def get_dict_differences(ref_json, test_json, ref_file, test_file):
    """
    Identify differences between the two JSON dictionaries.

    Parameters
    ----------
    ref_json : dict
        Refernce JSON configuration dictionary.
    test_json : dict
        Test JSON configuration dictionary.
    ref_file : str
        Name of reference configuration file.
    test_file : str
        Name of test configuration file.

    Returns
    -------
    result : list of str
        List containing comparison results.
    """
    result = ["REF: {}, TEST: {}".format(ref_file, test_file)]
    for key in ref_json:
        if key not in test_json:
            result.append("Field {} not specified in test json".format(key))
        elif ref_json[key] and test_json[key] is not None:
            result.append("Field {} is set to None in test json and to {} "
                          "in reference file".format(key, ref_json[key]))
        elif ref_json[key] is not None and test_json[key]:
            result.append("Field {} is set to None in reference json and to {} "
                          "in test file".format(key, test_json[key]))
        elif not ref_json[key] == test_json[key]:
            result.append("Field {} has different value in test json {} "
                          "vs {}".format(key, ref_json[key], test_json[key]))
    added_fields = set(test_json.keys()).difference(set(ref_json.keys()))
    if len(added_fields) > 0:
        result.append("The following extra fields are present "
                      "in test json: {}".format(', '.join(added_fields)))

    return result