Configure CI tests and fix Docker Python version

Set `PYTHONPATH` in CI to ensure proper module discovery for tests. Add `PYTEST_ADDOPTS` for non-capturing output and fail-fast behavior.
Correct Dockerfile base image from `python:3.14-slim` to `python:3.12-slim`.

Author: timhauke

.github/workflows/test.yml

@@ -13,6 +13,9 @@ on:
 jobs:
   test:
     runs-on: ubuntu-latest
+    env:
+      PYTHONPATH: ${{ github.workspace }}
+      PYTEST_ADDOPTS: "--capture=no --maxfail=1"
     strategy:
       matrix:
         python-version: ["3.10", "3.11"]

Dockerfile

@@ -1,4 +1,4 @@
-FROM python:3.14-slim AS runtime
+FROM python:3.12-slim AS runtime
 
 ENV PYTHONUNBUFFERED=1 \
     PIP_NO_CACHE_DIR=1

tests/conftest.py

@@ -0,0 +1,9 @@
+"""Pytest configuration helpers."""
+
+import sys
+from pathlib import Path
+
+ROOT = Path(__file__).resolve().parents[1]
+
+if str(ROOT) not in sys.path:
+    sys.path.insert(0, str(ROOT))