Postman - Working, HTTP Request & Responses

Postman is a versatile platform that helps developers and testers streamline API workflows. It acts as a bridge between the client and the server, allowing users to build and analyze requests, inspect detailed responses, and manage different testing scenarios in one place.

Key Features:

• Visual Interface: Intuitive workspace for creating and organizing API requests.
• Debugging Support: Inspect request-response cycles with headers, payloads, and status codes.
• Data Handling: Use variables and scripts to customize requests dynamically.
• Team Integration: Collaborate by sharing collections, reports, and API documentation.
• Automation Tools: Schedule or trigger test workflows for faster validation.

Postman Installation

You can install the postman from the link Postman. This tool provides a collection of API calls, and you need to follow these API calls for testing APIs of the application. You will find a dropdown list with multiple methods. 

Configure the Request

You can select one of the methods from the given dropdown list. You will also have to include more information depending on the API call. This information are set as Authorization, Header, or body information. You just need to select one of the methods and send the request and get the response back.

Environment Variables in Postman

Some requests in POSTMAN require some specific information. You can make changes to these variables all at once instead of changing the variables in the endpoint manually. In the top right corner, you will get the option to set the environment variable. You can follow the steps given below to set the environment variable. 

1. In the top right corner click on Manage Environment from Settings.
2. Click on ADD button.
3. Mention the Name of the environment.
4. Mention key and value. This will be used as a variable in the collection late

Add Collection

Collections are groups of related API requests that help keep testing organized. You can create your own, import collections from others, or export them to share with teammates. This makes reusing requests and collaborating on API testing much easier.

HTTP Request in Postman

You make HTTP calls sending the HTTP Request. In HTTP request method includes Request Method, Request URL, Request Headers, Request Body, Pre-request Script, and Tests.

Request Methods.

• GET: Retrieve data from the server.
• POST: Send data to create resources on the server.
• PUT: Update existing resources.
• PATCH: Make partial updates to resources.
• DELETE: Remove resources from the server.

When creating a request, you can include:

• URL / Endpoint: The API address you are sending the request to. It defines which resource you want to access.
• HTTP Method: The action you want to perform on the resource, such as GET, POST, PUT, PATCH, or DELETE.
• Headers: Metadata that provides additional information about the request, like Content-Type, Authorization, or custom headers required by the API.
• Body: Data sent to the server in requests like POST, PUT, or PATCH. Formats include JSON, XML, form-data, or plain text.
• Params (Query Parameters): Key-value pairs appended to the URL to filter, sort, or customize the request.
• Authorization: Credentials or tokens required to access protected resources, such as Bearer tokens, API keys, or OAuth.
• Pre-request Scripts: Optional JavaScript code that runs before the request is sent, useful for setting dynamic variables or authentication tokens.
• Tests / Scripts: JavaScript code executed after receiving a response to validate data, status codes, or automate workflows.

Example:

In the example we want to get user details from an API:

• Method: GET
• URL:https://api.example.com/users/123
• Headers:Authorization: Bearer <token>

HTTP Response in Postman

After sending a request, Postman displays the HTTP response, providing detailed information about the server’s reply. Understanding these components is essential for testing and debugging APIs effectively..

• 200 OK – Request succeeded.
• 201 Created – Resource successfully created.
• 204 No Content – Request succeeded but no content returned.
• 400 Bad Request – Client-side error, usually due to invalid input.
• 401 Unauthorized – Authentication required or failed.
• 403 Forbidden – Access denied despite authentication.
• 404 Not Found – Endpoint or resource doesn’t exist.
• 500 Internal Server Error – Server encountered an error.
• 502 Bad Gateway / 503 Service Unavailable – Server issues or downtime.

Benefits of Using Postman

• Simplifies API Testing – Test APIs effortlessly without building separate client applications, making development faster and less error-prone.
• Accelerates Development – Quickly send requests, inspect responses, and debug APIs, reducing time spent on trial-and-error testing.
• Enables Automation – Automate tests, validate responses, and monitor APIs to ensure reliability and consistency across environments.
• Enhances Collaboration – Share collections, test scripts, and documentation with team members for smooth teamwork and consistent workflows.
• Improves Productivity – Features like environments, variables, and pre-request scripts streamline repetitive tasks, saving time and effort.