Investigations

API Recorder

Go October 2025

An HTTP API recorder and playback tool in Go enabling offline development and AI-assisted API migration testing.

Proxyy records HTTP request/response pairs and replays them offline. The primary use case is enabling AI-assisted migration of services — record the old API's behaviour, then use the recordings to verify the new implementation matches exactly.

In record mode, it proxies requests to real APIs while saving request/response pairs as JSON with SHA256-based matching (method + URL + headers + body). In playback mode, it serves recorded responses without any network access needed.

The admin API (port 8081) lets you switch modes and manage recordings. Integration requires zero code changes — just configure URL prefixes to route through the proxy on port 8080.

The repo includes a full migration test system with CRM v1 (Node), CRM v2 (Go), CRM v3, external service mocks, and a test suite. BDD feature tests in Gherkin format and TDD unit tests with testify provide comprehensive coverage.

What this project demonstrates

Record/playback HTTP API interactions
SHA256-based request matching
Zero-code-change integration via URL prefix routing
Full migration test system: CRM v1/v2/v3
BDD Gherkin tests + TDD unit tests with testify
Enables AI-assisted API migration verification

Technologies

GoProxyAPI TestingBDDMigration

© 2026 Jonathan Leahy · v1.0.9