Give every xdist worker its own Xvfb (pytest-xvfb)

The first -n auto Tests run segfaulted in Tk's focus_force(): keyboard
focus is global to an X display, and four workers were sharing the one
xvfb-run display, stealing each other's focus. Stressed locally (layout +
keyboard tests x40, -n 8): 5 of 2760 failed on a shared display (focus-ring
assertions), 0 of 4600 with pytest-xvfb's per-process display -- and faster.
The geometry xvfb-run used moves into pyproject; the workflow keeps the
Xvfb install guard and drops xvfb-run.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0188kZdx3bb56QM8JFUnbHuM

.github/workflows/python-tests.yml

@@ -31,13 +31,15 @@ jobs:
       # The gate's keyboard and layout tests drive real Tk: widget heights and
       # the focus ring come from the font engine, and no mock can answer what
       # they ask. Without a display they do not skip -- they fail, which is how
-      # this job stayed red while the tests themselves were fine.
+      # this job stayed red while the tests themselves were fine. pytest-xvfb
+      # (requirements.txt, geometry in pyproject) starts one Xvfb per xdist
+      # worker: a shared display let workers steal each other's focus.
       # ubuntu-latest already ships xvfb, so the unconditional
       # `apt-get update && install` spent ~7 s to report "already the newest
       # version"; it now installs only on an image that lacks it.
       - name: Install a virtual X display
         run: |
-          command -v xvfb-run >/dev/null \
+          command -v Xvfb >/dev/null \
             || { sudo apt-get update && sudo apt-get install -y xvfb; }
 
       # -n auto spreads the suite over every runner core (pytest-xdist is in
@@ -46,7 +48,7 @@ jobs:
       # printed all ~1050 test ids.
       - name: Run tests with coverage
         run: |
-          xvfb-run -a -s "-screen 0 1600x1200x24" python -m pytest \
+          python -m pytest \
             -n auto \
             -p no:sugar \
             -q

app/pubspec.yaml

@@ -2,7 +2,7 @@ name: diet_guard_app
 description: "Companion phone app for diet_guard: log meals on the go."
 publish_to: 'none'
 
-version: 1.0.93+1
+version: 1.0.94+1
 
 environment:
   sdk: ^3.12.2

pyproject.toml

@@ -176,6 +176,14 @@ filterwarnings = [
     "ignore::DeprecationWarning",
     "default::pytest.PytestUnraisableExceptionWarning",
 ]
+# pytest-xvfb gives every pytest process -- each xdist worker included -- its
+# own Xvfb. Keyboard focus is global to an X display, so real-Tk tests from
+# several workers sharing one xvfb-run display stole each other's focus
+# (focus-ring assertions failed) and Tk segfaulted in focus_force(): 5 of 2760
+# stressed runs failed shared, 0 of 4600 with a display per worker.
+xvfb_width = "1600"
+xvfb_height = "1200"
+xvfb_colordepth = "24"
 
 [tool.coverage.run]
 source = ["diet_guard"]

requirements.txt

@@ -16,5 +16,6 @@ pytest-cov==7.1.0
 pytest-randomly==5.0.0
 pytest-sugar==1.1.1
 pytest-xdist==3.8.0
+pytest-xvfb==3.1.1
 requests==2.34.2
 ruff==0.16.9