function expectReturn( pass, errorMsg, vsMsg = null ) {
    const negativeErrorMsg = vsMsg || errorMsg.replace( " expected ", " not expected " );
    return {
      message: () => normalizeMessage( pass ? negativeErrorMsg : errorMsg ),
      pass
    };
  }
Helper
@param {Boolean} pass
@param {String} errorMsg
@param {String} [vsMsg]
@returns {Object}