Browser console log capture in Selenium Python - Build an Automation Script

Capture and verify browser console logs on page load

Preconditions (3)

Step 1: Open the browser and navigate to 'https://example.com'

Step 2: Wait until the page is fully loaded

Step 3: Capture the browser console logs

Step 4: Check if there are any error messages in the console logs

✅ Expected Result: Browser console logs are captured successfully and no error messages are found

Automation Requirements - Selenium with Python

Assertions Needed:

Assert that console logs are not empty

Assert that no console log entry has level 'SEVERE' (error)

Best Practices:

Use explicit waits to ensure page load

Use appropriate log type 'browser' to capture console logs

Use try-except blocks to handle exceptions gracefully

Automated Solution

Selenium Python

from selenium import webdriver
from selenium.webdriver.chrome.service import Service
from selenium.webdriver.common.by import By
from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.support import expected_conditions as EC
from selenium.webdriver.chrome.options import Options
import unittest

class TestBrowserConsoleLogs(unittest.TestCase):
    def setUp(self):
        chrome_options = Options()
        chrome_options.set_capability('goog:loggingPrefs', {'browser': 'ALL'})
        self.driver = webdriver.Chrome(options=chrome_options)
        self.wait = WebDriverWait(self.driver, 10)

    def test_capture_console_logs(self):
        self.driver.get('https://example.com')
        # Wait for the page title to be present as indication of load
        self.wait.until(EC.title_contains('Example Domain'))

        logs = self.driver.get_log('browser')
        self.assertTrue(len(logs) > 0, 'Console logs should not be empty')

        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()

The setUp method configures Chrome to capture browser console logs by setting the goog:loggingPrefs capability.

The test navigates to https://example.com and waits explicitly for the page title to confirm the page loaded.

It then retrieves the browser console logs using get_log('browser').

Assertions check that logs are not empty and that no log entry has the level SEVERE, which indicates errors.

The tearDown method closes the browser to clean up.

This structure follows unittest framework conventions and uses explicit waits for reliability.

Common Mistakes - 4 Pitfalls

{'mistake': 'Not setting logging preferences in Chrome options', 'why_bad': 'Without setting logging preferences, browser console logs will not be captured.', 'correct_approach': "Set 'goog:loggingPrefs' capability with {'browser': 'ALL'} in Chrome options before creating the driver."}

Using implicit waits or no waits before capturing logs

{'mistake': 'Checking logs without filtering by log level', 'why_bad': 'Not filtering can cause false positives or miss critical errors.', 'correct_approach': "Filter logs by 'SEVERE' level to detect actual errors."}

{'mistake': 'Using incorrect log type name in get_log()', 'why_bad': "Using wrong log type (e.g., 'driver' instead of 'browser') returns empty or irrelevant logs.", 'correct_approach': "Use 'browser' as the log type to capture console logs."}

Bonus Challenge

Now add data-driven testing to capture console logs for these URLs: 'https://example.com', 'https://www.wikipedia.org', 'https://www.python.org'

Show Hint

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