Cypress: Stub open window

in my app there is an recommendations list, which on click opens a new window with a dynamic address:

$window.open(_shopURL, '_blank');

Now I'm trying to stub the windows.open event as shown in https://github.com/cypress-io/cypress-example-recipes/blob/master/examples/stubbing-spying__window/cypress/integration/window-stubbing.spec.js

Cypress.on('window:before:load', (win) => {
 win.open = cy.stub().as('windowOpen')
})


describe('Shop integration', () => {
 beforeEach(function () {
  cy.visitHome(countryCode, resellerId)
 })

it('can stub the window open event', function () {
  cy.get(`.recommendations-list .recommendations-cover:nth-of-type(1)`)
    .click()
  cy.get('@windowOpen').should('be.calledWith', 'page1.html')
})

But it's always opening the new tab and the logs are wrong: Cypress: stub open window

Does anybody has an idea why it's not working? Cheers!