Jest Test Scheduler method

I have a simply class which runs a scheduler.

Something like this:

export class ExportScheduler {
    constructor(cron: string, private product: Product) {
        cron.schedule(cron, () => this.export());
    }

    async export(): Promise<any> {
        const access = new Accessor(this.product);

        return access.calc();
    }
}

And I would like to write a test using Jest, which basically tests the scheduler.

beforeEach(() => {
    clock = sinon.useFakeTimers();
    cut = new ExportScheduler(
       '* * * * *',
        product
    );
   });

it('should schedule exports', async () => {
    expect(await cut.export).not.toHaveBeenCalled();
    clock.tick(70000);
    expect(await cut.export).toHaveBeenCalledTimes(1);
}

But it tells me following:

Matcher error: received value must be a mock or spy function

How should I test this scheduler.