Testing FastAPI API Authentication with Clerk JWT

Overview

This skill provides battle-tested guidance for testing FastAPI endpoints with Clerk JWT authentication based on real implementation lessons from Task 1.4 (Clerk Authentication Integration, 2025-11-11).

Verified Status: ✅ Production-ready (13/13 integration tests passing, end-to-end verified)

When to Use This Skill

• Testing FastAPI endpoints that require Clerk JWT authentication
• Validating JWT token verification logic (RS256 algorithm)
• Running end-to-end API tests with real Clerk tokens
• Troubleshooting authentication failures (401 errors)
• Verifying ALCOA+ audit logging with user attribution
• Debugging environment variable loading issues
• Testing with Clerk session tokens (not Client API tokens)

Prerequisites