Run backend regression tests in CI

.github/workflows/tests.yml

@@ -0,0 +1,38 @@
+name: Backend tests
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+concurrency:
+  group: backend-tests-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  tests:
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    strategy:
+      fail-fast: false
+      matrix:
+        python: ['3.11', '3.13']
+    steps:
+      - uses: actions/checkout@11d5960a326750d5838078e36cf38b85af677262 # v4
+        with:
+          persist-credentials: false
+      - uses: actions/setup-python@ece7cb06caefa5fff74198d8649806c4678c61a1 # v6
+        with:
+          python-version: ${{ matrix.python }}
+          cache: pip
+          cache-dependency-path: |
+            requirements.txt
+            requirements-test.txt
+      - name: Install test dependencies
+        run: python -m pip install -r requirements-test.txt
+      - name: Run offline regression suite
+        run: python -m pytest tests -q

README.md

@@ -302,3 +302,12 @@ surface and method documentation.
 ## License
 
 This project is released under the [MIT License](LICENSE).
+
+## Automated regression checks
+
+Install `requirements-test.txt` in a virtual environment, then run
+`python -m pytest tests -q` from the repository root. This runs the mocked
+regression suite without SPH credentials; the optional live timetable fixture
+test is skipped unless explicitly configured. GitHub Actions runs the suite on
+Python 3.11 and 3.13 for pull requests and pushes to main, caches pip downloads,
+and cancels superseded runs. This workflow does not deploy the backend.

requirements-test.txt

@@ -0,0 +1,3 @@
+-r requirements.txt
+pytest>=7.0.0
+httpx>=0.27.0