How do I assert my exception message with JUnit Test annotation?

Question

I have written a few JUnit tests with @Test annotation. If my test method throws a checked exception and if I want to assert the message along with the exceptio

Answer 1

I like user64141's answer but found that it could be more generalized. Here's my take:

public abstract class ExpectedThrowableAsserter implements Runnable {

    private final Class throwableClass;
    private final String expectedExceptionMessage;

    protected ExpectedThrowableAsserter(Class throwableClass, String expectedExceptionMessage) {
        this.throwableClass = throwableClass;
        this.expectedExceptionMessage = expectedExceptionMessage;
    }

    public final void run() {
        try {
            expectException();
        } catch (Throwable e) {
            assertTrue(String.format("Caught unexpected %s", e.getClass().getSimpleName()), throwableClass.isInstance(e));
            assertEquals(String.format("%s caught, but unexpected message", throwableClass.getSimpleName()), expectedExceptionMessage, e.getMessage());
            return;
        }
        fail(String.format("Expected %s, but no exception was thrown.", throwableClass.getSimpleName()));
    }

    protected abstract void expectException();

}

Note that leaving the "fail" statement within the try block causes the related assertion exception to be caught; using return within the catch statement prevents this.