How to retest same URL using Mocha and Nock?

Question

Am using Mocha, Chai, Sinon, Proxyquire and Nock.

For this particular test scenario (for which this question is being asked), wish to test the exact same URL several times, each in a separate test that expects a different response.

For example, a response with no merchant feeds, 1 merchant feed, and yet again with 2 merchant feeds.

The existing code all works, furthermore if I run tests individually they pass.

However, if i run them together using Mocha in a single suite they fail. Believe the issue is that Nock hijacks the global http object for a given URL and each test (running asynchronously at the same time) is competing for the same global response reference.

In the scenario above, a response prepared with a canned reply of 1 merchant is getting say overwritten by the setup to respond with 2 merchants etc.

Is there a mechanism to avoid this happening, for instance guarantees around serial execution of async Mocha testcases (which I believed was the default behaviour).

Answer 1

Ok, so this works (sample code):

 beforeEach(function (done) {
            nock(apiUrl)
                .get('/dfm/api/v1/feeds?all=false')
                .reply(200, [
                    {'merchantId': 2, 'id': 2, 'disabled': false}
                ], { server: 'Apache-Coyote/1.1',
                    'set-cookie': [ 'JSESSIONID=513B77F04A3A3FCA7B0AE1E99B57F237; Path=/dfm/; HttpOnly' ],
                    'content-type': 'application/json;charset=UTF-8',
                    'transfer-encoding': 'chunked',
                    date: 'Thu, 03 Jul 2014 08:46:53 GMT' });

            batchProcess = proxyquire('./batchProcess', {
                './errorHandler': errorHandler.stub,
                './batchTask': batchTask.stub
            });

            winston.info('single valid feed beforeEach completed');
            done();
    });

There were lots of complicating factors. Two things to be aware of:

1). I had async testcases but was using beforeEach() without the done param. This was then causing the URL collisions. By explcitly declaring each beforeEach(done) and invoking done() Mocha will run in serial order and there is no longer an issue.

2). Be sure that if you have more than one test in same testsuite file, that any Nock fixtures you set in a previous test actually get executed IF you have declared the same URL in a subsequent test with alternate response. If the prior nock fixture doesn't get invoked then nock STILL retains the response from the wrong test (the previous one). This was my primary problem. You could argue that tests should not have any fixtures declared if they don't get run - but you could also argue this is still a bug in the way Nock works. The test fixtures were each isolated in their own describe / beforeEach(done) functions..

Update 2 days later... OK point 2). just bit me again, and I was pleased I wrote the note above to remind myself about this hard to debug issue. If you are using Mocha and Nock together be aware of this issue!!

Did eventually implement a nock helper function too, to assist with this (coffeescript here):

global.resetNock = ->
  global.nock.cleanAll()
  global.nock.disableNetConnect()

Then at the start of beforeEach just apply resetNock()

Answer 2

In response to your point 2), you can use nock.cleanAll() to cleanup all prepared nocks:

https://github.com/pgte/nock#cleanall

You can put this in an afterEach block to make sure you don't have leftover nocks between tests.

afterEach ->
  nock.cleanAll()