ci: add environments for different python versions

Test the project against each minor python version in GitHub Actions.

.github/workflows/tests.yml

@@ -25,9 +25,9 @@ jobs:
         uses: prefix-dev/[email protected]
         with:
           pixi-version: v0.25.0
-          environments: self
+          environments: default
       - name: Run Simple Tests
-        shell: pixi run -e self bash -e {0}
+        shell: pixi run -e default bash -e {0}
         run: |
           gridtk --help
           gridtk submit --help
@@ -38,38 +38,61 @@ jobs:
           gridtk delete --help
 
   tests:
+    strategy:
+      matrix:
+        pixi_environment: [test, test-py311, test-py310, test-py39]
     runs-on: ubuntu-22.04
-    permissions:
-      # Gives the action the necessary permissions for publishing new
-      # comments in pull requests.
-      pull-requests: write
-      # Gives the action the necessary permissions for pushing data to the
-      # python-coverage-comment-action branch, and for editing existing
-      # comments (to avoid publishing multiple comments in the same PR)
-      contents: write
     steps:
-      - uses: actions/checkout@v4
+      - name: Checkout repository
+        uses: actions/checkout@v4
         with:
           fetch-depth: 0
       - name: Setup Pixi
         uses: prefix-dev/[email protected]
         with:
           pixi-version: v0.25.0
-          environments: test
+          environments: ${{ matrix.pixi_environment }}
       - name: Run Tests
-        run: pixi run -e test test-ci
+        run: pixi run -e ${{ matrix.pixi_environment }} test-ci
+        env:
+          COVERAGE_FILE: ".coverage.${{ matrix.pixi_environment }}"
+      - name: Store coverage report
+        uses: actions/upload-artifact@v4
+        with:
+          name: coverage-${{ matrix.pixi_environment }}
+          path: .coverage.${{ matrix.pixi_environment }}
+
+  merge-coverage:
+    name: Merge the coverage reports from multiple coverages
+    needs: tests
+    runs-on: ubuntu-22.04
+    permissions:
+      # Gives the action the necessary permissions for publishing new
+      # comments in pull requests.
+      pull-requests: write
+      # Gives the action the necessary permissions for editing existing
+      # comments (to avoid publishing multiple comments in the same PR)
+      contents: write
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+      - name: Retrieve coverage artifacts
+        uses: actions/download-artifact@v4
+        id: download
+        with:
+          pattern: coverage-*
+          merge-multiple: true
       - name: Coverage comment
         id: coverage_comment
         uses: py-cov-action/python-coverage-comment-action@v3
         with:
           GITHUB_TOKEN: ${{ github.token }}
+          MERGE_COVERAGE_FILES: true
       - name: Store Pull Request comment to be posted
         uses: actions/upload-artifact@v4
         if: steps.coverage_comment.outputs.COMMENT_FILE_WRITTEN == 'true'
         with:
-          # If you use a different name, update COMMENT_ARTIFACT_NAME accordingly
           name: python-coverage-comment-action
-          # If you use a different name, update COMMENT_FILENAME accordingly
           path: python-coverage-comment-action.txt
 
   doc: