To run all tests you will need to run the kennethreitz/httpbin and ghcr.io/chatterino/twitch-pubsub-server-test:latest docker images.

For example:

docker run --network=host --detach ghcr.io/chatterino/twitch-pubsub-server-test:latest
docker run -p 9051:80 --detach kennethreitz/httpbin

If you're unable to use docker, you can use httpbox (httpbox --port 9051) and Chatterino/twitch-pubsub-server-test manually.