mock-promise v0.1.4

mockPromise( )

A simple helper function that generates a timed mock promise. I thought it might be useful for people who want to play around with promises-- just npm install mock-promise or alternatively, paste the source into your code.

There are four optional arguments:

• resolveProbability - 0 - 1 The probability the promise will resolve. 0 rejects all, 1 resolves all.
• minTime / maxTime - Minimum/Maximum timeout in milliseconds the promise will resolve or reject.
• mockData - Custom data argument in case you want to generate a promise with data similar to what you expect.

mockPromise will always resolve within 1000ms when no arguments are passed in.

Source

var mockPromise = function(resolveProbability, minTime, maxTime, mockData) {
  if (resolveProbability === undefined || resolveProbability === null) {
    resolveProbability = 1;
  }

  if (minTime > maxTime) {
    console.error('minTime cannot be greater than maxTime');
  }

  // Creating mock data in case none is passed in
  var data = mockData || 'Resolved Value';

  // Picks a random time between minTime and maxTime
  var timeOut = Math.floor(Math.random()*((maxTime||1000)-(minTime||1)+1))+(minTime||1);

  // Creates a new promise. If the resolve probability is higher than
  // Math.random(), the promise will resolve. If not, it will be rejected.
  return new Promise(function(resolve, reject) {
    if (Math.random() < resolveProbability) {
      setTimeout(function() {
        var toBeResolved = { data: data, timeOut: timeOut + 'ms' };
        resolve(toBeResolved);
      }, timeOut);

    } else {
      setTimeout(function() {
        reject('Promise failed to resolve. ' + timeOut + 'ms');
      }, timeOut);
    }
  });
};

Example

Single promise

mockPromise(.3) // Notice this call will only generate mock promises that resolve 30% of the time
.then(function(result) {
  console.log(result);
})
.catch(function(error) {
  console.error(error);
});

/*
Usually returns something like this -> Promise failed to resolve. 586ms
Once in a while returns something like this -> { data: { body: 'Resolved Value' }, time: '644ms' }
*/

Promise.all

var promiseArray = [];
var myJSON = {hello: 'world'};

for(var i = 0; i < 10; i++) {
  promiseArray.push(mockPromise(1, 1000, 5000, myJSON));
}

Promise.all(promiseArray)
.then(function(promises) {
  console.log(promises);
})
.catch(function(error) {
  console.error(error);
});

/*
  ->  [ { data: { hello: 'world' }, time: '4054ms' },
        { data: { hello: 'world' }, time: '2894ms' },
        { data: { hello: 'world' }, time: '2859ms' },
        { data: { hello: 'world' }, time: '2594ms' },
        { data: { hello: 'world' }, time: '4797ms' },
        { data: { hello: 'world' }, time: '1181ms' },
        { data: { hello: 'world' }, time: '1061ms' },
        { data: { hello: 'world' }, time: '3013ms' },
        { data: { hello: 'world' }, time: '3158ms' },
        { data: { hello: 'world' }, time: '1651ms' } ]
*/