Test on three operating systems

Author: hugovk

.github/workflows/test.yml

@@ -41,13 +41,14 @@ jobs:
 
   unit:
     name: Unit tests
-    runs-on: ubuntu-latest
+    runs-on: ${{ matrix.os }}
     strategy:
       fail-fast: false
       matrix:
         python-version:
         - "3.13"
         - "3.14"
+        os: [windows-latest, macos-latest, ubuntu-latest]
 
     steps:
     - uses: actions/checkout@v4
@@ -69,5 +70,6 @@ jobs:
     - name: Upload coverage
       uses: codecov/codecov-action@v5
       with:
+        flags: ${{ matrix.os }}
         name: Python ${{ matrix.python-version }}
         token: ${{ secrets.CODECOV_ORG_TOKEN }}