REST API testing basics in Testing Fundamentals - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the HTTP status code returned by this GET request?

Consider a REST API endpoint /users/123 that returns user details if the user exists. The user with ID 123 exists.

What HTTP status code should the server return for a successful GET request to /users/123?

A 404 Not Found

B 200 OK

C 500 Internal Server Error

D 201 Created

💡 Hint

Think about the standard response for a successful data retrieval.

A successful GET request returns 200 OK indicating the resource was found and returned.

❓ assertion

intermediate

Which assertion correctly verifies the JSON response contains the expected user name?

You receive this JSON response from a REST API:

{"id": 123, "name": "Alice", "email": "[e-mail]"}

Which assertion correctly checks that the name field is Alice?

A assert response.json()['name'] == 'Alice'

B assert response['name'] == 'Alice'

C assert response.json()['name'] = 'Alice'

D assert response.get('name') == 'Alice'

💡 Hint

Remember how to access JSON data from a response object.

Option A correctly calls response.json() to parse JSON and compares the name field. Option A and D are invalid because response is not a dict. Option A uses assignment = instead of comparison ==.

❓ locator

advanced

Which HTTP header is best to locate the API version in a request?

You want to test a REST API that supports multiple versions. Which HTTP header is the best practice to specify the API version in your request?

A Authorization

B Content-Type

C User-Agent

D Accept

💡 Hint

Think about which header tells the server what format or version the client expects.

The Accept header is used to specify the media type and version the client expects, e.g., application/vnd.api.v2+json. Content-Type describes the request body format, Authorization is for credentials, and User-Agent identifies the client software.

🔧 Debug

advanced

Why does this POST request test fail with a 400 Bad Request?

Test code sends this JSON payload in a POST request:

{"username": "bob", "password": 12345}

The API expects the password as a string, but the test fails with 400 Bad Request. Why?

A Password is sent as a number, but API expects a string

B Username field is missing

C POST method is not allowed on this endpoint

D JSON payload is missing required headers

💡 Hint

Check the data types in the JSON payload.

The API expects the password as a string, but the test sends it as a number (12345). This type mismatch causes the server to reject the request with 400 Bad Request.

❓ framework

expert

Which test framework feature best supports automated REST API testing with setup and teardown?

You want to write automated tests for REST APIs that require preparing test data before tests and cleaning up after. Which feature of a test framework best supports this?

A Parameterized tests

B Mocking HTTP requests

C Fixtures or setup/teardown methods

D Snapshot testing

💡 Hint

Think about how to prepare and clean test environments automatically.

Fixtures or setup/teardown methods allow you to prepare test data and environment before tests run and clean up after tests finish, which is essential for reliable REST API testing.

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