Browser options and capabilities in Selenium Python - Build an Automation Script

Set Chrome browser options and verify window size

Preconditions (2)

Step 1: Create a ChromeOptions object

Step 2: Set the browser window size to 1024x768 using ChromeOptions

Step 3: Start Chrome browser with these options

Step 4: Navigate to https://www.example.com

Step 5: Verify that the browser window size is 1024x768

✅ Expected Result: The Chrome browser opens with window size 1024x768 and loads https://www.example.com successfully

Automation Requirements - Selenium with Python

Assertions Needed:

Verify browser window size is 1024x768 after browser launch

Verify page title contains 'Example Domain' after navigation

Best Practices:

Use ChromeOptions to set browser capabilities

Use explicit waits if needed

Use assertions from unittest or pytest

Close the browser after test

Automated Solution

Selenium Python

from selenium import webdriver
from selenium.webdriver.chrome.service import Service
from selenium.webdriver.chrome.options import Options
import unittest

class TestChromeOptions(unittest.TestCase):
    def setUp(self):
        chrome_options = Options()
        chrome_options.add_argument('--window-size=1024,768')
        self.driver = webdriver.Chrome(options=chrome_options)

    def test_window_size_and_navigation(self):
        self.driver.get('https://www.example.com')
        width = self.driver.execute_script('return window.innerWidth')
        height = self.driver.execute_script('return window.innerHeight')
        self.assertEqual(width, 1024, 'Window width should be 1024')
        self.assertEqual(height, 768, 'Window height should be 768')
        self.assertIn('Example Domain', self.driver.title, 'Page title should contain Example Domain')

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

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

This test uses ChromeOptions to set the browser window size before launching Chrome. The --window-size=1024,768 argument sets the window size. After launching, the test navigates to https://www.example.com. It then uses JavaScript to get the actual window inner width and height and asserts they match the expected size. It also checks the page title to confirm navigation succeeded. The test uses Python's unittest framework for structure and assertions. The tearDown method ensures the browser closes after the test to keep the environment clean.

Common Mistakes - 3 Pitfalls

Setting window size after browser launch instead of using ChromeOptions

Using hardcoded sleep instead of checking window size dynamically

Not closing the browser after test

Bonus Challenge

Now add data-driven testing to launch Chrome with three different window sizes: 800x600, 1280x720, and 1920x1080, verifying each size.

Show Hint

Practice

1. What is the main purpose of using Options in Selenium WebDriver for browsers?

easy

A. To customize browser settings like headless mode or window size

B. To write test assertions for page elements

C. To locate elements on a web page

D. To generate test reports automatically

Solution

1. Step 1: Understand what Options configure

   Options allow you to set how the browser behaves during tests, such as running headless or setting window size.

2. Step 2: Differentiate Options from other tasks

   Options do not handle locating elements, assertions, or reports; those are separate tasks.

3. Final Answer:

   To customize browser settings like headless mode or window size -> Option A

4. Quick Check:

   Options = Browser customization [OK]

Hint: Options control browser behavior, not test logic [OK]

Common Mistakes:

• Confusing Options with element locators
• Thinking Options generate reports
• Mixing Options with assertion logic

2. Which of the following is the correct way to set Chrome to run in headless mode using Selenium in Python?

easy

A. options = webdriver.ChromeOptions()
options.add_argument('--headless')

B. options = webdriver.ChromeOptions()
options.set_headless(True)

C. options = webdriver.ChromeOptions()
options.headless = True

D. options = webdriver.ChromeOptions()
options.add_option('headless')

Solution

1. Step 1: Recall correct method to add arguments

   In Selenium Python, add_argument is used to add command line switches like '--headless'.

2. Step 2: Check each option's syntax

   Only options = webdriver.ChromeOptions() options.add_argument('--headless') uses add_argument('--headless') correctly; others use invalid or non-existent methods.

