Request and response validation in Testing Fundamentals - Test Execution Trace

Test Overview

This test sends a request to a web API and checks if the response status and data are correct. It verifies that the server returns the expected success code and the right message in the response body.

Test Code - unittest

Testing Fundamentals

import requests
import unittest

class TestAPIRequestResponse(unittest.TestCase):
    def test_get_user(self):
        url = "https://api.example.com/user/123"
        response = requests.get(url)
        self.assertEqual(response.status_code, 200)
        data = response.json()
        self.assertIn('username', data)
        self.assertEqual(data['username'], 'john_doe')

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

Execution Trace - 6 Steps

Step	Action	System State	Assertion	Result
1	Test starts	Test runner initialized, ready to execute test_get_user	—	PASS
2	Sends GET request to https://api.example.com/user/123	HTTP request sent, waiting for response	—	PASS
3	Receives HTTP response with status code 200	Response received with JSON body {"username": "john_doe", "id": 123}	Check response.status_code == 200	PASS
4	Parses JSON response body	Parsed data contains keys: username, id	Check 'username' key exists in response JSON	PASS
5	Verifies username value is 'john_doe'	username value is 'john_doe'	Check data['username'] == 'john_doe'	PASS
6	Test ends successfully	All assertions passed, test case completed	—	PASS

Failure Scenario

Failing Condition: Response status code is not 200 or username key missing or username value incorrect

Execution Trace Quiz - 3 Questions

What does the test check first after sending the request?

A The HTTP status code is 200

B The username value is 'john_doe'

C The response time is less than 1 second

D The response contains an error message

Key Result

Always validate both the HTTP status code and the response data to ensure the API behaves as expected and returns correct information.

Practice

1. What is the main purpose of request and response validation in software testing?

easy

A. To write code faster

B. To check if the data sent and received matches expected formats and values

C. To design the user interface

D. To improve the speed of the application

Solution

1. Step 1: Understand the role of validation

   Request and response validation ensures the data sent and received is correct and follows expected rules.

2. Step 2: Identify the main goal

   This process helps catch errors early by verifying data formats and values before further processing.

3. Final Answer:

   To check if the data sent and received matches expected formats and values -> Option B

4. Quick Check:

   Validation = Check data correctness [OK]

Hint: Validation means checking data correctness both ways [OK]

Common Mistakes:

• Confusing validation with performance testing
• Thinking validation changes UI design
• Assuming validation speeds up coding

2. Which of the following is the correct way to assert that a response status code is 200 in a test script?

easy

A. assert response.code = 200

B. assert response.status == '200'

C. assert response.status_code = '200'

D. assert response.status_code == 200

Solution

1. Step 1: Check correct attribute and comparison

   The correct attribute for HTTP status code is status_code and it should be compared with == for equality.

2. Step 2: Identify correct syntax

   assert response.status_code == 200 uses assert response.status_code == 200, which is syntactically correct and logically valid.

3. Final Answer:

   assert response.status_code == 200 -> Option D

4. Quick Check:

   Use == to compare status_code with integer 200 [OK]

Hint: Use == to compare status_code with integer 200 [OK]

Common Mistakes:

• Using single = instead of == for comparison
• Comparing status_code to string '200' instead of integer
• Using wrong attribute names like status or code

3. Given this test code snippet:

response = api_call()
assert response.json()['success'] == True
assert response.status_code == 201

What will happen if the API returns status code 200 and success is True?

medium

A. Test will fail on the status code assertion

B. Test will pass successfully

C. Test will fail on the success key assertion

D. Test will raise a syntax error

Solution

1. Step 1: Check success key assertion

   The assertion response.json()['success'] == True will pass because success is True.

2. Step 2: Check status code assertion

   The assertion response.status_code == 201 will fail because the actual status code is 200, not 201.

3. Final Answer:

   Test will fail on the status code assertion -> Option A

4. Quick Check:

   Status code 200 != 201 causes failure [OK]

Hint: Check each assertion separately for pass/fail [OK]

Common Mistakes:

• Assuming test passes if one assertion passes
• Confusing status code 200 with 201
• Thinking syntax error occurs when assertions fail

4. You have this test code:

assert response.json()['data'] != None

But the test fails with a KeyError. What is the most likely cause?

medium

A. The 'data' key does not exist in the response JSON

B. The response is not JSON format

C. The assertion syntax is incorrect

D. The response status code is not 200

Solution

1. Step 1: Understand KeyError cause

   A KeyError happens when trying to access a dictionary key that does not exist.

2. Step 2: Analyze the assertion

   The assertion accesses response.json()['data']. If 'data' key is missing, KeyError occurs.

3. Final Answer:

   The 'data' key does not exist in the response JSON -> Option A

4. Quick Check:

   Missing key causes KeyError [OK]

Hint: KeyError means missing key in dictionary [OK]

Common Mistakes:

• Assuming assertion syntax error causes KeyError
• Thinking response format causes KeyError without checking keys
• Ignoring that missing keys cause KeyError

5. You want to validate a JSON response that may or may not include the key error. Which assertion correctly checks that if error exists, its value is a non-empty string?

hard

A. assert response.json()['error'] != ''

B. assert response.json().get('error') == ''

C. assert 'error' not in response.json() or (isinstance(response.json()['error'], str) and response.json()['error'] != '')

D. assert 'error' in response.json() and response.json()['error'] == ''

Solution

1. Step 1: Understand conditional validation

   The assertion must allow the 'error' key to be missing or, if present, check its value is a non-empty string.

2. Step 2: Analyze each option

   assert 'error' not in response.json() or (isinstance(response.json()['error'], str) and response.json()['error'] != '') uses logical OR: if 'error' not present, passes; else checks type and non-empty string. Other options fail if 'error' is missing or check wrong conditions.

3. Final Answer:

   assert 'error' not in response.json() or (isinstance(response.json()['error'], str) and response.json()['error'] != '') -> Option C

4. Quick Check:

   Allow missing key or validate non-empty string [OK]

Hint: Use OR to allow missing key or validate value [OK]

Common Mistakes:

• Assuming key always exists without checking
• Checking for empty string instead of non-empty
• Using incorrect logical operators