Difference between supertest's expect and then?

问题

When using supertest for testing async HTTP requests in JavaScript, what's the difference between these two snippets? Is one of them correct and the other one wrong?

request('http://localhost:8080/').get('/api/people') .expect(res => res.body.should.have.length(5))

vs.

request('http://localhost:8080/').get('/api/people') .then(res => res.body.should.have.length(5))

The only differences I could notice were:

• expect returns a Test object and, when test fails, prints a large stack trace
• then returns a Promise object and, when test fails, prints a small stack trace

回答1:

Depending on what test runner you're using will obviously affect the answer, but something like Mocha will allow you to return the Promise directly in your test and this will wait to be resolved before the test passes.

So if you having something like:

describe('Your test case', function () {

  it('will wait for promise to resolve', function () {
    return request('http://localhost:8080/').get('/api/people')
      .then(res => res.body.should.have.length(5))
  })

})

Whereas in the other instance you really should use a done callback as per https://www.npmjs.com/package/supertest docs.

来源：https://stackoverflow.com/questions/50919242/difference-between-supertests-expect-and-then