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The Ultimate Postman Tutorial for API Testing

The Ultimate Postman Tutorial for API Testing

The internet is increasingly built on APIs. In a world where more and more sites and applications are hosted on cloud platforms, APIs become the glue that holds everything together. Applications built on services based architectures use APIs to communicate with each other, and then of course there are the many public APIs that companies use to drive adoption and engagement of their tools. 

These APIs all need testing of course. However, unlike applications with a UI interface that can be automated using functional automation testing tools such as TestProject, APIs lack a graphical user interface (GUI) and are generally designed to be interacted with programmatically. Thus, it can be a bit intimidating to get started with this kind of testing. There are many tools that can help with API testing, but it can be hard to find a tool in that sweet spot between power and simplicity. Some API testing tools pack a big punch with a lot of features but are inherently tricky to use, while others are easy to pick up but don’t do everything you might want when it comes to an API testing tool.

So where do you find an API testing tool that navigates the balance between ease of use and depth of features? Enter Postman

What is Postman?

Postman has become the most popular API testing tool, as it is free, packed with powerful testing features, and that is also quite intuitive to use and get started with. In this Postman tutorial, we will show you just how easy it is to get started with API testing and how powerful Postman is for testing. We’ll walk you through everything from getting started with it, to using Postman in your CI and CD. 

Exploratory testing is just as important when testing APIs as when testing a UI, but since APIs are intended to be interacted with programmatically, they lend themselves well to test automation. This Postman tutorial will walk you through setting up effective API test automation. We’ll show you how to use Postman to create API mocks and how to organize and structure your data so that you can create effective test automation. We’ll also see how you can integrate your Postman tests directly into your CI/CD pipelines with Newman and explore the powerful scripting abilities built right into this tool.

Postman Tutorial Chapters

  1. Chapter 1 – Getting started with Postman for API Testing
    • What is an API?
    • What is Postman?
    • Postman Setup
    • Executing an API Request
    • API Testing with Postman
    • Summary
  2. Chapter 2 – Understanding API Authorization Options in Postman
    • Basic Auth
    • API Keys
    • OAuth 2
  3. Chapter 3 – Using Postman for Automation Testing
    • Organizing tests with Collections
    • Sharing data between tests in Postman
    • Variables
    • Collection Runner
  4. Chapter 4 – Using Test Scripts in Postman
    • Postman Test Scripts
    • Pre-request Scripts
    • Ready for Automating Requests
  5. Chapter 5 – Running Postman in CI using Newman
    • What is Newman?
    • Running Tests with Newman
    • Running Newman in CI
  6. Chapter 6 – Creating Mocks with Postman
    • What is Mock Data?
    • Create Mock Examples
    • Using a Postman Mock Server
    • Conclusion

Example API

This Postman tutorial will give you the footing that you need to get started with API testing. To get the most out of it though, don’t just read this – make sure you are practicing along with a real API. Most of the examples we will use will be based on the JSONPlaceholder API. This is a sample API that is specifically designed to be used for testing purposes. 

As you might have been able to guess, this tutorial will require you to have an up to date version of Postman installed. If you don’t yet have Postman you can download and install it from here. There will also be some command line calls and scripting throughout, but if you haven’t done much scripting before don’t worry, all code examples will be included in each of the chapters of this tutorial.

Well, we are ready to go now, so buckle up and get ready for a fun and informative ride into the land of API Testing with Postman! 🚀



About the author

Dave Westerveld

Dave Westerveld is an experienced tester who has been involved in various aspects of the testing role. As a strong exploratory tester, he has learned how to leverage many different tools to enhance his testing powers. He has also been involved in many automation projects including building out new automation frameworks. In addition he has helped transition several large and expensive automation suites into lighter weight, higher value systems. A speaker at several conferences, Dave also blogs about his thoughts and experiences at offbeattesting.com

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