开玩笑地测试没有适当功能的Lambda？ Node.js的

Question

Working with AWS Lambda to simply publish information, tests have been written(and are passing) for the branches of my code. However, I am unaware of how to test whether the return statement is called or not...

index.js

exports.handler = (event, context, callback) => {
  const headers = event.headers;

  if (! (headers && headers[filenameHeader])) {
    return callback(...);
  }

  if (!(event.body && event.body.length > 0)) {
    return callback(...);
  }

  return virtualService.publish(event, headers[filenameHeader], callback);
};

publish.service.js

exports.publish = (event, filename, callback) => {

  ...

  request(options).then(res => {
    console.log('Success response statusCode:' + res.statusCode);
    return callback(null, { "statusCode": 202 });
  }).catch(err => {
    console.log('Error thrown:' + err);
    return callback(null, { "statusCode": 500, "body": err });
  });
};

--- Tests --- I have managed to test the conditionals of the index.js file with things such as:

test('should return a 400 due to the X-File-Name header not being present', function (done) {
    lambda.handler(event, null, (err, request) => {
      should.not.exist(err);
      should.exist(request);
      expect(request.statusCode).toBe(400);
      expect(console.log).toHaveBeenCalledWith('X-File-Name Header not supplied');
      done();
    });
  });

However I am looking to test the line: return virtualService.publish(event, headers[filenameHeader], callback); ...

I have written something I know to be wrong, but I am hoping that it is somewhat in the right direction...

test('test the return function is called within index.js', function(done) {
    lambda.handler(event, null, (err, request) => {
      expect(publish).toHaveBeenCalled();
    })
  })

Answer 1

I did not test it, but I think stubbing virtualService.publish with sinon would work :

//import * is important here as it will allow you (and sinon) to get the method reference and stub it
import * as virtualService from './lib/service/publish.service'; 

test('test the return function is called within index.js', () => {
    const stubbedPublish = sinon.stub(virtualService, 'publish');
    //the callback  won't be called as we stubbed virtualService.publish, so I guess we can pass null
    lambda.handler(event, null, null)
    expect(stubbedPublish.callCount).toBe(1);
    virtualService.publish.restore();
}