Tutorial: Performing functional testing on APIs

1. Introduction

This tutorial aims to guide you through the process of performing functional testing on APIs. Functional testing is a type of testing that validates if your software is functioning correctly according to its design specifications.

By the end of this tutorial, you will learn how to:
- Understand the concept of API functional testing
- Prepare for API functional testing
- Perform API functional testing using Postman

No specific prerequisites are needed, but a basic understanding of APIs and HTTP methods will be beneficial.

2. Step-by-Step Guide

Functional testing for APIs involves checking if the APIs meet the expected behavior. We typically test the response code, response time, error codes (if any), and the result.

We'll use Postman for our API functional testing. Postman is a popular tool for API testing as it provides a user-friendly interface and several functionalities for handling different types of APIs.

Installing Postman

To install Postman, visit Postman's website and download the version suitable for your operating system.

Setting Up Postman

Once you have installed Postman, open it, and you will see a screen where you can either sign up or sign in. You can skip this step for now.

Making a GET Request

In Postman, you can make a GET request by entering the API endpoint URL in the "Enter request URL" box and selecting GET from the drop-down list.

3. Code Examples

There is no actual code involved in making a GET request with Postman. However, let's consider an example where you need to test a GET API endpoint https://jsonplaceholder.typicode.com/posts.

1. In Postman, select "GET" from the drop-down list.
2. Enter the URL https://jsonplaceholder.typicode.com/posts in the "Enter request URL" box.
3. Click on "Send".

After sending the request, you should receive a response in the lower section of the application window. This response includes the status of the request, time taken, size of the response, and the actual data.

4. Summary

In this tutorial, we've covered the following key points:

• The concept of API functional testing
• The process of setting up Postman for API testing
• Making a GET request using Postman

To expand your knowledge, you could explore:

• How to test other types of HTTP methods such as POST, PUT, and DELETE
• How to use Postman's features for more complex scenarios (e.g., chaining requests, running collections)

5. Practice Exercises

To further hone your skills in API functional testing, try the following exercises:

1. Test a POST API endpoint. You can use https://jsonplaceholder.typicode.com/posts for this exercise. This endpoint accepts a JSON object containing a title and body, both of type string, and a userId of type integer.

2. Test a PUT API endpoint. You can use https://jsonplaceholder.typicode.com/posts/1 for this exercise. This endpoint also accepts a JSON object with a title, body, and userId.

Remember, the key to mastering API functional testing is practice, so try to get your hands dirty with real testing as much as possible.