REST API testing basics in Testing Fundamentals - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a REST API?

A REST API is a way for different software systems to talk to each other over the internet using simple rules like GET, POST, PUT, and DELETE.

beginner

Name the four main HTTP methods used in REST API testing.

GET (to read data), POST (to create data), PUT (to update data), DELETE (to remove data).

beginner

Why do we test REST APIs?

We test REST APIs to make sure they work correctly, return the right data, handle errors well, and perform fast enough.

beginner

What is a status code in REST API responses?

A status code is a number that tells if the API request worked or if there was a problem, like 200 means success, 404 means not found.

beginner

What is the difference between GET and POST methods?

GET asks for data without changing anything, while POST sends new data to the server to create something.

Which HTTP method is used to update existing data in REST API?

A PUT

B POST

C GET

D DELETE

PUT is used to update existing data on the server.

What does a 404 status code mean in REST API testing?

A Not Found

B Success

C Server Error

D Unauthorized

404 means the requested resource was not found on the server.

Which HTTP method should you use to retrieve data without changing it?

A POST

B PUT

C GET

D DELETE

GET is used to retrieve data without making changes.

Why is testing REST APIs important?

A To check if the user interface looks good

B To ensure the API works correctly and returns expected results

C To improve server hardware

D To write documentation

Testing ensures the API works correctly and returns the right data.

Which HTTP method is used to delete data in REST API?

A PUT

B POST

C GET

D DELETE

DELETE is used to remove data from the server.

Explain the main HTTP methods used in REST API testing and their purposes.

Think about what each method does to the data on the server.

Describe why status codes are important in REST API testing and give examples.

Status codes are like traffic lights for API responses.

Practice

1. What is the main purpose of REST API testing?

easy

A. To design the user interface of a web application

B. To write the backend code of the API

C. To check if the API correctly sends and receives data over the web

D. To create database tables for storing data

Solution

1. Step 1: Understand REST API testing goal

   REST API testing focuses on verifying communication between client and server using HTTP requests and responses.

2. Step 2: Identify the correct purpose

   Among the options, only checking data exchange over the web matches REST API testing.

3. Final Answer:

   To check if the API correctly sends and receives data over the web -> Option C

4. Quick Check:

   REST API testing = data exchange check [OK]

Hint: Remember: REST API testing checks data flow, not UI or code [OK]

Common Mistakes:

• Confusing API testing with UI design
• Thinking API testing means coding the API
• Mixing API testing with database design

2. Which HTTP method is commonly used to retrieve data from a REST API?

easy

A. POST

B. GET

C. DELETE

D. PUT

Solution

1. Step 1: Recall HTTP methods and their uses

   GET is used to request data, POST to send data, DELETE to remove data, and PUT to update data.

2. Step 2: Match method to retrieving data

   Retrieving data means reading it without changing, which is the GET method.

3. Final Answer:

   GET -> Option B

4. Quick Check:

   Retrieve data = GET method [OK]

Hint: GET means get data; POST means send data [OK]

Common Mistakes:

• Choosing POST instead of GET for data retrieval
• Confusing PUT with GET
• Using DELETE to get data

3. Given this response from a REST API test:
{"status":200, "body": {"name": "Alice", "age": 30}}
What does the status code 200 mean?

medium

A. The request was successful and data is returned

B. The requested resource was not found

C. There was a server error processing the request

D. The request was unauthorized

Solution

1. Step 1: Understand HTTP status codes

   Status code 200 means OK, indicating success. 404 means not found, 500 means server error, 401 means unauthorized.

2. Step 2: Match code 200 to meaning

   Since the response shows 200, it means the request succeeded and data is returned.

3. Final Answer:

   The request was successful and data is returned -> Option A

4. Quick Check:

   Status 200 = success [OK]

Hint: 200 means success; 404 means missing; 500 means error [OK]

Common Mistakes:

• Confusing 200 with error codes
• Thinking 200 means unauthorized
• Ignoring the status code meaning

4. You wrote this test code to check a REST API response status:

response = send_request('GET', '/users/1')
assert response.status_code = 200

What is the error in this code?

medium

A. Incorrect HTTP method used

B. Using single quotes instead of double quotes in the URL

C. Missing parentheses in the send_request function call

D. Using '=' instead of '==' in the assertion

Solution

1. Step 1: Check assertion syntax

   In Python, '=' is for assignment, '==' is for comparison. Assertions need '==' to compare values.

2. Step 2: Identify the error in the assertion line

   The code uses '=' which causes a syntax error. It should be '==' to check if status_code equals 200.

3. Final Answer:

   Using '=' instead of '==' in the assertion -> Option D

4. Quick Check:

   Assertion needs '==' not '=' [OK]

Hint: Use '==' to compare values in assertions, not '=' [OK]

Common Mistakes:

• Confusing assignment '=' with comparison '=='
• Ignoring syntax errors in assertions
• Assuming single quotes cause error here

5. You want to test a REST API endpoint that returns a list of users. Which test case best checks if the API handles an empty user list correctly?

hard

A. Send a GET request and verify the response body is an empty list and status code is 200

B. Send a POST request with user data and check for status code 201

C. Send a DELETE request to remove all users and expect status code 404

D. Send a GET request and expect status code 500 when no users exist

Solution

1. Step 1: Understand the test goal for empty user list

   The API should return an empty list with a success status (200) when no users exist.

2. Step 2: Evaluate each option for correctness

   Send a GET request and verify the response body is an empty list and status code is 200 correctly sends GET and expects empty list and 200. Send a POST request with user data and check for status code 201 is about creating users, not testing empty list. Send a DELETE request to remove all users and expect status code 404 expects 404 after deletion, which is incorrect for empty list response. Send a GET request and expect status code 500 when no users exist expects 500 error, which is wrong for empty data.

3. Final Answer:

   Send a GET request and verify the response body is an empty list and status code is 200 -> Option A

4. Quick Check:

   Empty list test = GET + empty list + 200 [OK]

Hint: Empty data should return 200 with empty list, not error [OK]

Common Mistakes:

• Expecting error codes for empty data
• Using wrong HTTP methods for retrieval
• Confusing creation or deletion tests with retrieval