Mix use

gistfile1.js

// Liberally adapted from our test suites, which uses generators for complex steps (before/after/etc).
describe("With new customer", function() {
  let business;
  let customer1, customer2, customer3;

  before(function*() {
    // We have many tests, but you can only call listen() once
    // on an HTTP server, so this is a case for resolve-once, and
    // we use a promise.
    yield Server.listen();
  
    // This creates a new busines record in the database, with one
    // user, one product. It returns a generator function that has
    // multiple asynchronous steps, and return a model instance.
    business = yield Helper.newBusiness();
    
    // Let's add a customer. We're using an API that doesn't support
    // promises or thunks because real life use case.
    customer1 = new Customer({ business, name: "Assaf" });
    yield (resume)=> customer1.save(resume);
    
    // Now let's add two customers in parallel. The create method (new + save)
    // takes set of properties and a callback, let's thunk those.
    let create2 = Customer.create.bind(Customer, { business, name: "A" });
    let create3 = Customer.create.bind(Customer, { business, name: "A" });
    [customer2, customer3] = yield [one1, one2];
    
  });

  it("should .....")