v3(),
                (oldV, newV) -> {
                  assertEquals(v0(), oldV);
                  assertEquals(v3(), newV);
                  return null;
                }));
    expectMissing(e0());
  }

  public void testMergeNullValue() {
    try {
      getMap()
          .merge(
              k0(),
              null,
              (oldV, newV) -> {

                v3(),
                (oldV, newV) -> {
                  assertEquals(v0(), oldV);
                  assertEquals(v3(), newV);
                  return null;
                }));
    expectMissing(e0());
  }

  public void testMergeNullValue() {
    try {
      getMap()
          .merge(
              k0(),
              null,
              (oldV, newV) -> {

        // Test deeply nested exception causes
        Exception level3 = new Exception("Level 3: Database connection failed");
        Exception level2 = new Exception("Level 2: User lookup failed", level3);
        Exception level1 = new Exception("Level 1: Authentication service error", level2);
        SsoProcessException topLevel = new SsoProcessException("SSO process failed", level1);

        // Verify the chain

    }

    public void test_register_entitySet() {
        RenderData data = new RenderData();

        BsUser entity1 = new BsUser();
        entity1.setName("name1");

        BsUser entity2 = new BsUser();
        entity2.setName("name2");

        Set<BsUser> entitySet = new HashSet<>();
        entitySet.add(entity1);
        entitySet.add(entity2);

        assertEquals(message, exception.getMessage());
        assertEquals(cause, exception.getCause());
    }

    public void test_constructor_withCause() {
        // Test constructor with cause only
        Throwable cause = new IllegalArgumentException("Cause exception");
        FessSystemException exception = new FessSystemException(cause);

        DictionaryExpiredException original = new DictionaryExpiredException();

        // Serialize
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        ObjectOutputStream oos = new ObjectOutputStream(baos);
        oos.writeObject(original);
        oos.close();

        // Deserialize
        ByteArrayInputStream bais = new ByteArrayInputStream(baos.toByteArray());

    }

    public void test_nestedCause() {
        // Test with nested exceptions
        RuntimeException rootCause = new RuntimeException("Root cause");
        ParseException parseException = new ParseException("Parse error");
        parseException.initCause(rootCause);
        QueryParseException queryParseException = new QueryParseException(parseException);

        assertEquals(parseException, queryParseException.getCause());

        // Test OK status
        ApiResult okResult = new ApiResult.ApiResponse().status(Status.OK).result();
        assertNotNull(okResult);

        // Test BAD_REQUEST status
        ApiResult badRequestResult = new ApiResult.ApiResponse().status(Status.BAD_REQUEST).result();
        assertNotNull(badRequestResult);

        // Test UNAUTHORIZED status

        RequestParameter param = new RequestParameter(name, values);

        assertEquals("", param.getName());
        assertNotNull(param.getValues());
        assertEquals(2, param.getValues().length);
    }

    public void test_constructor_withNullValues() {
        // Test with null values array
        String name = "paramName";
        RequestParameter param = new RequestParameter(name, null);

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

    public void test_constructor_withLongUsername() {
        // Test with a very long username
        String username = "verylongusername".repeat(10);
        FessUserNotFoundException exception = new FessUserNotFoundException(username);