Also here: https://stackoverflow.com/questions/42982267/tox-set-default-values-for-missing-environment-variables

I've found that I would really like to use environment variables to control flow - especially when testing. But I also would like to set a default behavior based on whether or not an environment variable is present. In bash, I'd just use: ${ENV_VAR:-default_value}, but I don't have that basic option in Tox (unless I missed it).

Is there a way?