Characterization Tests (Golden Master / Feathers)

Create characterization tests for an existing subsystem whose behavior is unclear, messy, or AI-generated. Pin down current observable behavior so that refactoring and incremental replacement are safe.

Input

Subsystem / entrypoint / behavior surface to lock down: $ARGUMENTS

Preconditions:

• At least one runnable entry point (function, CLI command, server route, etc.)
• A concept capsule is NOT required, but use its vocabulary if one exists

Procedure

1. Identify the behavior surface

List 1-3 surfaces to lock down: public functions, CLI commands, HTTP endpoints, file-in→file-out, serialized outputs. Prefer the most stable public surface available.

2. Minimal fixture set