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QA Guide to REST API Testing for Beginners

Name: QA Guide to REST API Testing for Beginners
Rating: 4.5 (350 reviews)

Get skilled at using Postman and Fiddler to create, call, and test REST APIs for software testing

Highest Rated

Created byGlitch IT System

Last updated 4/2026

English

What you'll learn

You will learn what APIs are and how they work
You will be skilled at using Postman and Fiddler to create, issue requests, and test APIs
You will learn how to use Fiddler to capture, view, replay, and manipulate web traffic
You will be able to read and create JSON data
You will learn some javaScript

Course content

9 sections • 58 lectures • 5h 26m total length

Introduction0:38
How to get help3:15

Introduction to javaScript and JSON data2:14
Explore javascript and json data (javascript object notation) to understand how json relates to API testing, using the browser console for hands-on exercises and refreshing the console between tasks.
Datatypes10:39
Variables14:53
Arrays6:15
Objects and JSON10:04
Accessing object values9:11
Learn to access object properties and array elements with dot notation and indexing, including nested objects and first array items, using practical examples from the lecture.

Intro to Postman1:18
Postman installation4:01
Create a request10:10
Collections12:21
Path parameters6:18
Query parameters6:01
POST, PUT, and PATCH requests18:32
DELETE request1:10
Variables6:16
API key6:21
Environment variables6:38
Explore postman's environment variables to switch between dev, qa, staging, and production by defining a base URL and referencing it with curly braces; customize dynamic values without hard coding.
Headers1:34

Intro to Postman API testing1:30
Learn how to test an API with Postman, run tests automatically, access the test tab for saved requests, and explore built-in snippets, docs, and scripts to implement common test scenarios.
Testing for status codes9:41
Testing for body content11:24
Using variables in tests6:06
Learn to use environment and global variables in REST API tests, insert them into tests with curly braces, and validate responses by string matching.
Testing for response time4:41
Testing for headers4:15
Challenge Project: Testing the PokeAPI5:16
Challenge Solution: Testing the PokeAPI54:27

Intro to Fiddler0:53
A quick note about Fiddler0:30
Fiddler installation5:49
Install fiddler by downloading the Windows installer, choose defaults, then configure http/https settings, decrypt HTTPS traffic, and trust the root certificate to view all traffic.
Understanding the session output4:24
Inspectors3:42
Configuration the session data4:34
Customize the session data view by adding and arranging columns like session timer, client begin response, client response, and request method to monitor overall elapsed time and specific timings.
Filtering requests5:50
Session timeline2:41
Learn to use the session timeline to analyze performance by selecting sessions, refreshing, and double-clicking items to view transactions, durations, and filters for identifying slow steps and optimizing load times.
Replaying requests2:17
Simulating network speeds3:14
Simulate varying network speeds, including modem-like delays, to test how your app handles API calls on slow connections and maintains stability with caching and retry messaging.
Auto-responder8:11

Requirements

Basic understanding of computers and web browsers
Basic knowledge of testing practices is helpful, but not required
PC or Mac computer
All software used in the course is freely available on the internet

Description

Welcome!

This is the third course in my "QA Guide" series. Application QA Engineers are high on the list of great jobs that can earn you over $100k a year. Take the next step to achieve your maximum earning potential.

What are APIs? And how do we test them?

APIs are an extremely important part of the applications that we use everyday. There are APIs being called every time you open an app on your phone, search for products on the web, or play a song from your Alexa.

If your team is developing a mobile app or web application, there are going to be APIs involved. You need to be able to understand what APIs are, how they work, and how to test them.

Are you ready to work with APIs?

In this course you will learn everything that you need to know to get started with REST API testing.

The course starts with API basics. Here you will learn what an API is and how they work.

I will be covering several tools along the way to help you validate and format APIs so that you can quickly and easily understand the purpose and content.

You will learn some javaScript which is essential when working with REST APIs.

The bulk of the course will be through exercises. We will use Postman to generate API requests. Then we will use Postman to test the requests that we created.

Finally, we will be using Fiddler to capture, view, and manipulate API Traffic.

Get started now!

Who this course is for:

You want to know more about APIs
You want to learn how to test APIs
You want to learn how to create re-usable test cases for APIs
You want to be able to read and create JSON data
You want to learn some javaScript

QA Guide to REST API Testing for Beginners

What you'll learn

Explore related topics

Course content

Introduction2 lectures • 4min

API Basics8 lectures • 18min

Working with JSON with Sublime Text6 lectures • 18min

javaScript and JSON data6 lectures • 53min

API Playback Tool - Postman12 lectures • 1hr 21min

Postman Testing8 lectures • 1hr 37min

Browser Developer Tools3 lectures • 12min

API Proxy Tool - Fiddler11 lectures • 42min

Wrap Up2 lectures • 1min

Requirements

Description

Who this course is for: