public void test_constructor() {
        AuthenticationManager manager = new AuthenticationManager();
        assertNotNull(manager);
    }

    // Test insert with no chains
    @Test
    public void test_insert_noChains() {
        User user = createTestUser("testuser");
        authenticationManager.insert(user);
        // Should not throw exception even with no chains
    }

    // Test insert with single chain
    @Test