Assert arguments of stubbed methods with sinon - node.js

Question

import ManagerDaoStub from '../salesforce/__test__/ManagerDaoStub';
import criticalMerchants from '../criticalMerchants';
describe('criticalMerchants Unit Tests', () => {
before(() => {
ManagerDaoStub.initStubs();
});
after(() => {
ManagerDaoStub.restoreStubs();
});
it('assert the arguments of stubbed method', (done)=>{
let load = criticalMerchants.createCases(MERCHANT, DEVICE_ID, KEY, {});
return done();
});
})
This is the test file written in node criticalMerchants.test.js. The method i want to test which is createCases uses a method in ManagerDao, which has been stubbed in ManagerDaoStub as below.
import ManagerDao from '../ManagerDao';
class ManagerDaoStub {
constructor() {
this.sandbox = sinon.sandbox.create();
}
initStubs(sandbox) {
this.sandbox = sandbox || this.sandbox;
this.restoreStubs();
this.initFindOpenCases();
}
restoreStubs() {
this.sandbox.restore();
}
initFindOpenCases() {
let findOpenCases = this.sandbox.stub(ManagerDao, "findOpenCases");
findOpenCases
.withArgs(DEVICE_ID, KEY, match.func)
.callsArgWith(2, new Error("Test error"));
}
}
I want to assert whether this stubbed method initFindOpenCases was called with the right arguments (DEVICE_ID,KEY,null). I used
sinon.assert.calledWith(ManagerDaoStub.initFindOpenCases, DEVICE_ID, KEY, null) and this gives the following error:
AssertError: initFindOpenCases() is not stubbed.
Can someone suggest a proper way to do this?

Answer 1

First off, if ManagerDao.initFindOpenCases is an instance method (I'm unsure since you haven't shared its definition), then you can't stub it on the constructor like you've done here:
let findOpenCases = this.sandbox.stub(ManagerDao, "findOpenCases")
You need to either create an instance first-- then stub it on that instance-- or stub it on the prototype itself like so:
let findOpenCases = this.sandbox.stub(ManagerDao.prototype, "findOpenCases");
Secondly, you're making the same mistake again in your assertion, combined with another:
sinon.assert.calledWith(ManagerDaoStub.initFindOpenCases, DEVICE_ID, KEY, null)
ManagerDaoStub is the constructor, and it does not have an initFindOpenCases property. Its prototype does, and thus its instances do as well. On top of that, ManagerDaoStub.prototype.initFindOpenCases is still not a stub. It's a method you're calling to create a stub, but it is not itself a stub. More plainly, you're getting ManagerDao mixed up with ManagerDaoStub.
Assuming you make example change above, you can make your assertion work like this:
sinon.assert.calledWith(ManagerDao.prototype.initFindOpenCases, DEVICE_ID, KEY, null)
However, this isn't all I would recommend changing. This latter mixup is arising largely because you're vastly over-complicating the setup code of your test. You don't need to make an entire class to stub one method of ManagerDao.
Instead, just replace your before and after calls with these:
beforeEach(() => {
// Create the stub on the prototype.
sinon.stub(ManagerDao.prototype, 'findOpenCases')
.withArgs(DEVICE_ID, KEY, sinon.match.func)
.callsArgWith(2, newError('Test Error'));
});
afterEach(() => {
// As of sinon 5.0.0, the sinon object *is* a sandbox, so you can
// easily restore every fake you've made like so:
sinon.restore();
});
Aside from that, I recommend looking deeply into the difference between properties on a constructor and properties on its prototype. That knowledge will make stuff like this much easier for you. Best place to start is probably here on MDN.