Maintainer of the tox here (note should be written always with lowercase t - just as pytest). tox by default takes full charge of the environment management via virtualenv, however note this doesn’t have to be the case. the tool is flexible enough to allow any environment management to be plugged in. For example this could be a simple shim instructing the OS to prepare an environment with following packages and then run this as a test. I’m currently in process of reorganizing the internals to make this even easier. Once done, we try out in practice, and if works good we can standardize it. Your current proposal misses tunes of nuances though to make it workable (like environment variables, working directory, test dependencies, test commands, parameterization of the commands, etc).