Network log capture in Selenium Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Selenium network log capture code?

Consider the following Python Selenium code snippet that captures network logs using Chrome DevTools Protocol (CDP). What will be printed by the last print statement?

Selenium Python

from selenium import webdriver
from selenium.webdriver.chrome.service import Service
from selenium.webdriver.chrome.options import Options
from selenium.webdriver.common.desired_capabilities import DesiredCapabilities

options = Options()
options.add_argument('--headless=new')

caps = DesiredCapabilities.CHROME.copy()
caps['goog:loggingPrefs'] = {'performance': 'ALL'}

service = Service()
driver = webdriver.Chrome(service=service, options=options, desired_capabilities=caps)

driver.get('https://example.com')

logs = driver.get_log('performance')

count = 0
for entry in logs:
    message = entry['message']
    if 'Network.responseReceived' in message:
        count += 1

print(count)
driver.quit()

A Raises a WebDriverException because DesiredCapabilities is deprecated

B Prints the number of network responses received during page load, typically a positive integer like 5 or more

C Raises a KeyError because 'message' key does not exist in log entries

D Prints 0 because 'performance' logs are not enabled by default

💡 Hint

Check how performance logging is enabled and what keys exist in the log entries.

The code enables performance logging via DesiredCapabilities and captures network events. Each log entry has a 'message' key containing JSON strings. Filtering for 'Network.responseReceived' counts network responses. This count is printed as a positive integer.

❓ assertion

intermediate

Which assertion correctly verifies a network request URL in Selenium logs?

You have captured performance logs in Selenium and want to assert that a request to 'https://api.example.com/data' was made. Which assertion code snippet correctly checks this?

Selenium Python

logs = driver.get_log('performance')
urls = []
for entry in logs:
    message = json.loads(entry['message'])['message']
    if message['method'] == 'Network.requestWillBeSent':
        urls.append(message['params']['request']['url'])

A assert any('https://api.example.com/data' in url for url in urls)

B assert 'https://api.example.com/data' in urls

C assert all('https://api.example.com/data' == url for url in urls)

D assert urls.index('https://api.example.com/data') > 0

💡 Hint

Check how to verify if at least one URL matches the target string.

Option A uses any() to check if the target URL is contained in any captured URL, which is correct. Option A checks exact membership which may fail if URLs have query parameters. Option A requires all URLs to match exactly, which is wrong. Option A raises ValueError if URL not found.

🔧 Debug

advanced

Why does this Selenium network log capture code raise a JSONDecodeError?

This code snippet tries to parse network logs but raises json.decoder.JSONDecodeError. Identify the cause.

Selenium Python

import json
logs = driver.get_log('performance')
for entry in logs:
    message = json.loads(entry['message'])
    print(message['message']['method'])

A entry['message'] is a string containing nested JSON; json.loads parses only the outer string, inner 'message' is still a string, causing error

B entry['message'] is not a valid JSON string, causing JSONDecodeError

C driver.get_log('performance') returns empty list, so loop never runs and error is elsewhere

D json module is not imported correctly, causing JSONDecodeError

💡 Hint

Check the structure of the 'message' field in performance logs.

The 'message' field is a JSON string that contains another JSON string inside the 'message' key. The code parses only once, so message['message'] is still a string, not a dict. Accessing ['method'] on a string causes JSONDecodeError or TypeError.

❓ framework

advanced

Which Selenium WebDriver setup correctly enables network log capture with Chrome in Python?

Select the code snippet that correctly configures Chrome WebDriver to capture network logs using performance logging.

A

from selenium import webdriver
from selenium.webdriver.chrome.service import Service

service = Service()
driver = webdriver.Chrome(service=service)
driver.execute_cdp_cmd('Network.enable', {})

B

from selenium import webdriver
from selenium.webdriver.chrome.options import Options

options = Options()
options.set_capability('goog:loggingPrefs', {'performance': 'ALL'})
options.add_argument('--headless')
driver = webdriver.Chrome(options=options)

C

from selenium import webdriver
from selenium.webdriver.chrome.service import Service
from selenium.webdriver.chrome.options import Options
from selenium.webdriver.common.desired_capabilities import DesiredCapabilities

caps = DesiredCapabilities.CHROME.copy()
caps['goog:loggingPrefs'] = {'performance': 'ALL'}

options = Options()
options.add_argument('--headless=new')

service = Service()
driver = webdriver.Chrome(service=service, options=options, desired_capabilities=caps)

D

from selenium import webdriver
from selenium.webdriver.chrome.options import Options

options = Options()
options.add_argument('--enable-logging')
driver = webdriver.Chrome(options=options)

💡 Hint

Check how to enable performance logging via DesiredCapabilities.

Option C correctly sets 'goog:loggingPrefs' in DesiredCapabilities and passes it to ChromeDriver. Option C tries to set capability on Options, which is invalid. Option C enables network via CDP but does not enable performance logs. Option C adds a logging argument but does not enable performance logs.

🧠 Conceptual

expert

What is the main limitation of capturing network logs via Selenium's performance logging?

Choose the most accurate statement about the limitations of using Selenium's performance logging to capture network traffic.

A Performance logging captures all network traffic including WebSocket frames and browser cache hits without any filtering limitations

B Performance logging disables browser caching, causing all resources to be fetched from the network every time

C Performance logging requires manual parsing of raw TCP packets, making it unsuitable for HTTP-level analysis

D Performance logging may miss some network events due to buffering and does not provide full HAR (HTTP Archive) data like dedicated proxy tools

💡 Hint

Consider what data Selenium's performance logs provide compared to specialized network tools.

Selenium's performance logging captures many network events but may miss some due to buffering and does not provide full HAR data. It does not capture raw TCP packets nor disables caching by default.