Agent Skills: BugMagnet

BugMagnet

Analyze a code module, write comprehensive edge-case tests, and document discovered bugs.

Attribution: Adapted from BugMagnet AI Assistant by Gojko Adzic (MIT License).

Usage

/bugmagnet <implementation-file-path>

Workflow

1. Read the implementation file and its existing tests
2. Identify untested edge cases, boundary conditions, and error paths
3. Write tests — run each one immediately after writing
4. When a test reveals a bug, document it as a skipped test (see format below), then explore nearby: bugs cluster together
5. Summarize findings

Do NOT modify the implementation file. Only write tests.

Bug Documentation Format

When a test reveals unexpected behavior, create a skipped test using the framework's skip mechanism with "- BUG" in the test name:

test.skip('normalizeEmail crashes on input without @ - BUG', () => {
    /*
     * ROOT CAUSE: destructuring email.split("@") fails when no @ present
     * CODE LOCATION: src/validator.ts:49
     * PROPOSED FIX: guard with if (!email.includes("@")) before split
     * EXPECTED: throws or returns input unchanged
     * ACTUAL: TypeError: Cannot read properties of undefined
     */
    expect(() => normalizeEmail("nodomain")).not.toThrow();
});

Every skipped BUG test must include: ROOT CAUSE, CODE LOCATION, PROPOSED FIX, EXPECTED vs ACTUAL.

Summary Format

After all tests are written, provide:

## Test Coverage Summary

**Tests Added:** N total
- Category 1 (X tests)
- Category 2 (Y tests)

**Results:** X passing, Y skipped (bugs)

**Bugs Discovered:**
1. Bug name — file:line
   - Root cause: ...
   - Proposed fix: ...