Browser console log capture in Selenium Python - Test Execution Trace

Test Overview

This test opens a web page using Selenium in Python, captures the browser console logs, and verifies that there are no severe errors in the logs.

Test Code - unittest

Selenium Python

from selenium import webdriver
from selenium.webdriver.chrome.service import Service
from selenium.webdriver.common.by import By
from selenium.webdriver.chrome.options import Options
import unittest

class TestBrowserConsoleLog(unittest.TestCase):
    def setUp(self):
        chrome_options = Options()
        chrome_options.set_capability('goog:loggingPrefs', {'browser': 'ALL'})
        self.driver = webdriver.Chrome(service=Service(), options=chrome_options)

    def test_console_log_no_severe_errors(self):
        self.driver.get('https://example.com')
        logs = self.driver.get_log('browser')
        severe_errors = [entry for entry in logs if entry['level'] == 'SEVERE']
        self.assertEqual(len(severe_errors), 0, f"Found severe errors in console logs: {severe_errors}")

    def tearDown(self):
        self.driver.quit()

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

Execution Trace - 6 Steps

Step	Action	System State	Assertion	Result
1	Test starts and Chrome browser is launched with logging preferences set to capture browser console logs	Chrome browser window opens with logging enabled for browser console	—	PASS
2	Navigates to https://example.com	Browser displays the Example Domain webpage	—	PASS
3	Retrieves browser console logs using driver.get_log('browser')	Console logs are collected as a list of log entries	—	PASS
4	Filters logs to find entries with level 'SEVERE'	Filtered list contains only severe error log entries (empty if none found)	Check that the number of severe errors is zero	PASS
5	Assertion checks that no severe errors exist in console logs	Test verifies no severe errors in browser console	assertEqual(len(severe_errors), 0)	PASS
6	Browser is closed and test ends	Browser window closes, resources cleaned up	—	PASS

Failure Scenario

Failing Condition: There are one or more severe errors in the browser console logs

Execution Trace Quiz - 3 Questions

What does the test check in the browser console logs?

A That the browser window is maximized

B That the page title is correct

C That there are no severe errors

D That the page contains a specific element

Key Result

Capturing and checking browser console logs helps catch JavaScript errors early, improving test reliability and debugging.

Practice

1. What is the main purpose of capturing browser console logs in Selenium tests?

easy

A. To find hidden errors and warnings during test execution

B. To speed up the browser loading time

C. To change the browser's user interface

D. To increase the test execution timeout

Solution

1. Step 1: Understand browser console logs

   Browser console logs contain errors, warnings, and info messages from the browser during page load and interaction.

2. Step 2: Purpose of capturing logs in tests

   Capturing these logs helps testers find hidden errors or warnings that are not visible on the page but affect test results.

3. Final Answer:

   To find hidden errors and warnings during test execution -> Option A

4. Quick Check:

   Browser logs = find hidden errors [OK]

Hint: Browser logs reveal hidden errors during tests [OK]

Common Mistakes:

• Thinking logs speed up browser loading
• Confusing logs with UI changes
• Assuming logs affect timeout settings

2. Which of the following is the correct syntax to capture browser console logs in Selenium with Python?

easy

A. logs = driver.fetch_log('browser')

B. logs = driver.getLogs('console')

C. logs = driver.get_log('browser')

D. logs = driver.retrieve_log('console')

Solution

1. Step 1: Recall Selenium Python API for logs

   The correct method to get browser console logs is driver.get_log('browser').

2. Step 2: Check each option syntax

   Only logs = driver.get_log('browser') uses the exact correct method name and parameter. Others use incorrect method names or parameters.

3. Final Answer:

   logs = driver.get_log('browser') -> Option C

4. Quick Check:

   Correct method = get_log('browser') [OK]

Hint: Use driver.get_log('browser') to capture logs [OK]

Common Mistakes:

• Using incorrect method names like getLogs or fetch_log
• Passing wrong parameter like 'console' instead of 'browser'
• Confusing log capture with other driver methods

3. Given the following code snippet, what will be the output if the browser console has one error and one info message?

logs = driver.get_log('browser')
for entry in logs:
    print(entry['level'])

medium

A. []

B. ["INFO", "ERROR"]

C. ["WARNING", "ERROR"]

D. ["ERROR", "INFO"]

Solution

1. Step 1: Understand the code behavior

   The code fetches all browser logs and prints the 'level' field of each log entry in order.

2. Step 2: Analyze given log messages

   Since the console has one error and one info message, the output will list their levels in the order they appear: "ERROR" then "INFO".

3. Final Answer:

   ["ERROR", "INFO"] -> Option D

4. Quick Check:

   Print log levels = ["ERROR", "INFO"] [OK]

Hint: Print log['level'] to see message types in order [OK]

Common Mistakes:

• Assuming logs are sorted differently
• Confusing log levels with messages
• Expecting empty list if logs exist

4. Identify the error in this code snippet that tries to capture browser console logs:

logs = driver.get_log('console')
for log in logs:
    print(log['message'])

medium

A. Using 'log' as variable name causes conflict

B. Incorrect log type parameter; should be 'browser' instead of 'console'

C. Missing parentheses in print statement

D. No error; code is correct

Solution

1. Step 1: Check the parameter for get_log()

   The correct parameter to get browser console logs is 'browser', not 'console'.

2. Step 2: Verify other code parts

   Print statement syntax is correct, and variable name 'log' is valid. So no other errors.

3. Final Answer:

   Incorrect log type parameter; should be 'browser' instead of 'console' -> Option B

4. Quick Check:

   get_log parameter = 'browser' [OK]

Hint: Use 'browser' as parameter in get_log() [OK]

Common Mistakes:

• Using 'console' instead of 'browser' parameter
• Thinking print syntax is wrong in Python 3
• Worrying about variable names unnecessarily

5. You want to capture only error-level messages from the browser console logs in Selenium Python. Which code snippet correctly filters these logs?

hard

A. logs = [entry for entry in driver.get_log('browser') if entry['level'] == 'ERROR']

B. logs = driver.get_log('browser').filter(level='ERROR')

C. logs = driver.get_log('browser').select(entry => entry.level == 'ERROR')

D. logs = driver.get_log('browser').where(entry['level'] = 'ERROR')

Solution

1. Step 1: Understand filtering logs in Python

   Python list comprehension is used to filter logs by checking if entry['level'] equals 'ERROR'.

2. Step 2: Analyze each option's correctness

   logs = [entry for entry in driver.get_log('browser') if entry['level'] == 'ERROR'] uses valid Python syntax. Options A, B, and C use invalid or non-Python methods like filter(), select(), or where() which do not exist on lists.

3. Final Answer:

   logs = [entry for entry in driver.get_log('browser') if entry['level'] == 'ERROR'] -> Option A

4. Quick Check:

   Filter logs with list comprehension [OK]

Hint: Use list comprehension to filter logs by level [OK]

Common Mistakes:

• Using non-Python methods like filter or select on lists
• Using single equals '=' instead of '==' in conditions
• Trying to chain unsupported methods on get_log() result