
    }

    @Override
    public boolean matches(Class<T> obj) {
        if (obj != null) {
            if (obj instanceof Class) {
                return targetClass.isAssignableFrom( obj);
            }
        }
        return false;
    }
}

And the use

when(a.method(ArgumentMatchers.argThat(new ClassOrSubclassMatcher<>(A.class)))).thenReturn(b);

None of the examples above worked for me, as I'm required to mock one method multiple times for different class type parameters.

Instead, this works.

//Handle InstrumentType.class
Mockito.doReturn(new InstrumentTypeMapper() {
    @Override
    public InstrumentType map(String sourceType) throws Exception {
        return InstrumentType.Unknown;
    }
}).when(mappingLoader).load(any(ServiceCode.class), argThat(new ArgumentMatcher<Class<InstrumentType>>() {
    @Override
    public boolean matches(Class<InstrumentType> argument) {
        return InstrumentType.class.isAssignableFrom(argument);
    }
}));

//Handle InstrumentSubType.class    
Mockito.doReturn(new InstrumentSubTypeMapper() {
    @Override
    public InstrumentSubType map(String sourceType) throws Exception {
        return InstrumentSubType.istNone;
    }
}).when(mappingLoader).load(any(ServiceCode.class), argThat(new ArgumentMatcher<Class<InstrumentSubType>>() {
    @Override
    public boolean matches(Class<InstrumentSubType> argument) {
        return InstrumentSubType.class.isAssignableFrom(argument);
    }
}));

This is the short version:

Mockito.doReturn(new InstrumentTypeMapper() {
    @Override
    public InstrumentType map(String sourceType) throws Exception {
        return InstrumentType.Unknown;
    }
}).when(mappingLoader).load(any(ServiceCode.class), argThat((ArgumentMatcher<Class<InstrumentType>>) InstrumentType.class::isAssignableFrom));

Mockito.doReturn(new InstrumentSubTypeMapper() {
    @Override
    public InstrumentSubType map(String sourceType) throws Exception {
        return InstrumentSubType.istNone;
    }
}).when(mappingLoader).load(any(ServiceCode.class), argThat((ArgumentMatcher<Class<InstrumentSubType>>) InstrumentSubType.class::isAssignableFrom));

As you can see, I'm using custom ArgumentMatchers together with argThat, not sure if there is a shorter way that also works.