anchor.diff:  
           echo "Testing Nix installation..."
           # FIXME: should update ~/.bashrc.
  -        $ssh "source ~/.profile; nix-env --version"
  +        $ssh "source ~/.bash_profile || source ~/.bash_login || source ~/.profile || true; nix-env --version"
   
           echo "Done!"
           touch $out
  
positive.code:       system = "x86_64-linux";
      };
  
    };
  
    makeTest = imageName: testName:
  
negative.code:   ubuntu-14-04.install-default = makeTest "ubuntu-14-04" "install-default";
    #ubuntu-16-04.install-default = makeTest "ubuntu-16-04" "install-default";
    #ubuntu-22-10.install-default = makeTest "ubuntu-22-10" "install-default";
    fedora-36.install-default = makeTest "fedora-36" "install-default";
  }
  