In Java how can I validate a thrown exception with JUnit?

Question

When writing unit tests for a Java API there may be circumstances where you want to perform more detailed validation of an exception. I.e. more than is offered by the @t

Answer 1

In JUnit 4 it can be easily done using ExpectedException rule.

Here is example from javadocs:

// These tests all pass.
public static class HasExpectedException {
    @Rule
    public ExpectedException thrown = ExpectedException.none();

    @Test
    public void throwsNothing() {
        // no exception expected, none thrown: passes.
    }

    @Test
    public void throwsNullPointerException() {
        thrown.expect(NullPointerException.class);
        throw new NullPointerException();
    }

    @Test
    public void throwsNullPointerExceptionWithMessage() {
        thrown.expect(NullPointerException.class);
        thrown.expectMessage("happened?");
        thrown.expectMessage(startsWith("What"));
        throw new NullPointerException("What happened?");
    }
}