Unit Test for the New Stripe Checkout - ruby

Question

This isn't much of a code since I'm really new to testing. I've done a couple of unit test using capybara and rspec but all of them were on my existing app. For Stripe how ever, once you click the checkout button you are redirected to their own checkout page, from there I lost any way to control or access any of the page.
Basic test code is as follows:
it "visits stripe checkout" do
login_as(user)
visit my_page
click_button "Checkout"
sleep(2) // im adding sleep to delay it since there's a bit of loading once checkout is clicked
// From here I cant access anything anymore such as
expect(page).to have_selector(".ProductSummary-totalAmount", text: "$20.00")
//Note: This is just for me to confirm Im in the page and that is the actual class name on the checkout app
end
Would appreciate if someone can help or point me to the right direction. Much better if anyone can show me an example on how to fill in the credentials once on the checkout page. Links also helps.
P.S. I did my research but most discussions were using the old checkout on stripe which is just an iframe/modal.

Answer 1

General rule of testing is that you should test your own code, not other's. Testing Stripe Checkout adds unnecessary complexity to your tests and is brittle, what if Stripe changes something on their Checkout page that breaks your tests?
Instead you should just test that your button can be clicked and mock the possible responses from stripe.redirectToCheckout. You also test that the success and cancel URL you set when creating the Checkout Session renders and works as expected.