mixin-test.js

import Ember from 'ember';
import StartExamMixin from '../../../mixins/start-exam';
import { module, test } from 'qunit';
import sinon from 'sinon';

const {
  RSVP,
  ActionHandler
} = Ember;

module('Unit | Mixin | start exam');

test('action start', function(assert) {
  assert.expect(3);

  let spy, resolve;

  const exam = {
    createExamSession() {
      return new RSVP.Promise((res) => { resolve = res; });
    }
  };

  const StartExamObject = Ember.Object.extend(ActionHandler, StartExamMixin, {
    attrs: {
      actionTransitionToSession: spy = sinon.spy()
    }
  });

  const subject = StartExamObject.create();
  const done    = assert.async();

  const promiseWaiter = (prm) => {
    prm.then(() => {
      assert.ok(spy.calledOnce);
      assert.ok(spy.calledWith('foo'));
      done();
    });
  };

  subject.send('start', exam, promiseWaiter);
  assert.ok(spy.notCalled);
  resolve({id: 'foo'});
});

mixin.js

import Ember from 'ember';
import _     from 'npm:lodash';

export default Ember.Mixin.create({
  actions: {
    start(exam, promiseWaiter) {
      const prm =
        exam
          .createExamSession()
          .then((session) => {
            this.attrs.actionTransitionToSession(session.id);
          });

      if (_.isFunction(promiseWaiter)) {
        promiseWaiter(prm);
      }
    }
  }
});