How to test callback of function in Chai?

Question

I am using Slack API and I want to test does it work fine with response status code. Here is sending function :

    sendMsg(msg) {
      return this.slack.webhook({text: msg}, (err, res) => {
        if (err) {
            throw err;
        }
        console.log(res.statusCode) // = 200
        return res.statusCode;
      });
    }

And my test:

    it('Checks connection with Slack', (() => {
      let slack = new Slack();
      let res = slack.sendMsg('test');
      expect(res).to.equal(200);
    }));

But ofc. it's giving me request object to slack. I want to wait for response object from slack API. Thanks in advance.

Answer 1

It looks like slack.webhook takes in a callback, which is how you retrieve the status. The problem is that the caller of sendMsg has no way of getting that status.

One way to solve this is to have sendMsg take in a callback:

sendMsg(msg, onStatusReceived) {
  this.slack.webhook({text: msg}, (err, res) => {
    if (err) {
        throw err;
    }
    console.log(res.statusCode) // = 200
    onStatusReceived(res.statusCode);
  });
}

Then in your test, use done to end the test when the callback is invoked:

it('Checks connection with Slack', (done) => {
  let slack = new Slack();
  slack.sendMsg('message', status => {
    expect(status).to.equal(200);
    done();
  });
});

Another way is to have sendMsg wrap slack.webhook in a promise, so the caller can do sendMsg().then(...).