How to mock req.session on Mocha/Chai API Unit Test

Question

Using Mocha/Chai for REST API unit testing, I need to be able to mock req.session.someKey for a few of the end points. How can I go about mocking req.session?

I'm working on writing REST API unit tests for a NodeJS Express app that utilizes express-session. Some of these endpoints require the use of data stored in req.session.someKey, the endpoint is setup to return a 400 if req.session.someKey is undefined so I need to be able to mock it in order for the test to complete successfully.

Example code:

router.get('/api/fileSystems', utilities.apiAuth, (req, res) => {
  let customer = req.session.customer;
  let route = (customer === 'NONE') ? undefined : customer;

  if(route == undefined){
    res.status(400).send('Can't have customer of undefined');
  } else {
    let requestOptions = setRequestOptions(route);
    queryFileSystemInfo(requestOptions, (info) => {
      res.status(200).send(info);
    });

  }
});

What I've tried:

describe('/GET /api/fileSystems', () => {
  it('It should return information about the filesystem for a customer'), (done) => {
    chai.request(server)
      .get('api/fileSystems')
      .set('customer', '146')
      .end((err, res) => {
        res.should.have.status(200);
        done();
      });
  });
});

I attempted to use the .set() in order to set req.session but I believe that .set just sets the headers so I don't believe that I can update it that way unless I'm missing something.

Answer 1

For this project, I ended up having to set req.session.customer in our server.js file that has an app.use() call that uses a middleware function to set the current session. I was unable to actually find a package that directly mutates the req.session object at test time.