test.spec.js

/// <reference types="Cypress" />

context('Actions', () => {

    it('should fill out creditcard', () => {
        cy.getWithinIframe('[name="cardnumber"]').type('4242424242424242');
        cy.getWithinIframe('[name="exp-date"]').type('1232');
        cy.getWithinIframe('[name="cvc"]').type('987');
        cy.getWithinIframe('[name="postal"]').type('12345');

        // adjust this to use your own pay now button
        cy.get('[data-cy="pay-now"]').click();
    });
});