API test automation concepts in Testing Fundamentals - Test Execution Trace

Test Overview

This test sends a GET request to a sample API endpoint and verifies the response status code and content. It checks that the API returns the expected data, ensuring the API works correctly.

Test Code - unittest

Testing Fundamentals

import requests
import unittest

class TestSampleAPI(unittest.TestCase):
    def test_get_user(self):
        url = "https://jsonplaceholder.typicode.com/users/1"
        response = requests.get(url)
        self.assertEqual(response.status_code, 200)
        data = response.json()
        self.assertEqual(data["id"], 1)
        self.assertIn("username", data)

if __name__ == "__main__":
    unittest.main()

Execution Trace - 6 Steps

Step	Action	System State	Assertion	Result
1	Test starts	Test runner initializes the test class and method	—	PASS
2	Sends GET request to https://jsonplaceholder.typicode.com/users/1	HTTP request sent to API server	—	PASS
3	Receives HTTP response from API	Response object contains status code and JSON data	Check response.status_code == 200	PASS
4	Parses JSON response body	JSON data loaded into a dictionary	Check data["id"] == 1	PASS
5	Verifies 'username' key exists in response data	Response JSON contains expected fields	Check 'username' in data	PASS
6	Test ends successfully	All assertions passed, test completes	—	PASS

Failure Scenario

Failing Condition: API returns a status code other than 200 or missing expected data fields

Execution Trace Quiz - 3 Questions

What does the test verify first after sending the GET request?

A The response time is less than 1 second

B The HTTP status code is 200

C The response contains a 'username' field

D The API endpoint URL is correct

Key Result

Always verify both the HTTP status code and the response content to ensure the API behaves as expected.

Practice

1. What is the main purpose of API test automation?

easy

A. To design the user interface of an application

B. To check if different software parts communicate correctly

C. To write code for the backend server

D. To create database schemas

Solution

1. Step 1: Understand API test automation goal

   API test automation focuses on verifying communication between software parts via APIs.

2. Step 2: Eliminate unrelated options

   Designing UI, writing backend code, and creating database schemas are not related to API test automation.

3. Final Answer:

   To check if different software parts communicate correctly -> Option B

4. Quick Check:

   API test automation = communication check [OK]

Hint: API tests check communication, not UI or database [OK]

Common Mistakes:

• Confusing API testing with UI testing
• Thinking API tests create backend code
• Mixing API testing with database design

2. Which of the following is the correct way to check the HTTP status code in an automated API test using Python's requests library?

easy

A. response.code == 200

B. response.status == 200

C. response.status_code == 200

D. response.statusCode == 200

Solution

1. Step 1: Recall Python requests response attribute

   The correct attribute to get HTTP status code is status_code.

2. Step 2: Match options with correct attribute

   Only response.status_code == 200 uses the correct attribute and syntax.

3. Final Answer:

   response.status_code == 200 -> Option C

4. Quick Check:

   requests status code = status_code [OK]

Hint: Use response.status_code to check HTTP status in Python [OK]

Common Mistakes:

• Using incorrect attribute names like status or code
• Confusing camelCase with snake_case
• Forgetting double equals for comparison

3. Given this Python code snippet for an API test:

import requests
response = requests.get('https://api.example.com/data')
print(response.json()['status'])

What will be the output if the API response JSON is {"status": "success", "data": []}?

medium

A. "success"

B. KeyError

C. {'status': 'success'}

D. success

Solution

1. Step 1: Understand response.json() output

   response.json() returns a Python dictionary parsed from JSON.

2. Step 2: Access the 'status' key value

   Accessing ['status'] returns the string "success" without quotes in print output.

3. Final Answer:

   success -> Option D

4. Quick Check:

   Print dict value = string without quotes [OK]

Hint: Print of string value shows without quotes in Python [OK]

Common Mistakes:

• Expecting quotes around printed string
• Confusing JSON string with Python print output
• Assuming KeyError without checking keys

4. You wrote this API test code snippet:

response = requests.post('https://api.example.com/login', data={'user': 'admin', 'pass': '1234'})
assert response.status_code = 200

What is the error and how to fix it?

medium

A. Use '==' for comparison in assert, not '='

B. Change 'data' to 'json' in requests.post() call

C. Use 'response.status' instead of 'response.status_code'

D. Add parentheses around assert condition

Solution

1. Step 1: Identify syntax error in assert statement

   The assert statement uses '=' which is assignment, not comparison.

2. Step 2: Correct assert syntax

   Replace '=' with '==' to compare response.status_code to 200.

3. Final Answer:

   Use '==' for comparison in assert, not '=' -> Option A

4. Quick Check:

   Assert needs '==' for comparison [OK]

Hint: Assert uses '==' to compare, '=' assigns [OK]

Common Mistakes:

• Using '=' instead of '==' in assert
• Confusing 'data' and 'json' parameters (not error here)
• Using wrong attribute like response.status

5. You want to automate testing an API that returns a list of users with their ages. You need to verify the API only returns users aged 18 or older. Which approach best fits this requirement?

hard

A. Send a GET request, parse JSON response, then assert all ages >= 18

B. Send a POST request with age filter, then check status code 200

C. Check only the first user's age in the response

D. Verify the response content type is 'text/html'

Solution

1. Step 1: Understand requirement to verify all users' ages

   We must check every user's age is 18 or older in the response data.

2. Step 2: Choose approach that parses response and asserts condition on all users

   Sending GET, parsing JSON, and asserting all ages >= 18 matches the need.

3. Final Answer:

   Send a GET request, parse JSON response, then assert all ages >= 18 -> Option A

4. Quick Check:

   Check all data items for condition [OK]

Hint: Check all items, not just one, for correct data [OK]

Common Mistakes:

• Checking only first user age
• Using wrong HTTP method for retrieval
• Verifying wrong response content type