Cypress: same tests that pass in browser fail in headless mode due to timeout

Question

When I run Cypress with vue-cli-service test:e2e --headless some tests inside a register request callback fail:

whereas normally when run in browser (vue-cli-service test:e2e) they pass:

 it('Submit WITHOUT promo code', () => {
        cy.server();
        cy.route({method: 'POST', url: 'api/register'}).as('register');

        cy.get('.thz-items-loading').should('not.be.visible');
        cy.get('#btn-submit').should('not.be.disabled');

        cy.get('iframe[name^="__privateStripeFrame"]').then(($iframe) => {
            const $body = $iframe.contents().find('body');

            cy.wrap($body).find('input:eq(1)').click({force: true}).clear();
            cy.wrap($body).find('input:eq(1)').type('4000000000009979'); // stolen card
            cy.get('#btn-submit').click(); // SUBMIT FORM

            cy.wait('@register').then(xhr => {
                cy.contains('#card-errors', 'Your card was declined.');
                // cy.get('.thz-items-loading').should('not.be.visible'); // FAILS
                // cy.get('.thz-items-loading').to.have.style('display', 'none'); // FAILS
                cy.get('#btn-submit').should('not.be.disabled'); // FAILS
                (...)
            });

            return null;
        });
(...)

Stack trace:

1) Trial registration form Submit WITHOUT promo code: CypressError: Timed out retrying: expected <button#btn-submit.thz-button.thz-radius-50.thz-btn-border-2.thz-align-center.thz-ff-g-hind-vadodara-600> not to be 'disabled' at Object.cypressErr (https://localhost:8000/__cypress/runner/cypress_runner.js:82944:11) at Object.throwErr (https://localhost:8000/__cypress/runner/cypress_runner.js:82909:18) at Object.throwErrByPath (https://localhost:8000/__cypress/runner/cypress_runner.js:82936:17) at retry (https://localhost:8000/__cypress/runner/cypress_runner.js:76454:16) at https://localhost:8000/__cypress/runner/cypress_runner.js:68529:18 at tryCatcher (https://localhost:8000/__cypress/runner/cypress_runner.js:131381:23) at Promise._settlePromiseFromHandler (https://localhost:8000/__cypress/runner/cypress_runner.js:129399:31) at Promise._settlePromise (https://localhost:8000/__cypress/runner/cypress_runner.js:129456:18) at Promise._settlePromise0 (https://localhost:8000/__cypress/runner/cypress_runner.js:129501:10) at Promise._settlePromises (https://localhost:8000/__cypress/runner/cypress_runner.js:129576:18) at Async._drainQueue (https://localhost:8000/__cypress/runner/cypress_runner.js:126305:16) at Async._drainQueues (https://localhost:8000/__cypress/runner/cypress_runner.js:126315:10) at Async.drainQueues (https://localhost:8000/__cypress/runner/cypress_runner.js:126189:14) at

Following lines inside cy.wait('@register') callback should pass in headless mode:

cy.get('.thz-items-loading').should('not.be.visible');
cy.get('.thz-items-loading').to.have.style('display', 'none');
cy.get('#btn-submit').should('not.be.disabled');

Looks like the timeout happens because elements #btn-submit and .thz-items-loading are not reachable in @register callback, even though in both cases they exist in DOM, but why? They are reachable before the request just fine.

I'm running Cypress 3.2.0 from a project created with vue-cli on Windows 10. Tested app is not a part of the project, is hosted elsewhere and is a static html page. Headless browser is Electron 59.

Answer 1

It turns out that Electron browser silently fails at executing newer syntax like Promises, that's why code in resolved Promise's then() callback which was supposed to change display property of .thz-items-loading and #btn-submit was never executed and tests expecting that change never passed.

Adding babel's polyfills before main.js of tested APP fixed this issue:

<script src="../../node_modules/@babel/polyfill/dist/polyfill.min.js"></script> <!-- or copy to root dir in build process -->
<script src="./main.js"></script>