To run the tests across a selection of Ubuntu LTS versions:

docker build -t "python_magic/xenial:latest" -f test/Dockerfile_xenial .
docker build -t "python_magic/bionic:latest" -f test/Dockerfile_bionic .
docker build -t "python_magic/focal:latest" -f test/Dockerfile_focal .

docker run python_magic/xenial:latest
docker run python_magic/bionic:latest
docker run python_magic/focal:latest