httpbin is an amazing web service for testing HTTP libraries. It
has several great endpoints that can test pretty much everything
you need in a HTTP library. The only problem is: maybe you don't
want to wait for your tests to travel across the Internet and back
to make assertions against a remote web service (speed), and maybe
you want to work offline (convenience).

Enter pytest-httpbin. Pytest-httpbin creates a pytest fixture that
is dependency-injected into your tests. It automatically starts up
a HTTP server in a separate thread running httpbin and provides
your test with the URL in the fixture.

Homepage:
https://github.com/kevin1024/pytest-httpbin
