Of course! This is a comprehensive Postman tutorial for beginners. We'll start from the very basics and build up to key concepts.

What is Postman?

Postman is a powerful API platform used for building and using APIs. In simple terms, it's a tool that lets you send requests to a web server and get responses back, without having to write code for a full application. It's used by developers and testers for:

• API Testing: Checking if an API works as expected.


• API Development: Building and debugging APIs.


• Documentation: Creating and sharing API documentation.


• Mock Servers: Simulating an API before the real one is built.


• Automation: Running collections of requests automatically.

Step 1: Installation and Setup

• Download Postman: Go to https://www.postman.com/downloads/ and download the app for your operating system (Windows, Mac, Linux). The desktop app is recommended over the web version for full functionality.


• Sign Up / Log In: You can create a free Postman account. This allows you to save your work and sync it across devices.

Step 2: Your First API Request (GET)

We'll start with a simple public API that requires no authentication.

• Open a New Tab: Click the + button to open a new request tab.


• Select the HTTP Method: From the dropdown left of the URL bar, select GET.


• Enter the Request URL: Type the following URL:

• Click "Send": Hit the big blue Send button.

Congratulations! You've made your first API call. You should see a 200 OK status and a JSON response in the bottom panel showing the details of a post.

Step 3: Understanding the Postman Interface

Let's break down the key areas you just used:

• HTTP Method: GET, POST, PUT, DELETE, etc. Defines the type of action you want to perform.


• Request URL (Endpoint): The address of the API you want to talk to.


• Params: Used to send query parameters (e.g., ?userId=1 in a URL).


• Headers: Key-Value pairs that send additional information about the request (e.g., Content-Type: application/json).


• Body: Where you put the data you want to send to the server (used for POST, PUT, etc.).


• Response Section:


• Status: The HTTP status code (e.g., 200 OK, 404 Not Found, 500 Internal Server Error).


• Time: How long the request took.


• Size: The size of the response.


• Body: The actual data returned by the server. You can view it as Pretty (formatted), Raw (plain text), or Preview (for HTML).

Step 4: Making a POST Request

A GET request retrieves data. A POST request creates new data.

Let's create a new post on the same mock API.

• Change the Method: Select POST from the dropdown.


• Change the URL: Use https://jsonplaceholder.typicode.com/posts. (Notice we are not targeting a specific ID like /1).


• Set Headers: Go to the "Headers" tab. Add a new key:


• Key: Content-Type


• Value: application/json


• Set Body: Go to the "Body" tab.


• Select the raw radio button.


• From the dropdown next to "raw", select JSON.


• Enter the following JSON data:

{
      "title": "My First Post via Postman",
      "body": "This is the body of the post created by a beginner!",
      "userId": 1
    }

• Click Send.

Step 5: Organizing Requests with Collections

You don't want to lose your requests. Collections are folders to group and save your API requests.

• Create a Collection: On the left sidebar, click Collections > +.


• Name It: Call it "My First API Tests".


• Save Your Requests: Go back to your request tabs. Click the Save button, give your request a name (e.g., "Create New Post"), and select your new collection to save it into.

Step 6: Using Variables

Variables make your requests dynamic and reusable. The most common is the Collection Variable for a base URL.

• Edit Your Collection: Hover over your collection, click the ... (three dots) and select Edit.


• Go to the Variables Tab: We'll add a variable for our base URL.


• Add a Variable:


• Variable: base_url


• Initial Value: https://jsonplaceholder.typicode.com


• Current Value: (Leave it the same for now).


• Click Update.


• Use the Variable in a Request: Open one of your saved requests. Change the URL from the full address to use the variable.


• Old URL: https://jsonplaceholder.typicode.com/posts


• New URL: {{base_url}}/posts

Step 7: Writing Simple Tests (Tests Scripts)

Postman has a powerful feature where you can write JavaScript code to automatically verify your API responses.

• Go to the "Tests" Tab: In your request, this tab is next to "Body".


• Write a Test: Let's write a test to check if the status code is 200. On the right, you'll see snippets. Click on "Status code: Code is 200".

pm.test("Status code is 200", function () {
        pm.response.to.have.status(200);
    });

• Send the Request. After you get the response, go to the "Test Results" tab in the response section. You should see 1 test passing.

Next Steps & Best Practices

You've learned the core workflow! Here's where to go from here:

• Environments: Use environments to manage variables for different setups (e.g., devbaseurl, prodbaseurl).


• Authentication: Explore the "Authorization" tab to learn how to handle API Keys, Bearer Tokens, and OAuth.


• Running Collections: Click the "Run" button on your collection to run all requests in a sequence. This is how you automate your API tests.


• Documenting Your API: Use the description fields in your collections and requests to document what each API does. This is great for sharing with your team.

Summary of Common HTTP Methods in Postman