Backend Test Writer

Generate comprehensive backend tests for MERN stack code. Analyzes file type, detects project conventions, produces tests that actually run.

Philosophy: Smart defaults, zero config. Detect everything from project.

Workflow

Copy and track progress:

• • Phase 0: Infrastructure check
• • Phase 1: Analyze target files
• • Phase 2: Generate tests
• • Phase 3: Report summary

Phase 0: Infrastructure Check

Before generating tests, verify setup:

1. •Check package.json for test framework (Jest/Vitest/Mocha)
2. •If none → prompt: "Set up Jest + Supertest?"
3. •Check for mongodb-memory-server (needed for integration tests)
4. •Detect test file convention (colocated vs __tests__/ vs tests/)

Stop if: No test framework and user declines setup.

Phase 1: Analyze Target Files

Override: User can specify --unit or --integration.

Phase 2: Generate Tests

Process files sequentially with progress. User can stop anytime.

Each test includes:

• •Proper imports for detected framework
• •Setup/teardown (DB connection, cleanup)
• •Comprehensive coverage:
  • •Success cases (happy path)
  • •Validation errors (400)
  • •Not found (404)
  • •Auth failures (401/403) if protected
  • •Edge cases (duplicates, empty, null)

Reference: See test-patterns.md for complete code examples.

Phase 3: Report

Generated: X test files
Coverage: Y test cases total
Next: Run `npm test` to verify

Quick Reference

Test Structure Pattern

describe('[Resource] [Method]', () => {
  describe('success cases', () => {
    it('should [expected behavior]', async () => {});
  });
  describe('validation errors', () => {
    it('should return 400 for [invalid case]', async () => {});
  });
  describe('edge cases', () => {
    it('should handle [edge case]', async () => {});
  });
});

Checklists

Infrastructure (Check First)

• • Test framework in package.json
• • Test script defined ("test": "jest")
• • Supertest installed (integration tests)
• • mongodb-memory-server installed (DB tests)

Per-File Generation

• • Check for existing tests first (gap analysis if found)
• • Correct imports for file type
• • Setup/teardown included
• • Happy path tested
• • Error cases tested (400, 404, 401)
• • Edge cases tested (domain-specific: date→DST/timezone, money→precision, etc.)
• • No secrets in assertions
• • Async/await handled properly
• • Priority assigned to each test (P0=critical, P1=important, P2=nice-to-have)
• • Test helper factories suggested for complex inputs

Common Mistakes

Guidelines

• •Don't generate tests for unread code
• •Don't skip infrastructure check
• •Don't generate only happy paths
• •Don't forget cleanup between tests

Reference Files

Load when implementing specific patterns: