How to set up code coverage and unit tests for express functions?

I have a route defined like

app.post '/v1/media', authentication.hasValidApiKey, multipart, mediaController.create, mediaController.get

I want to write tests for the individual components of the route. So starting with authentication.hasValidApiKey, that's a function defined in another file:

exports.hasTokenOrApi = (req, res, next) ->
  if not req.headers.authorization
    return res.status(403).end()

  doOtherStuff...

In my test, I have:

authentication = require '../src/middlewares/authentication'

describe 'Authentication Middleware', ->
  before (done) ->
    done()

  it 'should check for authentication', (done) ->
    mock_req = null
    mock_res = null
    mock_next = null

    authentication.hasTokenOrApi mock_res, mock_req, mock_next
    done()

How do I deal with the req, res and next? And how can I setup code coverage to run? I am running my tests with: export NODE_ENV=test && ./node_modules/.bin/mocha --compilers coffee:'./node_modules/coffee-script/lib/coffee-script/register'