What APIs are and why testing them matters in Postman - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does API stand for and what is its basic purpose?

API stands for Application Programming Interface. It allows different software programs to talk to each other and share data or functions.

beginner

Why is testing APIs important in software development?

Testing APIs ensures that the software parts communicate correctly, data is accurate, and the system works as expected before users see it.

beginner

Name one common tool used for API testing.

Postman is a popular tool used to send requests to APIs and check their responses easily.

beginner

What is a simple real-life example of an API?

When you use a weather app, it gets weather data from a server using an API. The app and server talk through the API.

beginner

What can happen if APIs are not tested properly?

If APIs are not tested, the app might show wrong data, crash, or not work well, causing a bad experience for users.

What is the main role of an API?

A To store data permanently

B To design the user interface

C To allow software to communicate with each other

D To run the operating system

APIs let different software programs exchange information and work together.

Which tool is commonly used for testing APIs?

A Visual Studio Code

B Photoshop

C Excel

D Postman

Postman is designed to send requests to APIs and check their responses.

Why should APIs be tested before releasing software?

A To ensure data is correct and communication works

B To improve screen colors

C To speed up the internet

D To change the software license

Testing APIs helps catch errors in data and communication early.

What might happen if an API is not tested?

A The app may show wrong data or crash

B The app will load faster

C The app will have better graphics

D The app will use less battery

Untested APIs can cause errors and crashes in the app.

Which of these is an example of an API in daily life?

A Typing on a keyboard

B A weather app getting data from a server

C Watching a video

D Charging a phone

The weather app uses an API to get weather information from a server.

Explain what an API is and why testing it is important.

Think about how software parts talk and why we check their conversation.

Describe a simple real-life example of an API and how testing helps in that context.

Consider apps you use daily that get data from somewhere else.

Practice

1. What is an API in simple terms?

easy

A. A programming language

B. A type of computer virus

C. A way for different software to talk to each other

D. A hardware device

Solution

1. Step 1: Understand the role of APIs

   APIs allow different software programs to communicate and share data.

2. Step 2: Eliminate incorrect options

   Options A, B, and D describe unrelated concepts like programming languages, viruses, or hardware.

3. Final Answer:

   A way for different software to talk to each other -> Option C

4. Quick Check:

   API = software communication [OK]

Hint: APIs connect software systems to share data [OK]

Common Mistakes:

• Confusing API with programming language
• Thinking API is hardware
• Believing API is a virus

2. Which of the following is the correct way to send a GET request in Postman?

easy

A. Write GET in the body and click Send

B. Select GET method, enter URL, click Send

C. Select POST method, enter URL, click Send

D. Enter URL in headers and click Send

Solution

1. Step 1: Identify the correct HTTP method usage

   GET requests are sent by selecting GET method, entering the URL, and clicking Send in Postman.

2. Step 2: Check incorrect options

   Write GET in the body and click Send wrongly puts GET in the body; C uses POST method; D misuses headers for URL.

3. Final Answer:

   Select GET method, enter URL, click Send -> Option B

4. Quick Check:

   GET request = method + URL + Send [OK]

Hint: GET requests need method, URL, then Send [OK]

Common Mistakes:

• Putting method name in body
• Using wrong HTTP method
• Entering URL in headers

3. In Postman, if you send a request and receive status code 404, what does it mean?

medium

A. The requested resource was not found on the server

B. The server is working fine and returned data

C. The request was successful with no content

D. The server encountered an internal error

Solution

1. Step 1: Understand HTTP status codes

   Status code 404 means the server could not find the requested resource (page or data).

2. Step 2: Match code to meaning

   The requested resource was not found on the server correctly describes 404; B describes success (200 OK); C is 204; D is 500 error.

3. Final Answer:

   The requested resource was not found on the server -> Option A

4. Quick Check:

   404 = Not Found [OK]

Hint: 404 means resource missing on server [OK]

Common Mistakes:

• Confusing 404 with success codes
• Thinking 404 means server error
• Mixing 404 with no content status

4. You sent a POST request in Postman but got a 400 Bad Request error. What is the most likely cause?

medium

A. The request body is missing or malformed

B. The server is down

C. The URL is correct but method is GET

D. The response data is too large

Solution

1. Step 1: Understand 400 Bad Request meaning

   400 error means the server could not understand the request due to bad syntax or missing data.

2. Step 2: Identify likely cause in POST request

   POST requests usually require a body; if missing or malformed, server returns 400.

3. Final Answer:

   The request body is missing or malformed -> Option A

4. Quick Check:

   400 = Bad Request due to bad input [OK]

Hint: 400 error means bad or missing request data [OK]

Common Mistakes:

• Assuming server is down for 400 error
• Confusing method mismatch with 400
• Thinking response size causes 400

5. Why is it important to test APIs using tools like Postman before integrating them into an application?

hard

A. To avoid writing any code in the application

B. To make the API run faster on the server

C. Because APIs never change once created

D. To ensure the API responds correctly and handles errors gracefully

Solution

1. Step 1: Understand the purpose of API testing

   Testing APIs ensures they return correct data and handle errors well before using them in apps.

2. Step 2: Evaluate incorrect options

   A is wrong because testing doesn't replace coding; C is false as APIs can change; D is unrelated to testing.

3. Final Answer:

   To ensure the API responds correctly and handles errors gracefully -> Option D

4. Quick Check:

   API testing = verify correctness and error handling [OK]

Hint: Test APIs to check responses and errors before use [OK]

Common Mistakes:

• Thinking testing replaces coding
• Assuming APIs never change
• Believing testing improves server speed