Stub save Instance Method of Mongoose Model With Sinon

Question

I am trying to test a service function I use to save a widget using a Mongoose model. I want to stub out the save instance method on my model, but I cannot figure out a good

Answer 1

If were to test that, this is how I would approach it, first have a way to inject my mocked widget to the widget-service. I know there's node-hijack, mockery or something like node-di, they all have different styles, I'm sure there's more. Choose one and use it.

Once I get that right, then I create my widget-service with my mock widget module. Then I do something like this(this is using mocha btw):

// Either do this:
saveStub = sinon.stub();
function WidgetMock(data) {
    // some mocking stuff
    // ...
    // Now add my mocked stub.
    this.save = saveStub;
}


// or do this:
WidgetMock = require('./mocked-widget');
var saveStub = sinon.stub(WidgetMock.prototype, 'save');


diInject('widget', WidgetMock); // This function doesn't really exists, but it should
// inject your mocked module instead of real one.

beforeEach(function () {
    saveStub.reset(); // we do this, so everytime, when we can set the stub only for
    // that test, and wouldn't clash with other tests. Don't do it, if you want to set
    // the stub only one time for all.
});
after(function () {
    saveStub.restore();// Generally you don't need this, but I've seen at times, mocked
    // objects clashing with other mocked objects. Make sure you do it when your mock
    // object maybe mocked somewhere other than this test case.
});
it('createWidget()', function (done) {
    saveStub.yields(null, { someProperty : true }); // Tell your stub to do what you want it to do.
    createWidget({}, function (err, result) {
        assert(!err);
        assert(result.someProperty);
        sinon.assert.called(saveStub); // Maybe do something more complicated. You can
        // also use sinon.mock instead of stubs if you wanna assert it.
        done();
    });
});
it('createWidget(badInput)', function (done) {
    saveStub.yields(new Error('shhoo'));
    createWidget({}, function (err, result) {
        assert(err);
        done();
    });
});

This is just a sample, my tests sometimes get more complicated. It happens that most of the time, the backend calling function(here it is, widget.save) that I want to mock, is the one that I want it's behavior to change with every different test, so that's why I reset the stub everytime.

Here's also another example for doing similar thing: https://github.com/mozilla-b2g/gaia/blob/16b7f7c8d313917517ec834dbda05db117ec141c/apps/sms/test/unit/thread_ui_test.js#L1614