How do I install the Bugmagnet skill?

Run npx skillmds@latest add pvillega/bugmagnet in your terminal (requires Node.js), paste this page's agent-chat prompt into Claude, Cursor, or any MCP-connected agent, or download the SKILL.md file and copy it into your agent's skills directory.

Is Bugmagnet safe to use?

This skill has not completed SkillMD's automated safety review yet. Capability flags: makes network calls. SkillMD never runs a skill's scripts for you; review the SKILL.md before installing.

Which AI agents work with Bugmagnet?

This skill is tagged as working with Claude Code, Claude.ai, OpenAI Codex. SKILL.md is an open format, so most agents that read a skills directory can load it too.

Is Bugmagnet free to use?

Yes. Installing skills from SkillMD is free, and the skill stays under its author's original license.

Who published Bugmagnet?

pvillega (@pvillega) published this skill. Their other Agent Skills are listed on their SkillMD profile.

Bugmagnet by pvillega — Agent Skill

Name: Bugmagnet
Rating: 4.666666666666667 (3 reviews)
Author: pvillega

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.

pvillega Updated Sep 10, 2026

File contents

BugMagnet

Systematic test coverage analysis and bug discovery.

Based on 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)

Detect language and testing conventions
Read implementation — public API, parameters, state, dependencies
Locate test file — if none exists, ask user about creating one
Run baseline coverage if tools available
Read existing tests — understand current coverage and patterns
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:

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.

Create minimal reproduction test.
Explore 2-3 adjacent code areas (bugs cluster).
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 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.

## 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

---name: bugmagnetdescription: 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.---# BugMagnetSystematic 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 conventions2. Read implementation — public API, parameters, state, dependencies3. Locate test file — if none exists, ask user about creating one4. Run baseline coverage if tools available5. Read existing tests — understand current coverage and patterns6. 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 constraintsCategorise: **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)

Frequently asked questions