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Question

In unit testing Loopback it is necessary to use callbacks with the upsert methods. So for example ... instead of writing something along the lines of this:

before(function () {

    Student = server.models.Student
    Course = server.models.Course


    Course.upsert({id: 1, key: 'A', department: 'Original department'})
    Student.upsert({id: 1, points: 5000})


})

it is necessary to ensure that callbacks are used with the upsert. Since I have a lot of models I am initializing below I use async:

before(function (done) {

    Student = server.models.Student
    Course = server.models.Course


    async.waterfall([
            function (callback) {
                Course.upsert({id: 1, key: 'A', department: 'Original department'}, callback)
            },
            function (f, callback) {
                Student.upsert({id: 1, points: 5000}, callback)
            },

        ],
        function (err, results) {
            done(err)
        })

})

Instead of async, how would the code above be changed to use Promises?

My thought is that with promises, I would be able to write some code that looks like this:

before(function (done) {

    Student = server.models.Student
    Course = server.models.Course


    Course.upsert({id: 1, key: 'A', department: 'Original department'})
      .then(Student.upsert({id: 1, points: 5000})
      .then(function(err) { done(err) } 


})

but I have been unsuccessful tying into promises.

EDIT from answers below ...

 before(function (done) {


    Course = server.models.Course

    Course.upsertWithPromise = Promise.promisify(Course.upsert)

    Course.upsertWithPromise({id: 1, key: 'A', department: 'Original department'})
        .then(done)

  } 




it.only('Course upsert', function (done) {

    Course.findById(1, function (err, course) {

        expect(course.id).to.equal(1)
        expect(course.department).to.equal('Original department')

        done()


    })
})

Answer 1

There are two possible solutions. First is manual promisification. Your functions will look like this:

server.models.Student.upsert = function(data) {  // Note NO CALLBACK
  return new Promise(function(resolve, reject) {
    // Here can do all async staff and when done sucessfully call:
    resolve(result);
    // OR on error call:
    reject(err);
  });
}

Second solution will be use library for the same purpose.

1. var q = require('q'); // Use q library
2. DO NOT modify your models. They must take callback as last argument (follow node convention)
3. var server.models.Student.upsertWithPromice = q.denodeify(server.models.Student.upsert);
4. profit.

Then your code from your example should work fine.