2014-02-mocha-test-harmony-generators.md

title	date	author	layout	npm	github
Enabling Generators in Mocha	2014-02-03 12:30	Blake Embrey	article	co-mocha	blakeembrey/co-mocha

Update: It's on npm. Just npm install co-mocha and --require co-mocha in your mocha script to test using generators.

For the last week, I've been working on a new project that uses node 0.11 and generators. Aside from the numerous benefits with generators in the application, I also integrated generators into my test suite. By using mocha and co, you can also enable support for generator functions in your test suite.

var co = require("co");
var mocha = require("mocha");
var Runnable = mocha.Runnable;
var run = Runnable.prototype.run;

/**
 * Override the Mocha function runner and enable generator support with co.
 *
 * @param {Function} fn
 */
Runnable.prototype.run = function (fn) {
  if (this.fn.constructor.name === "GeneratorFunction") {
    this.fn = co(this.fn);
    this.sync = !(this.async = true);
  }

  return run.call(this, fn);
};

Save the snippet of code above into a JavaScript file and pass the filename to mocha.opts.

mocha --harmony-generators --require test/support/co-mocha

Writing tests using generators has made testing even more enjoyable, so I decided to release the code on Github with some accompanying tests and test coverage.