Dependencies for the test environment

When I updated to Elixir 0.12.3, I found the dependency behaviour changed for the test environment. Running

Copymix deps.get

Gets dependencies for production(?), so I'm able to compile with

Copymix

However

Copymix test

Fails with Unchecked dependencies for environment test:.

Get test dependencies with

CopyMIX_ENV=test mix deps.get