ase test --nogui fails if $DISPLAY not set.

Checklist

• The issue remains in the development version of ASE.
• An minimal example is provided to reproduce the issue.

Summary

The ase test command normally tests the GUI too, but that can be annoying as it takes over your screen. It can be avoided in two ways.

• By unsetting $DISPLAY
• By specifying ase test --nogui

But doing both fails:

(venv-foss-2025b) 13:48 [surt] tmp$ unset DISPLAY
(venv-foss-2025b) 13:50 [surt] tmp$ ase test --nogui
usage: ase [-h] [--version] [-T] {help,info,test,gui,db,run,band-structure,build,dimensionality,eos,ulm,find,nebplot,convert,reciprocal,completion,diff,exec} ...
ase: error: KeyError: 'DISPLAY'
To get a full traceback, use: ase -T test ...