Finer test, checking the store

billing.spec.js

it("populates the store with server data", (done) => {
    const invoice = {
        reference: '0001',
        amount: '10.00',
    };
    store.subscribe(() => {
        expect(store.getState().billing.invoices[0]).toEqual(invoice);
        done();
    });
    stubApi.getInvoices = () =>{
        return Promise.resolve([invoice]);
    };

    createPage();
});