q-flush

Defer and flush Q promise chains on demand, allows sync unit tests

Usually we cannot write sync unit tests if there are promises. For example, this code fails, because the console.log line executes before the .then callback executes.

var result;
Q(10).then(function (value) {
  result = value;
});
console.log(result); // prints undefined

Using q-flush you can collect all .then calls, and then execute them synchronously.

var Q = require('Q');
require('q-flush');

var result;
Q.deferFlush();
Q(10).then(function (value) {
  result = value;
});
Q.flush();
console.log(result); // prints 10

While this is possible, I still argue that a better option would be to pick a testing framework that understands the promises natively, for example Mocha. See Picking JavaScript testing framework.

Small print

Author: Gleb Bahmutov © 2015

• @bahmutov
• glebbahmutov.com
• blog

License: MIT - do anything with the code, but don't blame me if it does not work.

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Support: if you find any problems with this module, email / tweet / open issue on Github

MIT License

The MIT License (MIT)

Copyright (c) 2015 Gleb Bahmutov

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.