Why API testing validates backend logic in Testing Fundamentals - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to send a GET request to the API endpoint.

Testing Fundamentals

response = requests.[1]('https://api.example.com/data')

Drag options to blanks, or click blank then click option'

Aget

Bpost

Cput

Ddelete

Attempts:

3 left

💡 Hint

Common Mistakes

Using POST instead of GET to retrieve data.

The GET method is used to retrieve data from the API, which is essential for validating backend logic.

2fill in blank

medium

Complete the code to check if the API response status code is 200 (OK).

Testing Fundamentals

assert response.[1] == 200

Drag options to blanks, or click blank then click option'

Atext

Bstatus_code

Cjson

Dheaders

Attempts:

3 left

💡 Hint

Common Mistakes

Checking response.text instead of response.status_code.

The status_code attribute holds the HTTP status code returned by the API, which indicates success or failure.

3fill in blank

hard

Fix the error in the assertion that checks if the 'success' field in JSON response is True.

Testing Fundamentals

assert response.json()[[1]] == True

Drag options to blanks, or click blank then click option'

A'Success'

Bsuccess

C'success'

D'status'

Attempts:

3 left

💡 Hint

Common Mistakes

Using unquoted key causing a NameError.

The key must be a string matching exactly the JSON field name, so it needs quotes around 'success'.

4fill in blank

hard

Fill both blanks to extract the 'user_id' from JSON response and check if it equals 123.

Testing Fundamentals

user_id = response.json().[1]('user_id')
assert user_id [2] 123

Drag options to blanks, or click blank then click option'

Aget

B==

C=

D!=

Attempts:

3 left

💡 Hint

Common Mistakes

Using assignment '=' instead of comparison '==' in assertion.

Use get to safely access 'user_id' and == to compare values.

5fill in blank

hard

Fill all three blanks to send a POST request with JSON data and check if response status is 201.

Testing Fundamentals

payload = {'name': 'Alice', 'age': 30}
response = requests.[1]('https://api.example.com/users', json=[2])
assert response.[3] == 201

Drag options to blanks, or click blank then click option'

Apost

Bpayload

Cstatus_code

Dget

Attempts:

3 left

💡 Hint

Common Mistakes

Using GET instead of POST for sending data.

Checking wrong attribute for status code.

Use post to send data, pass payload as JSON, and check status_code for 201 Created.

Practice

1. Why is API testing important for validating backend logic?

easy

A. Because it checks the server's response and business rules directly

B. Because it tests the colors and layout of the user interface

C. Because it only tests the database without any requests

D. Because it focuses on hardware performance

Solution

1. Step 1: Understand what API testing does and compare options

   API testing sends requests to the backend and checks the responses to verify logic and data handling. Only "Because it checks the server's response and business rules directly" correctly states that API testing checks server responses and business rules directly.

2. Final Answer:

   Because it checks the server's response and business rules directly -> Option A

3. Quick Check:

   API testing validates backend logic = Because it checks server response [OK]

Hint: API testing checks backend responses, not UI or hardware [OK]

Common Mistakes:

• Confusing API testing with UI testing
• Thinking API tests hardware or database only
• Assuming API testing is only about data storage

2. Which of the following is the correct way to send a GET request in an API test using JavaScript fetch?

easy

A. fetch('https://api.example.com/data', { method: 'DELETE' })

B. fetch('https://api.example.com/data', { method: 'POST' })

C. fetch('https://api.example.com/data', { method: 'GET' })

D. fetch('https://api.example.com/data', { method: 'PUT' })

Solution

1. Step 1: Identify the HTTP method for GET request and match in fetch options

   The GET method is used to retrieve data from the server. fetch('https://api.example.com/data', { method: 'GET' }) uses method: 'GET', which is correct for fetching data.

2. Final Answer:

   fetch('https://api.example.com/data', { method: 'GET' }) -> Option C

3. Quick Check:

   GET request uses method 'GET' in fetch [OK]

Hint: GET requests use method 'GET' in fetch options [OK]

Common Mistakes:

• Using POST or other methods instead of GET for data retrieval
• Omitting the method option (defaults to GET but unclear)
• Confusing HTTP methods in fetch

3. Consider this Python code snippet for API testing using requests library:

response = requests.post('https://api.example.com/login', json={'user':'test', 'pass':'1234'})
print(response.status_code)

What will be the output if the login is successful?

medium

A. 200

B. 404

C. 500

D. 401

Solution

1. Step 1: Understand HTTP status codes for API responses and match with success

   A successful POST request usually returns status code 200 (OK) or 201 (Created). Here, 200 is expected for successful login. Options 404 (Not Found), 500 (Server Error), and 401 (Unauthorized) indicate failure or errors.

2. Final Answer:

   200 -> Option A

3. Quick Check:

   Successful API call returns 200 status code [OK]

Hint: Success status code is 200 in API responses [OK]

Common Mistakes:

• Confusing 401 Unauthorized with success
• Thinking 404 means success
• Assuming 500 means success

4. You wrote this API test code snippet in JavaScript:

const response = await fetch('https://api.example.com/items', { method: 'GET' });
const data = await response.json();
console.log(data.items.length);

But the test fails with error: TypeError: Cannot read property 'length' of undefined. What is the likely cause?

medium

A. The URL is missing a trailing slash

B. The fetch method should be 'POST' instead of 'GET'

C. The await keyword is used incorrectly

D. The response JSON does not have an 'items' property

Solution

1. Step 1: Analyze the error message and check response structure

   The error says 'length' of undefined, meaning data.items is undefined. If the JSON response lacks 'items', accessing data.items.length causes this error.

2. Final Answer:

   The response JSON does not have an 'items' property -> Option D

3. Quick Check:

   Undefined property causes length error [OK]

Hint: Check if JSON property exists before accessing length [OK]

Common Mistakes:

• Changing HTTP method unnecessarily
• Misusing await keyword
• Assuming URL format causes this error

5. You want to test a backend API that calculates discounts based on user type and purchase amount. Which API testing approach best validates the backend logic?

hard

A. Test only the frontend UI to see if discount shows correctly

B. Send requests with different user types and amounts, then verify the discount in the response

C. Check the database directly without sending API requests

D. Run performance tests to measure response time only

Solution

1. Step 1: Identify what validates backend logic and compare options

   Sending requests with varied inputs and checking responses tests the business rules implemented in backend. "Send requests with different user types and amounts, then verify the discount in the response" sends inputs and verifies outputs, directly testing backend logic. Other options miss backend logic validation.

2. Final Answer:

   Send requests with different user types and amounts, then verify the discount in the response -> Option B

3. Quick Check:

   API tests validate logic by input-output checks [OK]

Hint: Test backend logic by varying inputs and checking outputs [OK]

Common Mistakes:

• Testing only UI without backend verification
• Skipping API requests and checking database only
• Focusing on performance instead of logic correctness