A better eq() when matching method arguments with Mockito

George Georgovassilis java, junit, testing 03 Jun 201217 Dec 2019

I learned late of Mockito [1], even so more I love it. Walking a little farther away from the basics, a frequent needs presents itself to match method parameters (either when specifying or verifying behaviour) based on properties of complex objects which do not implement the java equals contract.

Such an example would be verifying that an order is passed to a checkout method which contains a certain confirmation email address:

verify(orderService).dispatchOrder(withEmail(order,"test@example.com"));

Hamcrest matchers and generics to our rescue:

static  T withEmail(final T model, final String email){

    BaseMatcher m = new BaseMatcher() {

 @Override
        public boolean matches(Object o) {
            if (!(o instanceof HasEmail))
                return false;
            return ((HasEmail)o).getEmail().equals(email);
        }

        @Override
        public void describeTo(Description arg) {
        }
    };

    return Mockito.argThat(m);
}