// Should be allowed again
        assertTrue(rateLimiter.checkAttempt("user7", ip), "Should be allowed after manual unblock");
    }

    @Test
    public void testNullUsername() throws Exception {
        // Null username should be handled gracefully
        assertTrue(rateLimiter.checkAttempt(null, "192.168.1.8"), "Null username should be allowed");

        // Should not affect IP limiting