Why REST API fundamentals review in Postman? - Purpose & Use Cases

The Big Idea

What if you could get all your daily data in seconds without lifting a finger?

The Scenario

Imagine you need to check the weather for 10 cities every day by opening different websites one by one and writing down the results on paper.

The Problem

This manual way is slow and tiring. You might make mistakes copying data, miss some cities, or waste lots of time repeating the same steps daily.

The Solution

REST APIs let you ask a computer directly for the data you want, like weather info, in a simple, automatic way. You can use tools like Postman to send requests and get answers fast without opening websites.

Before vs After

✗ Before

Open browser -> Search city weather -> Copy info -> Repeat for each city

✓ After

Send GET request to /weather?city=CityName -> Receive JSON data -> Repeat automatically for all cities

What It Enables

REST APIs make it easy to get and test data quickly and reliably, saving time and avoiding errors.

Real Life Example

A tester uses Postman to check if a shopping app's product list updates correctly by sending API requests instead of clicking through the app manually.

Key Takeaways

Manual checking is slow and error-prone.

REST APIs provide a fast, automatic way to get data.

Tools like Postman help test APIs easily and reliably.

Practice

1. Which HTTP method is typically used to retrieve data from a REST API without changing it?

easy

A. POST

B. GET

C. PUT

D. DELETE

Solution

1. Step 1: Understand HTTP methods

   GET is used to request data without modifying it, while POST, PUT, DELETE change data.

2. Step 2: Identify method for data retrieval

   Since we want to retrieve data without changes, GET is the correct method.

3. Final Answer:

   GET -> Option B

4. Quick Check:

   Retrieve data = GET [OK]

Hint: GET is for reading data, others modify it [OK]

Common Mistakes:

• Confusing POST with GET for data retrieval
• Using DELETE to get data
• Thinking PUT retrieves data

2. Which of the following is the correct way to set the HTTP method to POST in Postman?

easy

A. Add 'method: POST' in the Headers tab

B. Type 'POST' in the URL field

C. Select POST from the dropdown next to the URL input

D. Use the Body tab to set method to POST

Solution

1. Step 1: Locate HTTP method selector in Postman

   Postman has a dropdown menu next to the URL field to choose HTTP methods.

2. Step 2: Confirm correct method selection

   Selecting POST from this dropdown sets the request method properly.

3. Final Answer:

   Select POST from the dropdown next to the URL input -> Option C

4. Quick Check:

   Method dropdown sets HTTP method [OK]

Hint: Use dropdown near URL to pick method [OK]

Common Mistakes:

• Typing method name in URL field
• Trying to set method in Headers
• Confusing Body tab with method setting

3. What will be the status code returned by a successful DELETE request in a REST API?

medium

A. 404 Not Found

B. 201 Created

C. 200 OK

D. 204 No Content

Solution

1. Step 1: Understand DELETE success responses

   A successful DELETE often returns 204 No Content, meaning the resource was deleted and no content is returned.

2. Step 2: Compare other status codes

   200 OK means success with content, 201 Created is for new resource creation, 404 Not Found means resource missing.

3. Final Answer:

   204 No Content -> Option D

4. Quick Check:

   DELETE success = 204 No Content [OK]

Hint: DELETE success usually returns 204 No Content [OK]

Common Mistakes:

• Choosing 201 Created for DELETE
• Assuming 200 OK always returns content
• Confusing 404 with success

4. You send a POST request in Postman but get a 405 Method Not Allowed error. What is the most likely cause?

medium

A. The API endpoint does not support POST method

B. The URL is incorrect

C. The request body is empty

D. The server is down

Solution

1. Step 1: Understand 405 error meaning

   405 Method Not Allowed means the server recognizes the URL but the HTTP method used is not supported on that endpoint.

2. Step 2: Eliminate other options

   Incorrect URL usually gives 404, empty body usually does not cause 405, server down causes no response or 5xx errors.

3. Final Answer:

   The API endpoint does not support POST method -> Option A

4. Quick Check:

   405 = Method not allowed on endpoint [OK]

Hint: 405 means method not allowed on URL [OK]

Common Mistakes:

• Confusing 405 with 404 Not Found
• Assuming empty body causes 405
• Thinking server down causes 405

5. You want to test a REST API endpoint that updates user data. Which combination of HTTP method and Postman feature is best to use?

hard

A. PUT method with Body tab to send JSON data

B. GET method with Params tab to send JSON data

C. DELETE method with Headers tab to send JSON data

D. POST method with URL query parameters

Solution

1. Step 1: Identify method for updating data

   PUT is the standard HTTP method to update existing data in REST APIs.

2. Step 2: Choose Postman feature to send data

   The Body tab allows sending JSON data payload, which is needed to update user data.

3. Step 3: Evaluate other options

   GET does not update data, DELETE removes data, and URL query parameters are not suitable for sending JSON update data.

4. Final Answer:

   PUT method with Body tab to send JSON data -> Option A

5. Quick Check:

   Update data = PUT + Body JSON [OK]

Hint: Use PUT with Body for updates in Postman [OK]

Common Mistakes:

• Using GET to update data
• Sending JSON in URL parameters
• Confusing DELETE with update