Google provides emulators for Firestore and Pub/Sub, but nothing for Secret Manager. The only alternative I found was a basic testing helper with 18 commits and no production focus.
This is a production-grade implementation with:
100% API coverage (11/12 methods - IAM intentionally omitted since there's no auth in local testing)
Dual protocol support: native gRPC + REST/HTTP
Works with official GCP SDKs - just point at localhost instead of googleapis.com
Docker images for all variants
Within 2 months of quiet release, a company reached out saying they're using it in production CI/CD. I implemented their feature requests and added full REST API support.
Most useful for:
Hermetic testing (no network calls, deterministic) CI/CD without GCP credentials Local development without cloud costs
I used grpc-gateway to maintain semantic compatibility with GCP's official REST endpoints - same paths, same JSON format.
Happy to answer questions about implementation, use cases, or how it compares to other approaches.
GitHub: https://github.com/blackwell-systems/gcp-secret-manager-emul...