Automated Routing QA: A Regression Testing Framework for Routing & Guidance Quality in Valhalla

Valhalla currently lacks a scalable way to detect routing and guidance regressions introduced by pull requests. This project builds a three-component QA system: a coverage-driven Python route generator that produces 10,000+ test routes over a static Switzerland OSM extract, exercising all costing models and routing-relevant OSM tag categories; a GitHub Actions pipeline that builds Valhalla graphs from both master and PR code, runs all routes against both, and computes geometry and instruction diffs; and a React review application - built inside valhalla/web-app, where maintainers can inspect diffs route by route, compare map geometry and turn-by-turn instructions side by side, and accept or flag changes before the baseline updates. The deliverable is a maintainer-usable, publicly deployed QA tool that makes routing drift visible and catchable at PR review time.