# Test your guard by breaking it first

Status: DRAFT, nothing posted. Single-image infographic, 2 slide(s), no cover. Idea IB-1087.

## What it shows

Rule 19 clause 4: no verifier ships without a negative control. The flow is the red then green test, and slide 2 contrasts an untested guard with a tested one.

No numbers appear on the slides unless listed below.

## Claims and sources

| Claim | Source (agency-operator unless stated) | Read-date |
|---|---|---|
| No verifier ships without a negative control; a check never seen to fail is not a check | `.claude/rules/19-verify-before-assert.md` | 2026-10-11 |
| Run its red case, then its green case, and add the pair to the selftest or it does not merge | `.claude/rules/19-verify-before-assert.md` | 2026-10-11 |
| Every hook ships with red and green selftests | `.claude/rules/19-verify-before-assert.md` | 2026-10-11 |