If you cannot or don't want to install docker locally, you can use docker machine do run the tests inside a VM or e.g. a Digital Ocean container. After having created a docker machine (lets say you called it default), just load its environment:

eval "$(docker-machine env default)"

Now you can run test/docker/run.sh as if docker was installed locally. Or maybe you just want to run a single test?

test/docker/run.sh --filter TaskTest::testTask

Or all tests that contain the word "parallel":

test/docker/run.sh --filter parallel

All parameters are directly passed to the phpunit command line tool as documented here.