ci(tests): Also test macos-latest

Author: tony

.github/workflows/tests.yml

@@ -7,17 +7,25 @@ jobs:
     # Don't run twice for internal PRs from our own repo
     if: github.event_name == 'push' || github.event.pull_request.head.repo.full_name != github.repository
 
-    runs-on: ubuntu-latest
+    runs-on: ${{ matrix.os }}
     strategy:
       matrix:
         python-version: [ '3.10' ]
         tmux-version: [ '2.6', '2.7', '2.8', '3.0a', '3.1b', '3.2a', 'master' ]
+        os: [ ubuntu-latest ]
         # balance ci coverage across supported python/tmux versions with CI speed
         include:
           - python-version: '3.7'
             tmux-version: '2.6'
           - python-version: '3.7'
             tmux-version: 'master'
+          - python-version: '3.7'
+            tmux-version: '2.6'
+            os: macos-latest
+          - python-version: '3.7'
+            tmux-version: 'master'
+            os: macos-latest
+
     steps:
     - uses: actions/checkout@v1