# Bugmagnet

> Discover edge cases and test coverage gaps through systematic analysis. Use when analysing TEST coverage, hunting for edge cases, or when code-reviewer identifies test gaps. Triggers on "find holes in my tests", "what could go wrong", "is this well tested", "what edge cases am I missing". When to pick bugmagnet vs alternatives: - find-bugs → branch-diff bug scan (uses git diff, scoped to recent changes) - security-review → OWASP-categorised vulnerability audit - code-review → PR-style review with comment threads - ct:bugmagnet → test-gap edge-case discovery (THIS one) If the question is "are my TESTS missing cases?", use bugmagnet. Otherwise pick one of the three above.

- Skill: `pvillega/bugmagnet` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add pvillega/bugmagnet`
- Raw SKILL.md: https://api.skillmd.com/api/skills/pvillega/bugmagnet/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Product & Planning
- Author: pvillega (https://skillmd.com/u/pvillega)
- Updated: 2026-09-10
- Page: https://skillmd.com/skills/pvillega/bugmagnet

---


# BugMagnet

Systematic test coverage analysis and bug discovery.

Based on [gojko/bugmagnet-ai-assistant](https://github.com/gojko/bugmagnet-ai-assistant).

## Workflow

```
🔍 ANALYSE  → Understand code and existing tests
📊 GAP      → Identify missing coverage
✍️ WRITE    → Implement tests iteratively
🔬 ADVANCED → Deep edge case exploration (optional)
📋 SUMMARY  → Document findings and bugs
```

**Interactive mode (default):** STOP and wait for user confirmation between phases.
**Autonomous mode:** When invoked by another agent (e.g. code-reviewer), skip all STOP points and proceed through all phases automatically. Present the full summary at the end instead of pausing for input.

---

## Phase 1: Analysis (🔍 ANALYSE)

1. Detect language and testing conventions
2. Read implementation — public API, parameters, state, dependencies
3. Locate test file — if none exists, ask user about creating one
4. Run baseline coverage if tools available
5. Read existing tests — understand current coverage and patterns
6. Ask user: "Are there additional files I should review?"

**STOP** — Wait for user input. *(Skip in autonomous mode.)*

---

## Phase 2: Gap Analysis (📊 GAP)

Evaluate missing coverage using [edge-cases.md](references/edge-cases.md):

- Boundary conditions, error paths, state transitions
- Complex interactions, domain-specific edge cases
- Violated domain constraints

Categorise: **High** (core, errors, boundaries) → **Medium** (interactions, state) → **Low** (rare, performance). Present analysis with specific examples.

**STOP** — Ask user which tests to implement. *(Skip in autonomous mode — implement all high-priority tests.)*

---

## Phase 3: Test Implementation (✍️ WRITE)

For each test, highest priority first: write single test (or 2-3 related), name describes outcome ("returns X when Y"), run immediately. **Maximum 3 attempts per test** — document and move on.

→ While writing tests, actual bug discovered in implementation → STOP. Do NOT fix the bug.
  1. Create minimal reproduction test.
  2. Explore 2-3 adjacent code areas (bugs cluster).
  3. Document in skipped test: brief description, root cause, code location, expected vs actual, proposed fix.
→ Return to test writing.

**STOP** — Ask user if they want advanced coverage. *(Skip in autonomous mode — proceed to advanced if high-priority gaps remain.)*

---

## Phase 4: Advanced Coverage (🔬 ADVANCED)

Create separate test suite: "bugmagnet session \<date\>"

Work through [edge-cases.md](references/edge-cases.md) comprehensively — complex interactions, error handling, numeric/date/string/collection edge cases, state transitions, domain-specific cases.

---

## Phase 5: Summary (📋 SUMMARY)

Keep summary under 30 lines. No preamble.

```markdown
## Test Coverage Summary

**Tests Added:** X total (Y passing, Z skipped/bugs)

**Bugs Discovered:**
1. Bug name — file:line — root cause — proposed fix
```

## Reference Files

- [Edge Case Checklist](references/edge-cases.md)