测试expressJS的基本中间件

Question

There is a very basic middleware, which I would like to test.

First question is what kind of test I'm using. For my understanding, I cannot write a unit test for this code. I would call that an integration test. Is that correct?

The second problem ist the test itself: I'm running into a timeout, althoug I've used done() . What am I doing wrong? And is that the correct way to test this middleware?

/middlewares/graphql.js

module.exports = (req, res, next) => {
  res.header('Access-Control-Allow-Origin', '*')
  res.header('Access-Control-Allow-Headers', 'Content-Type, Authorization, Content-Length, X-Requested-With')
  if (req.is('application/graphql')) {
    req.body = { query: req.body }
  }
  if (req.method === 'OPTIONS') {
    res.sendStatus(200)
  } else {
    next()
  }
}

/tests/middlewares/graphql.js

import nodeMocks from 'node-mocks-http'
import middleware from '../middlewares/graphql'

describe('GraphQL middleware', () => {
  it('Should return 200 for valid Content-Type header', (done) => {
    const req = nodeMocks.createRequest({
      headers: {
        'Content-Type': 'application/graphql'
      },
      body: {
        content: 'anything'
      },
      method: 'OPTIONS'
    })
    const res = nodeMocks.createResponse()
    middleware(req, res, (err) => {
      expect(res.statusCode).toEqual(200)
      expect(res.body.content).toEqual('anything')
      expect(err).toBeNull()
      done()
    })
  })
})

Answer 1

middleware is a function with (req, res, next) as parameters. You send req , res and a callback where you handle the assertions. Ie the assertion testing is passed in as next() .

But there is no reason for next() to be called when you pass in OPTIONS as request method. The middleware will then do res.sendStatus(200) instead. So you have to call middleware as an ordinary function instead (for this particular test).

middleware(req, res);

expect(res.statusCode).to.equal(200);
expect(res.body.content).to.equal('anything');
done();

It will fail on the except for res.body , but that's because the middleware function is written that way.

As long as you only test the middleware function I would call it unit testing. If you care about what happens after next() gets called I would call it integration testing. But what it's called is not that important as long as it's tested.

You can see this answer for testing when the middleware has to call next() .