assertEquals("AuthenticationDao returned null, which is an interface contract violation",
assertEquals("UserDetailsService returned null, which is an interface contract violation",
    public void testDetectsNullBeingReturnedFromAuthenticationDao() {        UsernamePasswordAuthenticationToken token = new UsernamePasswordAuthenticationToken("marissa", "koala");        DaoAuthenticationProvider provider = new DaoAuthenticationProvider();        provider.setUserDetailsService(new MockAuthenticationDaoReturnsNull());        try {            provider.authenticate(token);            fail("Should have thrown AuthenticationServiceException");        } catch (AuthenticationServiceException expected) {            assertEquals("AuthenticationDao returned null, which is an interface contract violation",                expected.getMessage());        }    }