MockRequire

Simple module for mocking required dependencies. Works with any testing suite. (https://github.com/mateodelnorte/mockrequire).

Example Usage

Imagine your application uses the following module to onboard a user, in reaction to a recieved event. A service will require the module and call it, passing the event as a parameter. But, in the course of developing your application, you'd like to test the module in isolation from the rest of your code. The module depends on another module, 'my_db_lib'.

How can you test the module in isolation?

var db = require('my_db_lib');

module.exports = function onboardUser (event) {

  // we want to test this function's behavior, but need to isolate the behavior of the module apart from the behavior of it's dependency, the db. 

  db.User.findByEmail(event.email, function (err, user) {
    if(err) throw err;

    user.onboarding = 'complete';

    user.save(function (err) { 
      if(err) throw err; 
    });
  });
};

MockRequire provides a simple means of allowing you to mock dependencies of any module you require(). Want to unit test your code without ever having to hit a database, even though your code is require-ing your datastore modules directly? MockRequire is exactly what you need.

The following example uses 'mocha' and 'should' to create a unit test for the module above. We also use 'mockrequire' to mock out our dependencies, parts of our module we don't care to isolate in our test.

require('mocha'),
require('should');
var mockrequire = require('mockrequire');

var user = (function() {
  return {
    save: function (cb) {
      cb(null);
      this.saved = true;
    }
  };
})();

// instead of require()ing our handler directly, we can mockrequire() it and supply an object containing any child dependencies we would like to mock as well. Here we're mocking my_db_lib

var onboardUser = mockrequire('./handler', {
  'my_db_lib': {
    User: { 
      findByEmail: function (email, cb){
        cb(null, user);
      }
    }
  }
});

// we create our unit tests with mocha

describe('userPaymentComplete()', function(){
  onboardUser({ email: 'fake@email.com' });
  it('should set onboarding as \'complete\'', function() {
    user.should.have.property('onboarding').equal('complete');
  });
  it('should save user', function() {
    user.should.have.property('saved').equal(true);
  });
});