#11664 Initial run on macOS on GHA.

.github/workflows/test.yaml

@@ -122,6 +122,18 @@ jobs:
           # Just Python 3.9 with default settings.
           - python-version: '3.9'
 
+          # Oldest macOS and olders Python supported versions.
+          # We pin a specific Python micro release due to a TK library bug.
+          # https://github.com/actions/setup-python/issues/402#issuecomment-1156015780
+          - python-version: '3.7.12'
+            runs-on: 'macos-10.15'
+            job-name: 'macos-10-default-tests'
+
+          # Newest macOS and newest Python supported versions.
+          - python-version: '3.10'
+            runs-on: 'macos-12'
+            job-name: 'macos-12-default-tests'
+
           # Windows, minimum Python version with select reactor.
           - python-version: '3.7'
             runs-on: 'windows-2022'
@@ -225,7 +237,7 @@ jobs:
     # If one of the above steps fails, fire up tmate for remote debugging.
     # This is fired for manual trigger or via the environment variable.
     - name: Tmate debug session
-      if: ${{ !cancelled() && (env.TMATE_DEBUG == 'yes' || github.event_name == 'workflow_dispatch' && inputs.debug_enabled ) }}
+      if: ${{ failure() && (env.TMATE_DEBUG == 'yes' || github.event_name == 'workflow_dispatch' && inputs.debug_enabled ) }}
       uses: mxschmitt/action-tmate@v3
       with:
         limit-access-to-actor: true