Sinon NodeJS stub only for module under test - node.js

Question

I have a module under test which uses https to PUT data to a response URL. Before doing so, it makes calls to the AWS SDK. I do not want to stub the calls that AWS SDK makes using https, but I do want to stub the call to https.post that my module under test uses (it's an AWS Lambda unit test if that matters).
Consider the following test code
describe('app', function () {
beforeEach(function () {
this.handler = require('../app').handler;
this.request = sinon.stub(https, 'request');
});
afterEach(function () {
https.request.restore();
});
describe('#handler()', function () {
it('should do something', function (done) {
var request = new PassThrough();
var write = sinon.spy(request, 'write');
this.request.returns(request);
var event = {...};
var context = {
done: function () {
assert(write.withArgs({...}).calledOnce);
done();
}
}
this.handler(event, context);
});
});
});
And my module under test (app.js)
var aws = require("aws-sdk");
var promise = require("promise");
exports.handler = function (event, context) {
var iam = new aws.IAM();
promise.denodeify(iam.getUser.bind(iam))().then(function (result) {
....
sendResponse(...);
}, function (err) {
...
});
};
// I only want to stub the use of https in THIS function, not the use of https by the AWS SDK itself
function sendResponse(event, context, responseStatus, responseData) {
var https = require("https");
var url = require("url");
var parsedUrl = url.parse(event.ResponseURL);
var options = {
...
};
var request = https.request(options, function (response) {
...
context.done();
});
request.on("error", function (error) {
...
context.done();
});
// write data to request body
request.write(...);
request.end();
}
How can I accomplish this?

Answer 1

You could use nock to mock specific HTTP/S requests, rather than function calls.
With nock, you can setup URL and request matchers that will allow requests through that don't match what you've defined.
Eg:
nock('https://www.something.com')
.post('/the-post-path-to-mock')
.reply(200, 'Mocked response!');
This would only intercept POST calls to https://www.something.com/the-post-path-to-mock, responding with a 200, and ignore other requests.
Nock also provides many options for mocking responses or accessing the original request data.