How to check if exception's cause matches a type of exception

Question

I have this code:

CompletableFuture<SomeClass> future = someInstance.getSomething(-902);
try {
    future.get(15, TimeUnit.SECONDS);
    fail("Print some error");
} catch (InterruptedException e) {
    e.printStackTrace();
} catch (ExecutionException e) {
    // Here I want to check if e.getCause() matches some exception
} catch (TimeoutException e) {
    e.printStackTrace();
}

So when a ExecutionException is thrown, it is thrown by another exception in another class. I want to check if the original exception that cause ExecutionException matches some custom exception that I created. How do I achieve that with JUnit?

Answer 1

Use ExpectedException like this:

@Rule
public final ExpectedException expectedException = ExpectedException.none();

@Test
public void testExceptionCause() throws Exception {
    expectedException.expect(ExecutionException.class);
    expectedException.expectCause(isA(CustomException.class));

    throw new ExecutionException(new CustomException("My message!"));
}