Postman usecases tutorials from beginer to advance developer

 Postman is a popular tool for API testing and development. It simplifies the process of sending HTTP requests, examining responses, and automating workflows. Postman can be used for everything from simple API exploration to advanced API testing and automation. Below, I'll walk through various Postman use cases for developers at different levels, from beginner to advanced.

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1. Postman Use Cases for Beginners

1.1. Sending a Basic HTTP Request

Objective: Learn how to send a simple request to an API.

1. Open Postman and click "New" to create a new request.
2. Choose "Request" and give it a name.
3. Select the HTTP method (e.g., GET, POST, PUT, DELETE) from the dropdown.
4. Enter the URL for the API endpoint (e.g., https://jsonplaceholder.typicode.com/posts).
5. Click Send to execute the request.

Postman will show the response, including status code, headers, and body.

Use Case:

• Test simple GET requests to view API data.
• Validate API responses such as JSON, XML, or plain text.

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1.2. Sending Data with POST Requests

Objective: Learn how to send data using POST requests.

1. Select the POST method.
2. Enter the API endpoint (e.g., https://jsonplaceholder.typicode.com/posts).
3. Switch to the Body tab in Postman.
4. Select raw and choose JSON from the dropdown.
5. Enter JSON data to send in the request body:

   json
   {
     "title": "foo",
     "body": "bar",
     "userId": 1
   }
   

6. Click Send to submit the data.

Use Case:

• Test API endpoints that accept JSON or form data (e.g., user registration, form submissions).
• Check that the server correctly processes the submitted data.

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1.3. Testing API Response Codes and Response Time

Objective: Learn how to check HTTP status codes and response time.

1. Send a request (e.g., GET request to https://jsonplaceholder.typicode.com/posts).
2. Look at the Status code (e.g., 200 OK).
3. Check the Response Time (e.g., how long the server took to respond).

Use Case:

• Ensure that APIs return the correct status code (e.g., 200 for success, 404 for not found).
• Check how long the API takes to respond, useful for performance testing.

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2. Postman Use Cases for Intermediate Developers

2.1. Using Environment Variables

Objective: Learn to use environment variables for different environments (e.g., development, testing, production).

1. Click on the Environment dropdown on the top right and select Manage Environments.
2. Create a new environment (e.g., "Development").
3. Add a variable, e.g., base_url with the value https://jsonplaceholder.typicode.com.
4. Save the environment and select it from the dropdown.
5. In your request URL, use the variable: {{base_url}}/posts.
6. Click Send to execute the request.

Use Case:

• Use different environments (e.g., local, staging, production) without modifying the URL or credentials manually.
• Simplify requests by storing common variables like base URLs, tokens, and credentials.

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2.2. Sending Authentication Tokens

Objective: Learn how to send authentication tokens in requests.

1. In Postman, click on the Authorization tab for your request.
2. Choose Bearer Token as the type.
3. Enter the token (e.g., eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9...).
4. Send the request.

Alternatively, if your API uses basic authentication:

• Choose Basic Auth and enter your username and password.

Use Case:

• Test APIs with OAuth 2.0, JWT tokens, or Basic Authentication.
• Ensure correct API authorization for secure endpoints.

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2.3. Query Parameters and URL Variables

Objective: Learn to send query parameters and URL variables in requests.

1. For a GET request, add parameters to the URL (e.g., https://jsonplaceholder.typicode.com/posts?id=1).
2. You can also add query parameters in Postman by selecting the Params tab and entering key and value pairs.

For example, enter:

• Key: id
• Value: 1

Postman will automatically append the query parameter to the URL.

Use Case:

• Pass dynamic parameters (like user IDs, search terms) in the URL.
• Test APIs that support query parameters (e.g., pagination, filtering).

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2.4. Chaining Requests Using Postman

Objective: Learn to chain multiple requests together by using variables.

1. Create a request to log in to an API (e.g., sending a POST request to https://example.com/login with credentials).
2. In the response, store the authentication token by using Test Scripts. For example:

   javascript
   pm.environment.set('auth_token', pm.response.json().token);
   

3. In the next request, use the token:
   • Choose Authorization → Bearer Token.
   • Enter {{auth_token}} (Postman will replace this with the actual token).

Use Case:

• Automate workflows by chaining multiple requests (e.g., log in → get user data → make a transaction).
• Use environment variables for dynamic data between requests.

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3. Postman Use Cases for Advanced Developers

3.1. Automated Testing with Postman Collections

Objective: Learn how to write automated tests in Postman.

1. Create a request (e.g., GET request to https://jsonplaceholder.typicode.com/posts).
2. Click on the Tests tab and add a test script:

   javascript
   pm.test("Response code is 200", function () {
       pm.response.to.have.status(200);
   });
   
   pm.test("Response body contains 'userId'", function () {
       pm.response.to.have.jsonBody('userId');
   });
   

3. Click Send to execute the request. Postman will show the test results in the Test Results tab.

Use Case:

• Validate that APIs return the expected response (e.g., status code, headers, body).
• Write multiple tests (e.g., checking response time, JSON schema, etc.) for API correctness.

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3.2. Using Postman Monitors

Objective: Learn to run automated tests on a schedule using Postman Monitors.

1. Create a Postman Collection with the tests you want to run.
2. Go to the Postman Dashboard and select Monitors.
3. Click Create a Monitor, choose the collection, and set the frequency (e.g., every 1 hour).
4. Postman will run the collection at the scheduled time and provide results.

Use Case:

• Run automated API tests at regular intervals (e.g., every hour or once a day).
• Monitor API uptime and health over time.

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3.3. Mock Servers for API Testing

Objective: Learn to create mock APIs using Postman.

1. In Postman, go to the Mock Servers tab in the Postman Dashboard.
2. Click Create a Mock Server.
3. Select an existing collection or create a new one to define mock API responses.
4. You can now use the mock server’s URL (e.g., https://mockapi.postman.com) to simulate API requests.

Use Case:

• Test frontend applications when the backend API is not ready or still under development.
• Simulate responses from APIs for various scenarios.

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3.4. Automating API Documentation with Postman

Objective: Generate automated API documentation for your team.

1. Create a Postman Collection with all your requests.
2. Go to the Collection → Click on ... → Select Publish Docs.
3. Postman will generate a shareable API documentation URL.

Use Case:

• Automatically generate up-to-date API documentation for your team or external users.
• Share documentation links with stakeholders for easy access.

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4. Conclusion

Postman is a powerful tool that supports various stages of the API development lifecycle—from simple testing to full-fledged automated testing, API monitoring, and mock servers. Here's a summary of what you've learned:

1. Beginner: Sending HTTP requests, testing responses, and working with basic API requests.
2. Intermediate: Using environment variables, authentication, query parameters, and chaining requests.
3. Advanced: Automated testing, using monitors, mocking APIs, and generating API documentation.

By mastering Postman at these different levels, you can streamline your API development, testing, and collaboration processes, ensuring efficient and accurate development workflows.