Comment by pimterry

For the desperate people whose tests all just broke, I have a page on my public endpoint testing server that exactly reproduces the classic design: https://example.testserver.host/. You can just use update the URL and go back to blissful ignorance.

Also open-source and self-hostable: https://github.com/httptoolkit/testserver. Lots of other endpoints too, full docs here: https://testserver.host/