# Fault Based Test Ideator

> fault-based-test-ideator

- Skill: `45ck/fault-based-test-ideator` (Agent Skill)
- Install (CLI): `npx skillmds@latest add 45ck/fault-based-test-ideator`
- Raw SKILL.md: https://api.skillmd.com/api/skills/45ck/fault-based-test-ideator/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: 45ck (https://skillmd.com/u/45ck)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/45ck/fault-based-test-ideator

---

# fault-based-test-ideator

## Purpose
Generate tests based on likely developer mistakes, common defect patterns, and known fragility in the design or code.

## Trigger this skill when
- You need disciplined test design rather than ad hoc case generation.
- You need to justify why a test set is sufficient.
- You want a reusable artifact that can feed automation later.

## Expected inputs
- requirements or code
- defect history if available
- risk hotspots
- common bug patterns

## Deliverables
- fault hypotheses
- targeted tests
- bug pattern mapping
- risk-ranked defect probes

## Operating procedure
1. Identify likely mistake patterns such as off-by-one, null handling, logic inversion, stale state, and incorrect defaults.
2. Map each fault hypothesis to a focused test or probe.
3. Rank hypotheses by plausibility and impact.
4. Prefer defect-seeking tests over generic repetition.

## Quality gates
- Be explicit about infeasible, unreachable, or assumption-heavy cases.
- Prefer lean, justified test sets over exhaustive-looking noise.
- Keep expected outcomes observable and tied back to rules or logic.
- Show why each test exists, not just the test data.

## Handoff targets
- negative-test-designer
- coverage-goal-planner
- review or inspection packs later

## Output style
- Be explicit about uncertainty, infeasibility, and residual risk.
- Prefer compact, explainable artifacts over bloated lists.
- Tie tests back to rules, logic, or structure.
- Make expected outcomes observable.

## Failure modes to avoid
- Do not invent exotic faults while ignoring common ones.
- Do not produce unranked lists with no rationale.
- Do not omit the link from fault hypothesis to concrete test.

## Minimum output skeleton
```md
## Summary
## Findings
## Structured outputs
## Coverage / rationale
## Assumptions
## Open questions
## Recommended next skill
```