test-generation

type: skill name: Test Generation description: Generate comprehensive test cases for code skillSlug: test-generation phases: [E, V] generated: 2026-03-02 status: filled scaffoldVersion: "2.0.0"

Test Generation

When to Use

Activate this skill when generating test cases for existing or new code. Use it after implementing a feature, fixing a bug, or when increasing test coverage.

Instructions

1. Identify the test target: Determine what to test (service method, route handler, component, utility).
2. Choose the test framework:
   • NestJS backend → Jest with @nestjs/testing
   • Express backend → Jest with supertest
   • Next.js frontend → Vitest with React Testing Library
   • SvelteKit frontend → Vitest with @testing-library/svelte
   • Shared package → Jest
3. Set up test environment:
   • Use :memory: SQLite database for backend tests.
   • Mock Clerk auth middleware/guard (return a fake userId).
   • Mock API client functions for frontend component tests.
4. Write test cases following AAA pattern (Arrange, Act, Assert):
   • Happy path: Valid input produces expected output.
   • Validation errors: Missing required fields return 400.
   • Not found: Invalid IDs return 404.
   • Auth errors: Missing/invalid tokens return 401.
   • Edge cases: Empty search, special characters, max-length strings.
5. Name tests descriptively: it('should return 404 when franchise does not exist').
6. Legacy project policy: Prioritize writing tests for the active stack (NestJS backend, SvelteKit frontend). Do not write new tests for legacy projects (Express/Next.js) unless fixing a critical bug that requires a regression test. Test investment should go toward NestJS and SvelteKit.

Examples

NestJS Service Test

describe('FranchiseService', () => {
  it('should create a franchise with valid data', async () => {
    const dto: CreateFranchiseDTO = {
      name: 'Test Franchise',
      ownerName: 'John Doe',
      email: 'john@example.com',
    };
    const result = await service.create(dto);
    expect(result).toHaveProperty('id');
    expect(result.name).toBe('Test Franchise');
    expect(result.status).toBe('pending');
  });

  it('should return all franchises matching search term', async () => {
    const results = await service.findAll('São Paulo');
    expect(results.every(f => f.city === 'São Paulo')).toBe(true);
  });
});

Express Integration Test

describe('GET /api/franchises', () => {
  it('should return 200 with franchise list', async () => {
    const res = await request(app)
      .get('/api/franchises')
      .set('Authorization', 'Bearer test-token');
    expect(res.status).toBe(200);
    expect(res.body.data).toBeInstanceOf(Array);
  });
});