Testing Express.js routes is a fundamental skill for developers working with APIs. To do this effectively, we need specialized software capable of sending various types of HTTP requests and inspecting server responses. Enter Postman, a powerful API testing tool that simplifies this process. In this chapter, we'll guide you through using Postman to test your Express.js routes step by step.

Step 1: Install Postman

If you haven't already, download and install Postman from Download Postman.

Step 2: Launch Postman

Open the Postman application on your computer.

Step 3: Create a New Request

1. Click on the "New" button located in the top-left corner;
2. Choose "Request" to create a new request.

Step 4: Name Your Request

Give your request a meaningful name. For instance, you can name it "GET Homepage."

Step 5: Select HTTP Method

In the request editor, select the appropriate HTTP method you want to test (e.g., GET, POST, PUT, DELETE) from the dropdown menu.

Step 6: Enter Request URL

1. In the URL field, enter the URL of your Express.js application, including the route you wish to test;
2. For example, if you want to test the GET homepage route, enter http://localhost:3000/.

Step 7: Send the Request

Click the "Send" button to send the request to your Express.js server.

Step 8: View Response

Postman will display the response from your server in the lower part of the window. Here, you can inspect the status code, response body, headers, and more.

Step 9: Test Other Routes

Create additional requests in Postman to test the other routes you've defined in your Express.js application. You can test POST, PUT, DELETE, and routes with URL parameters.

Step 10: Testing with Parameters

For routes that use URL parameters, you can include them in the URL in Postman. For instance, to test the route /users/123, enter http://localhost:3000/users/123.

Step 11: Inspect and Validate Responses

Carefully examine the responses you receive in Postman to ensure they match the expected behavior of your Express.js routes.

Step 12: Save Requests

Consider saving your requests in Postman collections for easy access and sharing with team members.

By mastering Postman, you'll streamline the process of testing and validating your Express.js APIs, ensuring they function flawlessly.