How does one stub promise with sinon?
Solution 1
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})
Solution 2
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');
Solution 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
Solution 4
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'));
Solution 5
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!
epitka
You can see my LinkedIn profile at http://www.linkedin.com/in/edvardpitka
Updated on August 01, 2020Comments
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epitka almost 4 years
I have a data service with following function
function getInsureds(searchCriteria) { var deferred = $q.defer(); insuredsSearch.get(searchCriteria, function (insureds) { deferred.resolve(insureds); }, function (response) { deferred.reject(response); }); return deferred.promise; }
I want to test following function:
function search () { dataService .getInsureds(vm.searchCriteria) .then(function (response) { vm.searchCompleted = true; if (response.insureds.length > 100) { vm.searchResults = response.insureds.slice(0, 99); } else { vm.searchResults = response.insureds; } }); }
How would I stub the promise so that when I call getInsureds it would resolve the promise and return me the results immediately. I started like this (jasmine test), but I am stuck, as I don't know how to resolve the promise and pass in arguments needed.
it("search returns over 100 results searchResults should contain only 100 records ", function () { var results103 = new Array(); for (var i = 0; i < 103; i++) { results103.push(i); } var fakeSearchForm = { $valid: true }; var isSearchValidStub = sinon.stub(sut, "isSearchCriteriaValid").returns(true); var deferred = $q.defer(); var promise = deferred.promise; var dsStub = sinon.stub(inSearchDataSvc, "getInsureds").returns(promise); var resolveStub = sinon.stub(deferred, "resolve"); //how do i call resolve and pass in results103 sut.performSearch(fakeSearchForm); sinon.assert.calledOnce(isSearchValidStub); sinon.assert.calledOnce(dsStub); sinon.assert.called(resolveStub); expect(sut.searchResults.length).toBe(100); });