source.put("NestedMap", nested);

        Map<String, Object> result = searchLogHelper.toLowerHyphen(source);

        assertEquals("value1", result.get("test_key"));
        assertEquals("value2", result.get("another_test_key"));

        @SuppressWarnings("unchecked")
        Map<String, Object> nestedResult = (Map<String, Object>) result.get("nested_map");