Testing REST APIs with Postman

 🔍 Testing REST APIs with Postman: A Beginner’s Guide

Postman is one of the most popular tools for testing RESTful APIs—whether you’re a developer, tester, or QA engineer. This beginner-friendly guide will walk you through everything you need to send requests, analyze responses, and automate testing using Postman.


✅ What Is Postman?

Postman is a collaboration platform for API development that allows users to:


Send HTTP requests (GET, POST, PUT, DELETE, etc.)


Inspect API responses


Write test scripts


Automate API tests in collections


Simulate APIs using mock servers


🛠️ How to Install and Set Up Postman

Download Postman: https://www.postman.com/downloads/


Install it for your OS (Windows, macOS, or Linux)


Sign in or create a free account


💡 You can also use Postman Web if you don’t want to install it.


📬 Sending Your First API Request

Let’s walk through a simple GET request.


Example: Fetch users from a sample API

Endpoint:

https://jsonplaceholder.typicode.com/users


Steps:

Open Postman


Set method to GET


Enter the URL in the address bar


Click Send


✅ You should see a list of users returned in JSON format.


🧪 Testing Common HTTP Methods

1. GET – Fetch data

Used for reading resources


No body required


2. POST – Create data

Add new data to the server


json

Copy

Edit

{

  "name": "John Doe",

  "email": "john@example.com"

}

Set method to POST


Add body: raw → JSON


Add headers:


Content-Type: application/json


3. PUT / PATCH – Update data

PUT: full update


PATCH: partial update


4. DELETE – Remove data

Used to delete a resource by ID


🧪 Writing Tests in Postman

Postman lets you write JavaScript test scripts to validate responses.


Example: Basic Test

js

Copy

Edit

pm.test("Status code is 200", function () {

    pm.response.to.have.status(200);

});

More Useful Tests:

js

Copy

Edit

pm.test("Response time is less than 500ms", function () {

    pm.expect(pm.response.responseTime).to.be.below(500);

});


pm.test("Body contains user name", function () {

    var jsonData = pm.response.json();

    pm.expect(jsonData[0].name).to.exist;

});

📁 Using Collections

Collections are organized groups of API requests


Great for running a series of tests or workflows


You can share, document, and version-control your APIs


Steps to Create a Collection:

Click "New" → Collection


Add requests to the collection


Add pre-request scripts and test scripts


Save and run the collection


🔁 Automating with Collection Runner

You can run an entire collection using Collection Runner:


Click the collection


Click "Run"


Select environment (optional)


Add data file (for data-driven tests)


Click "Start Run"


📦 Environments and Variables

Use environments to manage different API base URLs, tokens, or IDs


Create global or environment-specific variables like:


js

Copy

Edit

{{base_url}} = https://jsonplaceholder.typicode.com

Then use in requests:


text

Copy

Edit

{{base_url}}/users

🚧 Mock Servers and Monitors

Mock Servers simulate endpoints during development


Monitors run your APIs at scheduled intervals for uptime and performance checks


🔐 Authentication in APIs

Postman supports:


Basic Auth


Bearer Tokens


OAuth 1.0/2.0


API Keys


Add these under the Authorization tab of your request or collection.


🧠 Tips for Effective API Testing in Postman

Use Pre-request Scripts to generate tokens or timestamps


Use Chaining: Pass data between requests using environment variables


Validate not only response codes but data types, values, and performance


Use Collection Runner + CSV for data-driven tests


Integrate with Newman (Postman’s CLI) for CI/CD pipelines


🔚 Conclusion

Postman makes REST API testing simple, powerful, and automated—even for beginners. With its user-friendly interface and rich scripting features, it's the go-to tool for API development and QA.


🧰 Resources

Postman Learning Center


Public Postman Workspace Examples


Newman CLI Tool for CI/CD

Learn Full Stack JAVA Course in Hyderabad

Read More

Integrating Thymeleaf with Spring Boot

Exception Handling in Spring Boot

Spring Boot Annotations You Must Know

Dependency Injection in Spring Framework

Visit Our IHUB Talent Training Institute in Hyderabad

Get Directions 

Comments

Post a Comment

Popular posts from this blog

How to Install and Set Up Selenium in Python (Step-by-Step)

 Here’s your step-by-step guide to installing and setting up Selenium in Python — perfect if you're just getting started with browser automation. 🚀 🐍 Step 1: Install Python If you haven’t already: Download Python: https://www.python.org/downloads/ Make sure to check the box "Add Python to PATH" during installation Verify installation: bash Copy Edit python --version pip --version 📦 Step 2: Install Selenium Library Open your terminal or command prompt and run: bash Copy Edit pip install selenium To verify: bash Copy Edit pip show selenium 🌐 Step 3: Download WebDriver for Your Browser Depending on what browser you want to automate: 🔹 Chrome: Download ChromeDriver: ➡️ https://sites.google.com/chromium.org/driver/ Make sure the driver version matches your installed Chrome version. 🔹 Firefox: Download GeckoDriver: ➡️ https://github.com/mozilla/geckodriver/releases Unzip and place the executable somewhere on your system, like: Windows: C:\WebDrivers\ Mac/Linux: /usr/local...
Read more

Tosca for API Testing: A Step-by-Step Tutorial

Tosca for API Testing: A Step-by-Step Tutorial Tricentis Tosca is a powerful and user-friendly test automation tool that supports a wide range of testing types — including API testing. With Tosca, you can easily design, automate, and execute API tests without writing any code. It supports REST, SOAP, and other service types, making it a great choice for end-to-end API validation. 🧰 What is Tosca API Testing? Tosca’s API testing allows testers to: Send requests (GET, POST, PUT, DELETE, etc.) Validate responses (status codes, body, headers) Chain requests and share data between them Perform security, load, and functional tests on APIs ✅ Step-by-Step Guide: Tosca API Testing 🔹 Step 1: Open Tosca and Create a Workspace Launch Tosca Commander Create a new workspace (or open an existing one) Choose the workspace type as Multi-user or Single-user based on your setup 🔹 Step 2: Add a New API Test Case Navigate to the Modules section. Right-click and choose Scan > API Scan. The API Scan wi...
Read more

Waits in Playwright: Explicit, Implicit, and Auto

 In Playwright (a powerful end-to-end testing framework), waiting mechanisms help ensure your scripts interact with elements only when they’re ready. Playwright handles waits more intelligently than older tools like Selenium, but understanding the types of waits—Explicit, Implicit, and Auto-waiting—is key for writing reliable tests. 🕰️ Waits in Playwright: Explicit, Implicit, and Auto ✅ 1. Auto-Waiting (Built-in) – Playwright’s Default Behavior What it is: Playwright automatically waits for elements to be actionable before performing actions (like click, type, fill, etc.). This is its most powerful feature. How it works: Waits for the element to be attached to the DOM Waits for the element to be visible Waits for the element to be enabled (not disabled) Waits for stable animation or layout Example: python Copy Edit await page.click('#submit-button') No need for a separate wait — Playwright will wait until the button is ready. Benefits: Reduces the need for manual waits More re...
Read more