The Demo Is a Reducer: A Weekend Fixture Kit for Agent Side Projects

Description and use

A concise, reproducible demo command for testing agent prototypes using frozen time and tool fixtures.

Problem

Weekend agent prototypes often produce non‑deterministic demos that cannot be reliably reproduced, making review and validation difficult.

Outcome

The spike produces a deterministic, reproducible demo that can be verified by running demo.sh. It demonstrates how to isolate time, tool responses, and policy logic in code for reliable agent testing.

Workflow

• 1. Commit a frozen clock file files/CLOCK.txt with an ISO timestamp.
• 2. Create a fixture file fixtures/tools.json containing all tool responses the reducer may need.
• 3. Implement reduce.py to load the clock, read the incident JSON, look up tool results from the fixture, apply a deterministic severity table, and print a four‑line receipt.
• 4. Write demo.sh to run the reducer twice and compare stdout to fixtures/demo.stdout using diff.
• 5. Document skipped features in SKIPS.md to keep the spike focused.

Evidence

The demo is a command that reads frozen time, canned tool results, and one input file, then prints the same bytes on the second run.

Source

Five files are enough. More files usually mean the spike is leaking back in.

Source