Service as Consumer and Provider

This example demonstrates a common microservice pattern where one service plays both roles in contract testing:

• Provider to a frontend client (frontend-web → user-service)
• Consumer of an upstream auth service (user-service → auth-service)

Overview

• Frontend Client: Consumer-facing client used by frontend-web
• Auth Client: Upstream client used by user-service to call auth-service
• User Service: FastAPI app under test (the service in the middle)
• Frontend Consumer Tests: Defines frontend-web's expectations of user-service
• Auth Consumer Tests: Defines user-service's expectations of auth-service
• Provider Verification: Verifies user-service against the frontend pact

Use the links above to view detailed documentation within each file.

What This Example Demonstrates

• One service owning two separate contracts in opposite directions
• Consumer tests for each dependency boundary
• Provider verification with state handlers that model upstream auth-service behaviour without needing it to run
• A Protocol-based seam that allows the real FastAPI application to run during verification while the upstream dependency is replaced in-process

Running the Example

uv run --group test pytest

Related Documentation

• Pact Documentation
• Provider States
• FastAPI Documentation
• pytest Documentation