- The NixOS VM test framework, `pkgs.nixosTest`/`make-test-python.nix`, now requires detaching commands such as `succeed("foo &")` and `succeed("foo | xclip -i")` to close stdout.
- The NixOS VM test framework, `pkgs.nixosTest`/`make-test-python.nix` (`pkgs.testers.nixosTest` since 22.05), now requires detaching commands such as `succeed("foo &")` and `succeed("foo | xclip -i")` to close stdout.
This can be done with a redirect such as `succeed("foo >&2 &")`. This breaking change was necessitated by a race condition causing tests to fail or hang.
It applies to all methods that invoke commands on the nodes, including `execute`, `succeed`, `fail`, `wait_until_succeeds`, `wait_until_fails`.