assertEquals("Y1", dataMap.get("y"));
    }

    /** Case 4: Both baseKey and baseKey.overwrite exist → Overwrite with the value of .overwrite */
    @Test
    public void test_mergeResponseData_baseAndOverwrite() {
        Map<String, Object> dataMap = new HashMap<>();
        Map<String, Object> responseDataMap = new HashMap<>();
        responseDataMap.put("z", "Z0");
        responseDataMap.put("z.overwrite", "Z1");