API Testing
📌 Covered in this chapter:
Testing Routes & Controllers · Supertest · Mocking the Database · Integration Test DB
Test your Express routes and controllers end-to-end using Supertest, including mocked databases and authentication.
1API Testing — What You'll Learn
Test your Express routes and controllers end-to-end using Supertest, including mocked databases and authentication.
Here's everything this chapter covers, in the order you'll learn it:
- Testing routes
- Testing controllers
- Testing services in isolation
- Testing validation logic
- Testing authentication flows
- Testing database operations
- Mocking the database in unit tests
- Using Supertest for HTTP-level integration tests
- Setting up a dedicated integration test database
- Testing error responses
- Measuring test coverage
- Running tests in CI
2Working Example
💻 Example: API Testing
JavaScript
▶ Run in Compiler
import request from "supertest";
import app from "../src/app.js";
test("GET /api/courses returns 200", async () => {
const response = await request(app).get("/api/courses");
assert.equal(response.status, 200);
});3Best Practices & Common Pitfalls
💡 Key things to remember:
- Supertest lets you test real HTTP requests against your Express app in memory, without needing to actually start a server on a port.
❓ Frequently Asked Questions (FAQ)
Q What's the most important thing to understand about api testing?
Focus on: Testing Routes & Controllers · Supertest · Mocking the Database · Integration Test DB. These are the core building blocks this chapter's examples are built around, and they show up repeatedly in later chapters of this course.
Q Do I need external npm packages for api testing?
Only where explicitly shown in the code examples above (like Express, Zod, or Socket.IO) — otherwise, this chapter relies entirely on Node.js's own built-in capabilities.