function message() {
        if (options.passed) {
          return 'Passed.';
        } else if (options.message) {
          return options.message;
        } else if (options.error) {
          return exceptionFormatter.message(options.error);
        }
        return '';
      }
@typedef Expectation
@property {String} matcherName - The name of the matcher that was executed for this expectation.
@property {String} message - The failure message for the expectation.
@property {String} stack - The stack trace for the failure if available.
@property {Boolean} passed - Whether the expectation passed or failed.
@property {Object} expected - If the expectation failed, what was the expected value.
@property {Object} actual - If the expectation failed, what actual value was produced.
@property {String|undefined} globalErrorType - The type of an error that
is reported on the top suite. Valid values are undefined, "afterAll",
"load", "lateExpectation", and "lateError".