Step-by-Step Tutorial to Automate API Testing in Postman with Venkatesh (Rahul Shetty)


In today's fast-paced development world, manual API testing just doesn’t cut it. Automation has become the cornerstone of efficient and reliable API testing. If you're just starting out or want to upgrade your skills, this step-by-step tutorial to automate API testing in Postman guided by concepts from experts like Venkatesh (Rahul Shetty) will help you master everything from basic request handling to Postman performance testing.

Whether you’re a beginner or an intermediate tester, this Postman tutorial for API testing is the perfect starting point. Let’s dive in.


What is API Testing?

API (Application Programming Interface) testing involves validating endpoints, data responses, status codes, and business logic of software services. It is crucial for ensuring the backend of your applications functions correctly.

Unlike UI testing, which checks the front-end, API testing digs deep into how components interact and exchange data making it faster, more reliable, and suitable for automation.


Why Use Postman for API Testing?

Postman is one of the most popular tools for API testing using Postman. It offers a clean UI, powerful scripting, automation features, and integration capabilities ideal for developers and testers alike.

Key Benefits:

  • Beginner-friendly

  • No-code and low-code automation

  • Detailed reporting

  • Support for variables and environments

  • Free API for Postman testing available

  • Strong community and learning resources like those by Venkatesh (Rahul Shetty)

 Tools Required - To follow this Postman tutorial for API testing, you all need:

  • Postman Desktop App

  • A free Postman account

  • Node.js and Newman (for running tests from the command line – optional but useful)

Getting Started: Setting Up Postman

Before automating your first API test, let’s walk through setting up your environment.

Step 1: Install Postman

  1. Go to postman

  2. Download the latest version.

  3. Sign up using your email

 Tip: For quick tests, you can use online Postman API testing

Step-by-Step Guide to Automate API Testing in Postman

Let’s automate API tests using a free API for Postman testing a fake REST API.

Step 2: Create a New Collection

Collections are containers for organizing API requests and tests.

  1. Click on “Collections” on the left sidebar.

  2. Click “+ New Collection”

  3. Name it: Postman Automation Testing

  4. Click Save

Step 3: Add a New Request

  1. Inside the collection, click “Add Request”

  2. Name it: Get User Data

  3. Choose GET as the method

  4. Save the request in your collection


Step 4: Write Your First Automated Test

Under the Tests tab of your request, add the following test script:

Click Send, then check the Test Results tab below the response. ✅

Automating API Tests with Postman Test Scripts

Step 5: Add More Assertions

Postman supports, making test logic powerful and readable.

Examples:


Step 6: Use Variables & Environments

Automated testing benefits from flexible test environments.

How to Set Up Environments:

  1. Go to Environments > Create New Environment

  2. Add variables:

  3. Save and activate it from the top-right dropdown

Step 7: Running Tests in Collection Runner

To run multiple requests automatically:

  1. Click the collection name

  2. Click Run

  3. Choose the environment

  4. Click Start Run

This triggers Postman automated testing, running each test and showing results in a clean report format.

Step 8: Automating with Postman Monitor

Monitors allow you to schedule automated tests.

  1. Open your collection

  2. Click Monitor

  3. Choose frequency

  4. Select environment and click Create

Now, your APIs are tested automatically on a schedule with no manual effort needed.

Step 9: Postman Automation API Testing with Pre-Request Scripts

Pre-request scripts allow dynamic data generation before API execution.

Example: Set a timestamp variable before making a POST request.

Step 10: Advanced Postman Performance Testing

While Postman isn’t a full-fledged performance tool like JMeter, you can still do basic Postman API performance testing by:

  • Running large iterations in Collection Runner

  • Measuring response time (available in Test Results)

  • Writing custom assertions:

Bonus: Automate API Testing in Postman using Newman (CLI)

Newman lets you run Postman collections from the terminal great for CI/CD pipelines.

Step-by-step:

Install Newman:

Export your collection from Postman:

  1. Click your collection

  2. (Optional) Use Jenkins or GitHub Actions to integrate into your automation pipeline.

This is one of the best approaches to enable continuous Postman automation API testing.


Postman Tutorial for Beginners: Best Practices

If you're new to this space, follow these tips from Rahul Shetty-style tutorials:

  • Start with simple

  • Use environments for scalability

  • Store dynamic data using variables

  • Write clear test cases and use comments

  • Reuse code snippets across requests

  • Make use of built-in snippets


Frequently Used Free APIs for Postman Testing

  1. JSONPlaceholder – Fake data REST API

  2. Reqres.in – A hosted REST-API for simulating user registration/login

  3. OpenWeatherMap – For weather info

  4. Cat Facts API – Fun API to test GET requests

  5. Postman Echo – Built-in Postman API for testing requests

These are ideal for practicing API testing Postman tutorial concepts.


Wrapping Up: Why Automate API Testing in Postman?

Automating API testing with Postman allows you to:

  • Detect issues early

  • Reduce manual effort

  • Validate integrations automatically

  • Ensure consistent performance

  • Save time in CI/CD pipelines

This Postman tutorial for beginners gave you a practical look into automation, variables, environments, monitors, and even Postman API performance testing. Guided by learning paths like those of Venkatesh (Rahul Shetty), you’re now well on your way to becoming an API automation expert.

Tips from Venkatesh (Rahul Shetty) on Postman API Testing

Venkatesh (Rahul Shetty), popularly known for his QA training, often emphasizes:

  • Learning by practice: Try building a mock server and testing it.

  • Script reuse: Save common tests as snippets.

  • Environment variables: Use environments to switch between development and production URLs.

  • Data-driven testing: Use CSV/JSON files in Collection Runner for testing with different datasets.

He recommends using Postman not just for manual testing, but also for automating repetitive tasks  especially regression and integration testing without writing full automation frameworks.


Final Thoughts

By following this step-by-step guide to automate API testing in Postman, you all gain real-world skills in modern API validation and automation. Continue practicing using free APIs for Postman testing, and try integrating your scripts into workflows using Newman and CI/CD tools.

Remember: automation isn't just about reducing manual tasks it's about delivering faster, smarter, and more reliable software.

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