Run unit tests on three operating systems (#285)

Co-authored-by: Ezio Melotti <ezio.melotti@gmail.com>

Author: hugovk

Diff for: .github/workflows/test.yml

@@ -41,13 +41,12 @@ jobs:
 
   unit:
     name: Unit tests
-    runs-on: ubuntu-latest
+    runs-on: ${{ matrix.os }}
     strategy:
       fail-fast: false
       matrix:
-        python-version:
-        - "3.13"
-        - "3.14"
+        python-version: ["3.13", "3.14"]
+        os: [windows-latest, macos-latest, ubuntu-latest]
 
     steps:
     - uses: actions/checkout@v4
@@ -69,5 +68,6 @@ jobs:
     - name: Upload coverage
       uses: codecov/codecov-action@v5
       with:
+        flags: ${{ matrix.os }}
         name: Python ${{ matrix.python-version }}
         token: ${{ secrets.CODECOV_ORG_TOKEN }}