junit assert in thread throws exception

Question

What am I doing wrong that an exception is thrown instead of showing a failure, or should I not have assertions inside threads?

 @Test
 public void testCompl         


        

Answer 1

A small improvement to Eyal Schneider's answer:
The ExecutorService allows to submit a Callable and any thrown Exceptions or Errors are rethrown by the returned Future.
Consequently, the test can be written as:

@Test
public void test() throws Exception {
  ExecutorService es = Executors.newSingleThreadExecutor();
  Future future = es.submit(() -> {
    testSomethingThatMightThrowAssertionErrors();
    return null;
  });

  future.get(); // This will rethrow Exceptions and Errors as ExecutionException
}