CI: Run tests in parallel with pytest-xdist

Pass the options at each call site rather than putting them in addopts, so pytests may also run without test-xdist.

REVERSE dropped because xdist runs tests in arbitrary order anyhow. That matrix entry still does PYTHONOPTIMIZE=1.

Co-authored-by: Hugo van Kemenade <1324225+hugovk@users.noreply.github.com>

Author: akx

.ci/test.cmd

@@ -1,3 +1,5 @@
 python.exe -c "from PIL import Image"
 IF ERRORLEVEL 1 EXIT /B
-python.exe -bb -m pytest -vv -x -W always --cov PIL --cov Tests --cov-report term --cov-report xml Tests
+python.exe -bb -m pytest -vv -x -W always Tests -m "isolated"
+IF ERRORLEVEL 1 EXIT /B
+python.exe -bb -m pytest -vv -x -W always Tests -m "not isolated" --numprocesses=logical --dist=worksteal --cov PIL --cov Tests --cov-report term --cov-report xml

.ci/test.sh

@@ -4,4 +4,7 @@ set -e
 
 python3 -c "from PIL import Image"
 
-python3 -bb -m pytest -vv -x -W always --cov PIL --cov Tests --cov-report term --cov-report xml Tests $REVERSE
+python3 -bb -m pytest -vv -x -W always Tests -m "isolated"
+python3 -bb -m pytest -vv -x -W always Tests -m "not isolated" \
+  --numprocesses=logical --dist=worksteal \
+  --cov PIL --cov Tests --cov-report term --cov-report xml

.github/workflows/test.yml

@@ -46,7 +46,7 @@ jobs:
           "3.11",
         ]
         include:
-        - { python-version: "3.13", PYTHONOPTIMIZE: 1, REVERSE: "--reverse" }
+        - { python-version: "3.13", PYTHONOPTIMIZE: 1 }
         - { python-version: "3.12", PYTHONOPTIMIZE: 2 }
         # Intel
         - { os: "macos-26-intel", python-version: "3.11" }
@@ -125,9 +125,6 @@ jobs:
 
     - name: Test
       run: |
-        if [ $REVERSE ]; then
-          python3 -m pip install pytest-reverse
-        fi
         if [ "${{ matrix.os }}" = "ubuntu-latest" ]; then
           xvfb-run -s '-screen 0 1024x768x24' sway&
           export WAYLAND_DISPLAY=wayland-1
@@ -137,7 +134,6 @@ jobs:
         fi
       env:
         PYTHONOPTIMIZE: ${{ matrix.PYTHONOPTIMIZE }}
-        REVERSE: ${{ matrix.REVERSE }}
 
     - name: Prepare to upload errors
       if: failure()

Makefile

@@ -97,9 +97,9 @@ test:
 
 .PHONY: test-p
 test-p:
-	python3 -c "import xdist" > /dev/null 2>&1 || python3 -m pip install pytest-xdist
-	python3 -m pytest -qq -n auto
-
+	python3 -c "import xdist" > /dev/null 2>&1 || python3 -m pip install pytest-xdist psutil
+	python3 -m pytest -qq -m "isolated"
+	python3 -m pytest -qq -m "not isolated" --numprocesses=logical --dist=worksteal
 
 .PHONY: valgrind
 valgrind: