I'm also interested in this topic and I'm running into the same issues, login and redirects to accounts.shopify.com...
I'm wondering if there's a way to run automated tests with an embedded app?
I am also interested in this topic.
If anyone has a good way to test embedded apps using Cypress.io or any other tool I'll take it.
I tried using Capybara and Selenium but I did not find a way to install the app in the store automatically.