Async call in beforeAll - jasmine

Question

Here are 2 samples of the same test. The only difference is that first one uses a promise in beforeAll block to assign a value to the variable while the second one assigns the value directly.
I raised a similar question Running spec after promise has been resolved with one of the comments pointing to this issue https://github.com/jasmine/jasmine/issues/412 which says that this is not supported in Jasmine. Has somebody figured out any workaround?
This fails with TypeError: Cannot read property 'forEach' of undefined
describe('Async car test', function () {
var cars;
beforeAll(function (done) {
// getCars() is a promise which resolves to ['audi', 'bmw']
getCars().then(function (data) {
cars = data;
console.log(cars) // ['audi', 'bmw']
done();
});
});
cars.forEach(function (car) {
it('car ' + car, function () {
expect(car).toBe(car);
});
});
});
This works fine
describe('Car test', function () {
var cars = ['audi', 'bmw'];
cars.forEach(function (car) {
it('car ' + car, function () {
expect(car).toBe(car);
});
});
});

Answer 1

Posting it as an answer, because I can't see things properly in comments.
I'm actually generating tests in my spec as well, and I'm using https://www.npmjs.com/package/jasmine-data-provider , I think you probably cannot generate it directly from resolved promise. And wrapping in another it doesn't work for you. This should work:
var using = require('jasmine-data-provider');
using(cars.forEach, function (car) {
it(car + ' should be' + car, function () {
expect(car).toBe(car);
});
});

Answer 2

This is not an issue with jasmine, it is an issue with your code.
beforeAll does not block subsequent code below the statement. it blocks code that is defined in it('should ...', (done)=>{...});
it('should have cars', (done) => {
cars.forEach(function (car) {
expect(car).toBe(car);
});
});

Answer 3

Since Jasmine does not support adding tests at runtime, the trick is to request the asynchronous data before starting Jasmine, and then using the retrieved data during runtime instead. This can be achieved with a singleton and programmatically starting Jasmine.
See here for a working example.
// car-collection.js
class CarCollection {
static load() {
return this.request()
then((data) => this.cars = data);
}
static request() {
// in practice this function would do something cooler
return Promise.resolve(['audi', 'bmw']);
}
}
modules.export = CarCollection;
Since CarCollection has methods that are static they will be shared across imports and this.cars will persist.
// launcher.js
const Jasmine = require('jasmine');
const CarCollection = require('./car-collection');
CarCollection.load()
.then(() => {
console.log(`car count is ${CarCollection.cars.length}`); // prints: car count is 2
const jasmine = new Jasmine();
jasmine.loadConfigFile(...); // path to jasmine.json
jasmine.execute();
});
An important step here is configure jasmine to know where to look for the test files. Either by loading a config or passing specifics into the execute function.
// car.spec.js
const CarCollection = require('./car-collection');
describe('test', function () {
CarCollection.cars.forEach((car) => {
it('test' + car, () => {
expect(car).toBe(car);
});
});
});
Now run node ./launcher.js and the tests should run.