The Javadoc gives this example for the matches method:
assertThat(player).matches(p -> p.isRookie());
And indeed, when I define a dummy class Player, the above statement compiles ok. However, when I define a class that derives from Exception, then the following doesn't compile:
public class MyCustomException extends Exception {
public boolean isMyCustomFieldSet() { return true; }
}
...
MyCustomException myCustomException = new MyCustomExcpetion();
assertThat(myCustomException).matches(e -> e.isMyCustomFieldSet());
I can make it compile by using a cast:
assertThat(myCustomException).matches(e -> ((MyCustomException)e).isMyCustomFieldSet());
but that cast looks "ugly" and a bit of a hack to work around some sort of deficiency. Can I make it compile in a "nicer" way, i.e. without using a cast?
The issue is in Assertions, it declares AbstractThrowableAssert<?, ? extends Throwable> assertThat(Throwable t) instead of <T> AbstractThrowableAssert<?, T extends Throwable> assertThat(T t)
But unfortunately this can not be done because of the following existing method that clashes with it: public static <T> ObjectAssert<T> assertThat(T actual).
Casting is a solution, I agree it is not super elegant.
What I would do in that case is simply:
assertThat(myCustomException.isMyCustomFieldSet()).isTrue();
or to keep assertions on myCustomException directly:
assertThat(myCustomException).hasFieldOrPropertyWithValue("myCustomFieldSet", true)
.hasFieldOrPropertyWithValue("myOtherField", "foo");
The drawback here is accessing fields by name which is not refactoring friendly.