3. Final Answer:

   options = webdriver.ChromeOptions() options.add_argument('--headless') -> Option A

4. Quick Check:

   Use add_argument('--headless') for headless mode [OK]

Hint: Use add_argument('--headless') to enable headless mode [OK]

Common Mistakes:

• Using non-existent set_headless method
• Assigning headless attribute directly
• Using add_option instead of add_argument

3. What will be the effect of the following Python Selenium code snippet?

from selenium import webdriver
options = webdriver.FirefoxOptions()
options.set_preference('dom.webnotifications.enabled', False)
driver = webdriver.Firefox(options=options)
driver.get('https://example.com')

medium

A. Code will raise an error due to invalid method

B. Firefox will launch but notifications will still appear

C. Firefox will launch with notifications disabled on the page

D. Firefox will launch in headless mode

Solution

1. Step 1: Understand set_preference usage

   The method set_preference sets Firefox preferences; here it disables web notifications.

2. Step 2: Analyze the effect on browser behavior

   Passing these options to Firefox disables notifications on pages, so no pop-ups appear.

3. Final Answer:

   Firefox will launch with notifications disabled on the page -> Option C

4. Quick Check:

   set_preference disables notifications [OK]

Hint: set_preference disables features like notifications [OK]

Common Mistakes:

• Assuming notifications still appear
• Confusing set_preference with add_argument
• Thinking code runs headless by default

4. Identify the error in this Selenium Python code snippet that tries to disable browser notifications in Chrome:

from selenium import webdriver
options = webdriver.ChromeOptions()
options.set_preference('profile.default_content_setting_values.notifications', 2)
driver = webdriver.Chrome(options=options)

medium

A. The value 2 is invalid for disabling notifications

B. set_preference is not a method of ChromeOptions

C. Options must be passed as capabilities, not options

D. ChromeOptions cannot disable notifications

Solution

1. Step 1: Check ChromeOptions methods

   ChromeOptions does not have a method called set_preference; this is Firefox-specific.

2. Step 2: Correct way to disable notifications in Chrome

   Chrome uses add_experimental_option with 'prefs' dictionary to disable notifications.

3. Final Answer:

   set_preference is not a method of ChromeOptions -> Option B

4. Quick Check:

   Use add_experimental_option for Chrome prefs [OK]

Hint: ChromeOptions uses add_experimental_option, not set_preference [OK]

Common Mistakes:

• Using Firefox methods on ChromeOptions
• Passing wrong values for notification settings
• Confusing options with capabilities

5. You want to run Chrome in headless mode, disable notifications, and accept insecure certificates using Selenium in Python. Which code snippet correctly sets all these options?

hard

A. options = webdriver.ChromeOptions()
options.headless = True
options.add_experimental_option('prefs', {'notifications': 0})
options.set_capability('acceptInsecureCerts', False)
driver = webdriver.Chrome(options=options)

B. options = webdriver.ChromeOptions()
options.add_argument('headless')
options.set_preference('notifications', False)
options.set_capability('acceptInsecureCerts', True)
driver = webdriver.Chrome(options=options)

C. options = webdriver.ChromeOptions()
options.add_argument('--headless')
options.add_argument('--disable-notifications')
options.accept_insecure_certs = True
driver = webdriver.Chrome(options=options)

D. options = webdriver.ChromeOptions()
options.add_argument('--headless')
options.add_experimental_option('prefs', {'profile.default_content_setting_values.notifications': 2})
options.set_capability('acceptInsecureCerts', True)
driver = webdriver.Chrome(options=options)

Solution

1. Step 1: Set headless mode correctly

   Use add_argument('--headless') to enable headless mode in ChromeOptions.

2. Step 2: Disable notifications properly

   Use add_experimental_option('prefs', {'profile.default_content_setting_values.notifications': 2}) to disable notifications.

3. Step 3: Accept insecure certificates

   Set capability acceptInsecureCerts to True using set_capability.

4. Final Answer:

   options = webdriver.ChromeOptions() options.add_argument('--headless') options.add_experimental_option('prefs', {'profile.default_content_setting_values.notifications': 2}) options.set_capability('acceptInsecureCerts', True) driver = webdriver.Chrome(options=options) -> Option D

5. Quick Check:

   Combine add_argument, add_experimental_option, set_capability [OK]

Hint: Use add_argument, add_experimental_option, set_capability together [OK]

Common Mistakes:

• Missing '--' in headless argument
• Using set_preference on ChromeOptions
• Setting acceptInsecureCerts to False by mistake