@Test
    public void test_insert_multipleChains() {
        User user = createTestUser("testuser");
        TestAuthenticationChain chain1 = new TestAuthenticationChain();
        TestAuthenticationChain chain2 = new TestAuthenticationChain();
        TestAuthenticationChain chain3 = new TestAuthenticationChain();

        authenticationManager.addChain(chain1);
        authenticationManager.addChain(chain2);

    public void test_delete_nullUser() {
        TestAuthenticationChain chain = new TestAuthenticationChain();

        chain.delete(null);

        assertEquals(1, chain.deleteCalls.size());
        assertNull(chain.deleteCalls.get(0));
    }

    // Test delete with multiple users
    @Test
    public void test_delete_multipleUsers() {
        TestAuthenticationChain chain = new TestAuthenticationChain();