我应该如何处理自定义 Hamcrest 匹配器中的异常？

Question

I am using JUnit and Hamcrest to do some automated testing. To make my tests more readable I want to make a custom matcher however the code that I am calling in the matchesSafely method might throw exceptions. I am unsure of how to handle such exceptions as the method signature for matchesSafely does not allow for throwing exceptions.

An example for illustration:

public static Matcher<Session> hasObjectOfType(final Class<?> cls) {
    return new TypeSafeMatcher<Session>() {
        /* describeTo method skipped for brevity */
        protected boolean matchesSafely(Session session) {
            return session.provideList(cls.getName()).iterator().hasNext();
        }
    }
}

So what happens here is that session.provideList declares a checked exception and I need to handle that somehow. I see two possible ways of handling this but maybe I'm overlooking something:

1. Catch the checked exception and wrap it in a runtime exception which is then thrown.
2. Catch the checked exception and return false. In reality I'm using a TypeSafeDiagnosingMatcher so a concern here is that the mismatch description should then (probably?) be different for the two possible scenarios: an empty list or a thrown exception.

In any case which would be the best practice way of handling exceptions?

Answer 1

You want to be able to debug failing tests as quickly as possible. Thus: you should prefer option 1.

Because in that case, your "enclosing" test will fail on that runtime exception; and it will print the exception content to you. So you know where and why your test failed.

Compare that to: silently turning the exception into "false"; and ending up with assertThat telling you that your match failed. Maybe you could manage to give a meaningful message in the end; but still: you would have to put in some "energy" go get there. Option 1 comes for free - try/catch rethrow.

So, my advise: go for option 1 - and see how it works for you. If that is not "good enough" for some reason; then invest more time and see if option 2 somehow would improve things.