fastify-url-special-characters

Fastify test failures occur when special characters in route parameters are consumed or stripped before validation runs. Characters like # or ? break URL parsing, causing the router to miss the dynamic route and return a 404 instead of reaching your handler.

To test Fastify dynamic routes with special characters, replace problematic characters like # and ? with pass-through characters such as dots or spaces encoded in the URL. This ensures the request reaches the handler to trigger validation rather than failing at the routing level.

Routing failures happen when Fastify never matches the route due to URL parsing rules, returning a 404. Validation failures occur when the parameter reaches the handler but is rejected by format constraints, correctly returning a 400.

Safe URL characters for testing Fastify route parameters include pass-through characters like dots or spaces encoded in the URL. These comply with RFC 3986 parsing rules and safely reach the handler without being stripped or interpreted by the router.

Validate regex and length constraints for IDs by rewriting tests to use URL-encoded pass-through characters. This allows malformed IDs in dynamic routes like /gateways/:gatewayId/mcp to reach the handler, triggering the expected 400 validation failure.

Fastify supports RFC 3986 encoding rules for URL parsing, but characters like # and ? are consumed before reaching handlers. Testing dynamic routes requires using URL-encoded pass-through characters to ensure the request triggers validation instead of routing 404s.