}

    // Test toString method
    public void test_toString() {
        String result = charMappingFile.toString();
        assertTrue(result.contains("MappingFile"));
        assertTrue(result.contains("path=" + testFile.getAbsolutePath()));
        assertTrue(result.contains("id=test_id"));
    }

    // Test get method with empty file

        if (indexMappings == null || !indexMappings.containsKey("properties")) {
            String source = null;
            final String mappingFile = getResourcePath(indexConfigPath, fessConfig.getFesenType(), "/" + index + "/" + docType + ".json");
            try {
                source = FileUtil.readUTF8(mappingFile);
                if (DOC_INDEX.equals(index)) {
                    for (final UnaryOperator<String> rule : docMappingRewriteRuleList) {