CI debugging, a fix?

.github/workflows/ci.yml

@@ -32,8 +32,8 @@ jobs:
         uses: mxschmitt/action-tmate@v3
         with:
           detached: true
-          timeout-minutes: 20
           limit-access-to-actor: true
+        timeout-minutes: 20
 
       - name: Install system dependencies
         shell: bash
@@ -90,16 +90,13 @@ jobs:
         working-directory: PyOP2
         run: make lint
 
-      - name: Check MPI
-        shell: bash
-        working-directory: PyOP2
-        run: mpiexec -n 4 python3 -c "from mpi4py import MPI; print(MPI.COMM_WORLD.rank, MPI.COMM_WORLD.size)"
-        timeout-minutes: 10
-
       - name: Run tests
         shell: bash
         working-directory: PyOP2
-        run: pytest --tb=native --timeout=480 --timeout-method=thread -o faulthandler_timeout=540 -v test
+        run: |
+          # Running parallel test cases separately works around a bug in pytest-mpi
+          pytest -k "not parallel" --tb=native --timeout=480 --timeout-method=thread -o faulthandler_timeout=540 -v test
+          mpiexec -n 3 pytest -k "parallel[3]" --tb=native --timeout=480 --timeout-method=thread -o faulthandler_timeout=540 -v test
         timeout-minutes: 10
 
       - name: Build documentation