UnhandledPromiseRejectionWarning

[andrewvsk]

Wrong Promise rejection implementation:

• https://github.com/CodeLenny/chai-events/blob/master/chai-events.js#L71
• https://github.com/CodeLenny/chai-events/blob/master/chai-events.js#L93

assert() just throws exception and DOESN'T reject Promise that we expect in out test.
In this case sometimes we see UnhandledPromiseRejectionWarning.

Case 1

  const eventEmitter = new EventEmitter();
  const onEventA = expect(eventEmitter).to.not.emit('eventA');
  eventEmitter.emit('eventA');  // <--- HERE we get exception from on() handler
  await onEventA;               //  NOT HERE !
});

Case 2

  const eventEmitter = new EventEmitter();
  const onEventA = expect(eventEmitter).to.emit('eventA');

  await onEventA;                 // Promise will be NEVER resolved
  // Test fails only because setTimeout throws an error and mocha handles it
});

Tech details

• where mocha adds process.on('uncaughtException', uncaught) :
  https://github.com/mochajs/mocha/blob/master/lib/runner.js#L871

Possible solution
Use try-catch for setTimeout() and on() handlers:

try {
    assert(...);
    resolve(args);
} catch (err) {
    reject(err);
}