Getting 404 when running integration tests in Chrome (Selenium).

I am writing some integration and unit tests for my SIWA package, and am using Facebook's ChromeDriver (headless) to process the authorization request in the tests.

If I take the generated URL and paste it in Chrome, everything works. However, when I try to use the URL in my test, I get a 404 response.

Is there something that needs to be done differently for these kinds of tests?

Thanks for any advice you might have. 🙂