Using Dockerfile as test environment

.github/workflows/tests.yml

@@ -1,22 +1,67 @@
 name: tests
 
-on: [push, pull_request]
+on:
+  push:
+    branches: [ "master" ]
+    # Publish semver tags as releases.
+    tags: [ 'v*.*.*' ]
+  pull_request:
+    branches: [ "master" ]
+
+env:
+  # Use docker.io for Docker Hub if empty
+  REGISTRY: ghcr.io
+  # github.repository as <account>/<repo>
+  IMAGE_NAME: ${{ github.repository }}
+  IMAGE_TAG: master
 
 jobs:
-  pytest:
+  build-and-test:
+
     runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+      # This is used to complete the identity challenge
+      # with sigstore/fulcio when running outside of PRs.
+      id-token: write
 
     steps:
-    - name: Checkout repository
-      uses: actions/checkout@v2
+      - name: Checkout repository
+        uses: actions/checkout@v3
+
+      # Set up BuildKit Docker container builder to be able to build
+      # multi-platform images and export cache
+      # https://github.com/docker/setup-buildx-action
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@f95db51fddba0c2d1ec667646a06c2ce06100226 # v3.0.0
+
+      # Login against a Docker registry except on PR
+      # https://github.com/docker/login-action
+      - name: Log into registry ${{ env.REGISTRY }}
+        if: github.event_name != 'pull_request'
+        uses: docker/login-action@343f7c4344506bcbf9b4de18042ae17996df046d # v3.0.0
+        with:
+          registry: ${{ env.REGISTRY }}
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
 
-    - name: Set up Python
-      uses: actions/setup-python@v2
-      with:
-        python-version: '3.11'
+      # Try pulling the Docker image first
+      - name: Pull Docker image
+        id: pull-image
+        run: |
+          set -e
+          if ! docker pull ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ env.IMAGE_TAG }}; then
+            echo "::set-output name=pull-failed::true"
+          fi
 
-    - name: Install dependencies
-      run: pip install -r tests/requirements.txt
+      # Build Docker image if pull fails
+      - name: Build Docker image if pull fails
+        if: steps.pull-image.outputs.pull-failed
+        run: |
+          docker build -t ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ env.IMAGE_TAG }} .
 
-    - name: Run pytest
-      run: pytest
+      # Run pytest tests within the Docker container
+      - name: Run pytest in Docker container
+        run: |
+          docker run ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ env.IMAGE_TAG }} pytest