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() {

    }

    @Test
    @DisplayName("Test log authentication success")
    void testLogAuthentication() {
        logger.logAuthentication(true, "testuser", "DOMAIN", "192.168.1.1");

        Map<EventType, Long> stats = logger.getStatistics();
        assertEquals(Long.valueOf(1), stats.get(EventType.AUTHENTICATION_SUCCESS), "Should have 1 authentication event");
    }

    @Override
    public void setUp() throws Exception {
        super.setUp();
        testEnv = new Hashtable<>();
        testEnv.put("test.key", "test.value");
        ldapUser = new LdapUser(testEnv, "testuser");

        ComponentUtil.register(new SystemHelper(), "systemHelper");

        // Register a mock LdapManager to avoid NPE
        ComponentUtil.register(new LdapManager() {

        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());
    }

    /**
     * Creates a Type-3 message using default values from the current
     * environment.
     */
    public Type3Message() {
        setFlags(getDefaultFlags());
        setDomain(getDefaultDomain());
        setUser(getDefaultUser());
        setWorkstation(getDefaultWorkstation());
    }

    /**
     * Creates a Type-3 message in response to the given Type-2 message
     * using default values from the current environment.

        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

        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
     */

        // Given
        Type2Message type2 = createMockType2Message();
        String password = "testpassword";
        String domain = "TESTDOMAIN";
        String username = "testuser";
        String workstation = "TESTWS";
        int flags = NtlmFlags.NTLMSSP_NEGOTIATE_UNICODE | NtlmFlags.NTLMSSP_NEGOTIATE_NTLM;

        // When

	ctx, cancel := context.WithTimeout(context.Background(), testDefaultTimeout)
	defer cancel()

	// 1. Create a user.
	accessKey, secretKey := mustGenerateCredentials(c)
	err := s.adm.SetUser(ctx, accessKey, secretKey, madmin.AccountEnabled)
	if err != nil {
		c.Fatalf("Unable to set user: %v", err)
	}

	// 2. Check new user appears in listing
	usersMap, err := s.adm.ListUsers(ctx)
	if err != nil {