Show HN: TwinStub – deterministic API simulation with signed webhook chains

Category: devtools

Tags: api-simulation, webhooks, state-machine, testing, mock-server, chaos-engineering

Score: 6.8/10 (Innovation: 6, Technical: 7, Documentation: 8, Utility: 6)

TwinStub is a deterministic API simulator that models stateful integration scenarios as YAML state machines with timed, HMAC-signed webhook chains. It targets teams building APIs where customers must handle rare edge cases like chargebacks, idempotency, and out-of-order events, compressing time and adding chaos tooling. The project is a single Go binary with a clear DSL, admin API, and CI-friendly validation.

Target audience: backend devs, QA engineers, API platform teams

Repository: https://github.com/twinstub/twinstub · Go · MIT

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