Mocking database calls in Express - Mini Project: Build & Apply

Mocking database calls in Express

📖 Scenario: You are building a simple Express server that fetches user data from a database. To test your server without a real database, you will mock the database calls.

🎯 Goal: Create an Express server with a mocked database call that returns user data. You will set up the data, configure a mock function, implement the route using the mock, and complete the server setup.

📋 What You'll Learn

Create a mock user data array called users with exact user objects

Create a mock function called getUsersFromDb that returns the users array

Create an Express route /users that uses getUsersFromDb to send user data as JSON

Complete the Express server setup with app.listen on port 3000

💡 Why This Matters

🌍 Real World

Mocking database calls helps developers test server routes without needing a real database connection. This speeds up development and testing.

💼 Career

Backend developers often mock database calls to write unit tests and develop APIs before the database is ready or to isolate code during testing.

1

DATA SETUP: Create mock user data

Create a constant array called users with these exact objects: { id: 1, name: 'Alice' } and { id: 2, name: 'Bob' }.

Express

// Create the mock user data array called users
// Your code here

Need a hint?

Use const users = [ ... ] with two objects inside the array.

2

CONFIGURATION: Create mock database function

Create a function called getUsersFromDb that returns the users array.

Express

const users = [
  { id: 1, name: 'Alice' },
  { id: 2, name: 'Bob' }
];

// Create the mock function getUsersFromDb
// Your code here

Need a hint?

Define a function named getUsersFromDb that returns the users array.

3

CORE LOGIC: Create Express route using mock function

Import Express, create an app with express(), and add a GET route /users that calls getUsersFromDb() and sends the result as JSON with res.json().

Express

const users = [
  { id: 1, name: 'Alice' },
  { id: 2, name: 'Bob' }
];

function getUsersFromDb() {
  return users;
}

// Import express, create app, and add GET /users route
// Your code here

Need a hint?

Use require('express') to import Express, create app, and define the GET route with app.get.

4

COMPLETION: Start the Express server

Add app.listen to start the server on port 3000.

Express

const express = require('express');
const users = [
  { id: 1, name: 'Alice' },
  { id: 2, name: 'Bob' }
];

function getUsersFromDb() {
  return users;
}

const app = express();

app.get('/users', (req, res) => {
  const data = getUsersFromDb();
  res.json(data);
});

// Start the server on port 3000
// Your code here

Need a hint?

Use app.listen(3000) to start the server on port 3000.