How does one stub promise with sinon?

Question

I have a data service with following function

function getInsureds(searchCriteria) {

    var deferred = $q.defer();

    insuredsSearch.get(searchCriteria,
         


        

Answer 1

At current sinon version v2.3.1, you can use stub.resolves(value) and stub.rejects(value) function

For example, you can stub myClass.myFunction with following code

sinon.stub(myClass, 'myFunction').resolves('the value you want to return');

or

sinon.stub(myClass, 'myFunction').rejects('the error information you want to return');

Answer 2

I had a similar situation and the accepted answer and comments were not working, but along with this question they helped me solve this in the following way. I hope it is helpful for somebody.

var Promise = require('bluebird');

var deferred = Promise.defer();
stub = sinon.stub(deferred, 'resolve').returns(deferred.promise);

deferred.resolve({data: data});
// or
deferred.reject(new Error('fake error'));

Answer 3

Also you can do something like this:

import sinon from 'sinon';

const sandbox = sinon.sandbox.create();

const promiseResolved = () => sandbox.stub().returns(Promise.resolve('resolved'));
const promiseRejected = () => sandbox.stub().returns(Promise.reject('rejected'));

const x = (promise) => {
  return promise()
    .then((result) => console.log('result', result))
    .catch((error) => console.log('error', error))
}

x(promiseResolved); // resolved
x(promiseRejected); // rejected

Answer 4

There's one more alternative I found. Much pain free than other methods.

You can use this npm package: sinon-stub-promise.

It abstracts much of the details, so that you don't have to invent the wheel again. Helped my write my tests after struggling to simulate a promise for long.

Hope it helps!

Answer 5

You just have to resolve the promise before you call the search function. This way your stub will return a resolved promise and then will be called immediately. So instead of

var resolveStub = sinon.stub(deferred, "resolve");

you will resolve the deferred with your fake response data

deferred.resolve({insureds: results103})