stripe async test woes

blah.js

      it('simplified test', async function() {
        expect.assertions(1);
        const stripe = Stripe(app.get('STRIPE_KEY'));
 
        const ntc = new NightlyTranChecker(app);
 
        jest
          .spyOn(stripe.transfers, 'create')
          .mockImplementation(() => ntc.stripe_cb(null, { whatever: 'blah' }));
 
        const { req, res } = setupParams();
        await ntc.checkTransactions(req, res);
 
        expect(stripe.transfers.create).toHaveBeenCalledTimes(1);
      });
 
 
 
// code under test
  async stripe_cb_inner(error, host, tour, tran, transfer) {
    console.log('stripe_cb_inner, error: ', error);
    console.log('stripe_cb_inner, transfer: ', transfer);
    if (error) {
      await this.emailFailureToAdmins(error, transfer);
      await this.emailFailureToHostAndAdmins(host, tour, tran);
    } else {
      await this.processStripeSuccess(host, tour, tran, transfer);
    }
  }
 
  async processTour(host, tour, tran) {
    console.log('processTour, tour: ' + tour);
    const stripe = Stripe(this.app.get('STRIPE_KEY'));
 
    let { stripe_user_id } = host;
    if (stripe_user_id) stripe_user_id = validator.escape(stripe_user_id);
 
    let { chargeId, currency, tourPrice } = tran;
    if (chargeId) chargeId = validator.escape(chargeId);
 
    this.stripe_cb = async (error, transfer) => {
      return await this.stripe_cb_inner(error, host, tour, tran, transfer);
    };
    this.stripe_cb = this.stripe_cb.bind(this);
 
    await stripe.transfers.create(
      {
        amount: tourPrice * 100,
        currency: currency,
        destination: stripe_user_id,
        source_transaction: chargeId
      },
      this.stripe_cb
    );
  }