code: function doesMatch(_ref2) {
      var matcher = _ref2.matcher;
      var err = _ref2.err;
  
      if (typeof matcher === 'string') {
        return err.message.indexOf(matcher) > -1;
      }
      if (matcher instanceof RegExp) {
        return matcher.test(err.message);
      }
      if (typeof matcher === 'function') {
        return matcher(err);
      }
      if (matcher.constructor === Error.constructor) {
        return err instanceof matcher;
      }
      throw new Error(UNRECOGNISED_MATCHER_ERR);
    }
docs: Determine if the given `err` satisfies the criteria defined by `matcher`:
  - if `matcher` is a String, expect the error message to contain `matcher`
  - if `matcher` is a RegExp, match the error message against it
  - if `matcher` is a Function, call the function with `err` and return the result
  - if `matcher` is an Error, expect their constructors to be the same
  @param {Object} matcher error matcher
  @param {Error} err error to match against
  @returns {Boolean}