java - Custom hamcrest matcher that works with "not"? -

i have class (say, entity).

i want able

1. test instance of "valid", using custom code decide that
2. also test instance not valid, ideally using same code.

using maven, surefire, junit 4.11 (and hamcrest stuff shipped it).

so write class this

class isvalidentity extends typesafematcher<entity>{      @override public boolean matchessafely(entity e){        // , here bunch of asserts...        assertnotnull(e.id);        // etc.     }      @override     public void describeto(description description) {        description.appendtext("is valid entity");     }      @factory     public static <t> matcher<entity> validentity() {         return new isvalidentity();     }  } 

ok, fine, can do

assertthat(entity, is(validentity());  

in junit test, peachy.

but can't do

assertthat(entity, not(validentity()); 

because validentity fails broken asserts, while not guess should return false.

clearly i'm doing backwards here i'm not sure what's clever way of doing these custom matchers. or maybe shouldn't using typesafematcher @ doing different?

your matchessafely method should rewritten avoid throwing assertion failures. instead, perform checks manually , return false if necessary.

then, can negate in manner desire without consequence.