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

## Summary
## Findings
## Structured outputs
## Coverage / rationale
## Assumptions
## Open questions
## Recommended next skill