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
    public void test_insert_singleChain() {
        User user = createTestUser("testuser");
        TestAuthenticationChain chain = new TestAuthenticationChain();

        testFessConfig.ldapAdminSyncPassword = false;

        boolean result = ldapChain.changePassword("testuser", "newpassword");

        assertFalse(result); // returns !changed || syncPassword = !true || false = false
        assertEquals("testuser", testLdapManager.changePasswordUsername);
        assertEquals("newpassword", testLdapManager.changePasswordPassword);

    public void test_constructor_withValidUsername() {
        // Test with a normal username
        String username = "testuser";
        FessUserNotFoundException exception = new FessUserNotFoundException(username);

        assertNotNull(exception);
        assertEquals("User is not found: testuser", exception.getMessage());
        assertNull(exception.getCause());
    }

    public void test_constructor_withEmptyUsername() {

    @BeforeEach
    void setUp() throws CIFSException {
        Properties props = new Properties();
        // Set some default test properties
        props.setProperty("jcifs.smb.client.username", "testuser");
        props.setProperty("jcifs.smb.client.password", "testpass");
        props.setProperty("jcifs.smb.client.domain", "testdomain");
        props.setProperty("jcifs.netbios.hostname", "testhost");

        chain.changePasswordResult = true;

        boolean result = chain.changePassword("testuser", "newpassword123");

        assertTrue(result);
        assertEquals(1, chain.changePasswordCalls.size());
        assertEquals("testuser", chain.changePasswordCalls.get(0).getKey());
        assertEquals("newpassword123", chain.changePasswordCalls.get(0).getValue());
    }

        principalVector.add(new DERTaggedObject(0, new ASN1Integer(1))); // name-type
        ASN1EncodableVector nameVector = new ASN1EncodableVector();
        nameVector.add(new DERGeneralString("testuser"));
        principalVector.add(new DERTaggedObject(1, new DERSequence(nameVector)));
        vector.add(new DERTaggedObject(3, new DERSequence(principalVector)));

        char[] testPassword = "DomainPass321!".toCharArray();
        NtlmPasswordAuthenticator auth = new NtlmPasswordAuthenticator("DOMAIN", "testuser", testPassword);

        assertEquals("DOMAIN", auth.getUserDomain());
        assertEquals("testuser", auth.getUsername());
        assertEquals(new String(testPassword), auth.getPassword());
    }

    /**
     * Test null password handling
     */

        for (int i = 0; i < 100; i++) {
            NtlmPasswordAuthenticator auth1 = new NtlmPasswordAuthenticator("testdomain", "testuser", "password123");
            NtlmPasswordAuthenticator auth2 = new NtlmPasswordAuthenticator("testdomain", "testuser", "password124");
            auth1.equals(auth2);
        }
    }

    /**
     * Test that password comparison is constant-time by comparing execution times

    public void test_matches() throws Exception {
        FtpAuthentication auth = new FtpAuthentication();
        auth.setServer("hostname");
        auth.setPort(21);
        auth.setUsername("testuser");
        auth.setPassword("testpass");

        assertTrue(auth.matches("ftp://hostname:21/test/aaa.html"));
        assertTrue(auth.matches("ftp://hostname/test/aaa.html"));

        mockAuth.username = "testuser";
        mockAuth.domain = "TESTDOMAIN";
        mockAuth.password = "testpass";

        when(mockAuth.getAnsiHash(any(byte[].class))).thenReturn(new byte[24]);
        when(mockAuth.getUnicodeHash(any(byte[].class))).thenReturn(new byte[24]);
        when(mockAuth.getName()).thenReturn("testuser");
        when(mockAuth.getDomain()).thenReturn("TESTDOMAIN");