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Chapter 8: Do it to your own service

Your agent runs the whole loop from chapters 3 to 6 on a service it has not seen: record it, tune the replay and the mocks, and leave a regression test you can run before every change.

Time: about 5 minutes.

Prompt​

This prompt uses the mock-lab Go demo app as a stand-in for your service. To run it on your own service, replace mock-lab/languages/go with your service's directory.

Now treat mock-lab/languages/go as my own service. Use the quality-loop skill to record it, tune the replay and the mocks, and leave me a regression test I can run before every change.

What the agent does​

The quality-loop skill is the starting point for a service with no recording yet. It picks the other skills in order:

  • Runs the skill's environment check (quality-loop.sh doctor): proxymock version, existing recordings and blueprints, and free ports.
  • Reads the service to learn how it starts, what it calls and what it generates. This service has no database, calls the CNCF projects API (DOWNSTREAM_URL), and mints an access_token and an order_id on every run.
  • Writes a traffic script when the service has none. Here it wrote scripts/traffic.sh, which sends 14 requests covering every route, the token and order flow, and the 400, 401 and 404 error paths.
  • Records with proxymock record while the script runs, then replays behind proxymock mock and measures accuracy and the mock match rate.
  • Checks that the service's committed blueprint is needed by moving it aside for one run, then tunes a strict test config (go-service, from standard) with proxymock drift, one change per run.
  • Writes scripts/regression-test.sh and proves it: it passes on the current code, then fails with exit code 3 when the agent plants a one-word change, and the agent restores the code.

What you should see​

The tuning runs:

RunAccuracyMock matchAssertions passed (go-service)Change
Baseline100%100% (10/10)-Default scoring, committed blueprint loaded
Blueprint moved aside61.1%100%-Every auth and order call returned 401 on the stale recorded token. Blueprint restored
Strict config100%100%87.04%go-service created from standard
100%100%90.74%Body ignores ts, created
100%100%100% (54/54)Body also ignores order_id, access_token

The gate on a planted change (status changed from "created" to "placed"). Trimmed:

NEW MISMATCH: POST /api/orders status 201, body status created -> placed
NEW MISMATCH: GET /api/orders/order-dacf472b4b1ae3a8 status 200, body status created -> placed
...
 FAIL passAssertPct >= 100 - observed 92.59 (counts assertions, not requests: ...)
== regression gate exit 3 (verdict: proxymock/results/regress-2026-10-01_14-26-09/replay-verdict.json)

The skill's ### Result block. Trimmed:

### Result
- **Ran:** quality-loop "own service" flow on mock-lab/languages/go, all 4 steps: doctor (healthy), record (scripts/traffic.sh via :4143), replay tuning (5 runs + 1 ablation, test config go-service) and mock check, regression gate created and proven against a planted change
- **Outcome:** gate created — baseline PASS (exit 0); planted status change caught (exit 3, 4 NEW MISMATCH)
- **Numbers:** 18 inbound + 10 outbound pairs recorded; accuracy 100%, measured match 100% (10/10, 0 passthrough); go-service passAssertPct 87.04 → 100 (54/54)
- **Artifacts:** languages/go/proxymock/recorded-baseline/, proxymock/testconfigs/go-service.json, proxymock/results/regress-base/, proxymock/tuning/LOOP.md, scripts/traffic.sh, scripts/regression-test.sh (gate command: `scripts/regression-test.sh`)
- **Next:** proxymock-chaos-mock — "chaos-test /v1/inventory in mock-lab/languages/go with a 503 rule and check the retry loop survives"

Run scripts/regression-test.sh before each change. The first run creates the baseline, every later run is gated against it, and --rebase re-creates the baseline after an intended change. Exit code 0 is a pass, 1 is a failed check or a broken run, and 3 is a new mismatch against the baseline.

If it goes wrong​

  • Replayed calls fail with 401. The replay sends the stale token from the recording. The service needs a blueprint that carries the newly issued token into later requests, as the demo app's committed blueprint does. See Create and verify blueprints.
  • A replay with mismatches still exits 0. Without a test config and a baseline, a replay does not fail on mismatches. The generated script uses both.
  • Your teammates do not get the recording. Check .gitignore before you commit. mock-lab ignores proxymock/recorded-baseline/, so the agent listed the new files to commit and left the choice of a .gitignore exception to you.
  • The recording holds sensitive values. Check it before you commit it. In the demo the only sensitive-looking values were the app's own random demo tokens in 7 Authorization headers.

See Gate CI on replay results and CI/CD to run the gate in a pipeline.

Manual equivalent
cd mock-lab/languages/go

# Record while your traffic script runs against proxymock's inbound port 4143
proxymock record --out proxymock/recorded-baseline --app-port 8080 --app-health-endpoint / -- go run .
scripts/traffic.sh http://localhost:4143    # second terminal

# Replay with the dependencies mocked
proxymock mock --in proxymock/recorded-baseline --app-health-endpoint / -- go run .
proxymock replay --in proxymock/recorded-baseline --test-against http://localhost:8080
proxymock replay score proxymock/results/<replayed-run>

# Strict test config, tuned with drift between two replays of the same code
proxymock test-config new go-service --from standard
proxymock replay --in proxymock/recorded-baseline --test-against http://localhost:8080 --test-config go-service
proxymock drift --source proxymock/results/<replayed-run-1> --source proxymock/results/<replayed-run-2> --sensitivity strict

# The gate the script runs: a baseline once on known-good code, then every change against it
proxymock replay --in proxymock/recorded-baseline --test-against http://localhost:8080 \
  --test-config go-service --out proxymock/results/regress-base
proxymock replay --in proxymock/recorded-baseline --test-against http://localhost:8080 \
  --test-config go-service --baseline proxymock/results/regress-base --fail-on-new-mismatch

Where to go next​