tests.nixpkgs-check-by-name: Fix non-reproducible test failures

        export NIX_STATE_DIR=$TEST_ROOT/var/nix

        export NIX_STORE_DIR=$TEST_ROOT/store

        # cargo tests run in parallel by default, which would then run into

        # https://github.com/NixOS/nix/issues/2706 unless the store is initialised first

        # Ensure that even if tests run in parallel, we don't get an error

        # We'd run into https://github.com/NixOS/nix/issues/2706 unless the store is initialised first

        nix-store --init

      '';

      # The tests use the shared environment variables,

      # so we cannot run them in parallel

      dontUseCargoParallelTests = true;

      postCheck = ''

        cargo fmt --check

        cargo clippy -- -D warnings