.setLevel(Level.ERROR)
                .setMessage(new SimpleMessage("test message 1"))
                .build();

        LogEvent event2 = Log4jLogEvent.newBuilder()
                .setLoggerName("another.logger.sub")
                .setLevel(Level.ERROR)
                .setMessage(new SimpleMessage("test message 2"))
                .build();

        assertEquals(3, events.size());
        assertEquals("error 1", events.get(0).getMessage());
        assertEquals("error 2", events.get(1).getMessage());
        assertEquals("error 3", events.get(2).getMessage());
    }

    @Test
    public void test_append_warnAppender_errorEvent() {

        // Messages should remain as provided
        assertEquals(message1, exception1.getMessage());
        assertEquals(message2, exception2.getMessage());

        // Messages should not be affected by cause
        assertFalse(exception1.getMessage().equals(exception2.getMessage()));
    }

    @Test
    public void test_longMessage() {
        // Test with very long message

        assertEquals("SSO process failed", topLevel.getMessage());
        assertEquals(level1, topLevel.getCause());
        assertEquals("Level 1: Authentication service error", topLevel.getCause().getMessage());
        assertEquals(level2, topLevel.getCause().getCause());
        assertEquals("Level 2: User lookup failed", topLevel.getCause().getCause().getMessage());

        assertEquals(originalException.getMessage(), deserializedException.getMessage());
        assertNotNull(deserializedException.getCause());
        assertEquals(originalException.getCause().getMessage(), deserializedException.getCause().getMessage());
    }

    @Test
    public void test_getMessage() {
        // Test getMessage() method
        String message = "Custom SSO error message";

        assertTrue(exception.getMessage().contains(cause.getClass().getName()));
        assertTrue(exception.getMessage().contains("Cause exception"));
    }

    @Test
    public void test_constructor_withNullMessage() {
        // Test constructor with null message
        FessSystemException exception = new FessSystemException((String) null);

        assertNull(exception.getMessage());
        assertNull(exception.getCause());

        assertNotSame(exception1, exception2);
        assertFalse(exception1.getMessage().equals(exception2.getMessage()));
        assertEquals("User is not found: user1", exception1.getMessage());
        assertEquals("User is not found: user2", exception2.getMessage());
    }

        assertTrue(exception instanceof FessSystemException);
    }

    @Test
    public void test_constructorWithNullMessage() {
        // Test constructor with null message
        SearchQueryException exception = new SearchQueryException((String) null);

        assertNull(exception.getMessage());
        assertNull(exception.getCause());

        assertEquals("Type1", exception1.getType());
        assertEquals("Message1", exception1.getMessage());
        assertEquals("Type2", exception2.getType());
        assertEquals("Message2", exception2.getMessage());

        assertNotSame(exception1, exception2);
    }

    @Test
    public void test_serialVersionUID() {

        ThemeException exception = new ThemeException(message, cause);

        assertNotNull(exception);
        assertEquals(message, exception.getMessage());
        assertEquals(cause, exception.getCause());
        assertEquals("Config file not found", exception.getCause().getMessage());
    }

    @Test
    public void test_constructorWithNullMessage() {
        // Test constructor with null message