API Testing Skill

Running Tests

pnpm test # Run all tests pnpm test:watch # Watch mode pnpm test:coverage # With coverage pnpm -F @sgcarstrends/web test # Run web tests pnpm -F @sgcarstrends/web test:watch # Watch mode for web

Test Structure

apps/web/tests/ ├── setup.ts # Test setup ├── helpers.ts # Test utilities ├── queries/ # Query tests ├── components/ # Component tests └── utils/ # Utility tests

Testing API Routes

Basic Endpoint Test

import { describe, it, expect } from "vitest";

describe("GET /api/health", () => { it("returns 200 OK", async () => { const res = await fetch("http://localhost:3000/api/health"); expect(res.status).toBe(200); expect(await res.json()).toEqual({ status: "ok" }); }); });

Testing with Query Params

describe("GET /api/cars", () => { it("filters by month", async () => { const res = await fetch("http://localhost:3000/api/cars?month=2024-01"); expect(res.status).toBe(200); });

it("returns 400 for invalid month", async () => { const res = await fetch("http://localhost:3000/api/cars?month=invalid"); expect(res.status).toBe(400); }); });

Testing POST Endpoints

describe("POST /api/posts", () => { it("creates a new post", async () => { const res = await fetch("http://localhost:3000/api/posts", { method: "POST", headers: { "Content-Type": "application/json" }, body: JSON.stringify({ title: "Test", content: "Content" }), }); expect(res.status).toBe(201); }); });

Mocking

Mock Database

import { vi } from "vitest"; import { db } from "../src/config/database";

vi.spyOn(db.query.cars, "findMany").mockResolvedValue([ { make: "Toyota", model: "Corolla", number: 100 }, ]);

Mock External APIs

const mockFetch = vi.fn().mockResolvedValue({ ok: true, json: async () => ({ records: [] }), }); global.fetch = mockFetch;

Mock Redis

vi.mock("@sgcarstrends/utils", () => ({ redis: { get: vi.fn(), set: vi.fn(), del: vi.fn(), }, }));

Test Helpers

// apps/web/tests/helpers.ts export const createAuthHeader = (token: string) => ({ Authorization: Bearer ${token}, });

export const seedDatabase = async (data: any[]) => { await db.insert(cars).values(data); };

export const clearDatabase = async () => { await db.delete(cars); };

Best Practices

• Isolate tests - Each test should be independent

• Test error cases - Test both happy and error paths

• Use mocks - Mock external dependencies

• Clean up - Reset state in afterEach

• Descriptive names - Clear test descriptions

• Coverage goals - Aim for 80%+ coverage

Coverage Configuration

// vitest.config.ts export default defineConfig({ test: { coverage: { provider: "v8", thresholds: { lines: 80, functions: 80, branches: 80 }, }, }, });

References

• Vitest: https://vitest.dev

• Next.js Testing: https://nextjs.org/docs/app/building-your-application/testing