Rendering iFrame in Cypress

Can anyone help me render the iFrame for the following page in Cypress.

https://testnewpage.digitaldisbursements.org/

<iframe
  frameborder="0"
  title="Payment method selection section."
  src="https://staging-content.digitaldisbursements.com/latest/index.html"
  style="border: none; width: 100%; height: 355px; overflow: hidden"
></iframe>

It appears to me that no amount of waiting for the frame to load works for this page. The payment options never appear.

BUT, if you open the address in a new window the logos and payment buttons do appear.

This suggests you could try testing it in a new window - the approach is a little experimental but working.
See Unable to load a specific URL with Cypress for reference.

Here is a working test.

it('Should render the iframe', {timeout:20_000}, () => {
  cy.visit('http://testnewpage.digitaldisbursements.org/')

  cy.openWindow('http://testnewpage.digitaldisbursements.org/')

  const paymentMethods = [
    {imgSrc: 'virtual_mc3.png', caption: 'GET A PREPAID MASTERCARD'},    
    {imgSrc: 'paypal.png', caption: 'USE PAYPAL'},    
    {imgSrc: 'venmo.png', caption: 'USE VENMO'},    
    {imgSrc: 'zelle.png', caption: 'USE ZELLE'},    
    {imgSrc: 'virtual_mc3.png', caption: 'GET A PREPAID MASTERCARD'},   
  ]

  cy.get('iframe')
    .its('0.contentDocument')
    .find('body')
    .should('exist')
    .and('not.be.null')
    .within($body => {
      cy.get('#payment')
        .find('.MuiGrid-item')
        .each((paymentMethod, i) => {

          cy.wrap(paymentMethod)      // check the logo
            .find('button img')      // 1st button on card
            .should('have.attr', 'src')
            .and('contain', paymentMethods[i].imgSrc)

          cy.wrap(paymentMethod)     // check the button caption
            .find('button').eq(1)   // 2nd button on card
            .should('contain', paymentMethods[i].caption)
         })

    })
})

It uses the cy.openWindow() developed by Gleb Bahmutov here Cypress using child window with some adjustments.

Cypress.Commands.add('openWindow', (url, features) => {
  const w = Cypress.config('viewportWidth')
  const h = Cypress.config('viewportHeight')
  if (!features) {
    features = `width=${w}, height=${h}`
  }
  console.log('openWindow %s "%s"', url, features)

  return new Promise(resolve => {
    if (window.top.aut) {
      console.log('window exists already')
      window.top.aut.close()
    }
    // https://developer.mozilla.org/en-US/docs/Web/API/Window/open
    window.top.aut = window.top.open(url, 'aut', features)

    // letting page enough time to load and set "document.domain = localhost"
    // so we can access it
    setTimeout(() => {
      cy.state('document', window.top.aut.document)
      cy.state('window', window.top.aut)
      resolve()
    }, 10_000)
  })
})

Also, some setting needed in cypress.config.js

const { defineConfig } = require("cypress");

module.exports = defineConfig({
  e2e: {
    setupNodeEvents(on, config) {
    },
    chromeWebSecurity: false,
    modifyObstructiveCode: false,
  },
})