promise-mock/src/index.js

Promise mock library for synchronous Promise testing

import Promise from 'promise-polyfill';

var root = typeof window === 'undefined' ? global : window;


function PromiseMock() {
  Promise.apply(this, arguments);
}
PromiseMock.prototype = Object.create(Promise.prototype);
Object.keys(Promise).forEach(function (key) {
  PromiseMock[key] = Promise[key];
});

// Queue of waiting callbacks
PromiseMock.waiting = [];


/**
 * Execute a pending Promise
 */
PromiseMock.run = function run(count) {
  var runTimes = count ? count : 1;

  if (PromiseMock.waiting.length === 0) {
    throw new Error('No Promises waiting. Can\'t Promise.run()')
  }

  while (runTimes > 0 && PromiseMock.waiting.length > 0) {
    PromiseMock.waiting.shift()();
    runTimes--;
  }
};

/**
 * Execute all pending Promises
 *
 * @param strict boolean Throw error if none waiting
 */
PromiseMock.runAll = function runAll(strict) {
  if (strict !== false && PromiseMock.waiting.length === 0) {
    throw new Error('No Promises waiting. Can\'t Promise.runAll()')
  }

  while (PromiseMock.waiting.length > 0) {
    PromiseMock.run();
  }
};


PromiseMock._orginal = null;
PromiseMock.install = function install() {
  PromiseMock._original = root.Promise;
  PromiseMock._originalImmediate = Promise._immediateFn;
  // Update the immediate function to push to queue
  Promise._immediateFn = function mockImmediateFn(fn) {
    PromiseMock.waiting.push(fn);
  };

  root.Promise = PromiseMock;
};

PromiseMock.uninstall = function uninstall() {
  PromiseMock.clear();
  if (PromiseMock._original) {
    root.Promise = PromiseMock._original;
  }

  if (PromiseMock._originalImmediate) {
    Promise._immediateFn = PromiseMock._originalImmediate;
  }
};

/**
 * Get the result of a Promise synchronously, throws on Promise reject
 * @param {Promise} promise
 * @returns {*}
 */
PromiseMock.getResult = function result(promise) {
  var result, error;
  promise.then(function (promResult) {
    result = promResult;
  }, function (promError) {
    error = promError;
  });
  PromiseMock.runAll();
  if (error) {
    throw error;
  }
  return result;
};

/**
 * Clear all pending Promises
 */
PromiseMock.clear = function clear() {
  PromiseMock.waiting = [];
};

export default PromiseMock;