Headless mode for CI in Selenium Python - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to run Chrome in headless mode.

Selenium Python

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

options = Options()
options.add_argument([1])
driver = webdriver.Chrome(options=options)
driver.get('https://example.com')
driver.quit()

Drag options to blanks, or click blank then click option'

A"--start-maximized"

B"--incognito"

C"--headless"

D"--disable-extensions"

Attempts:

3 left

💡 Hint

Common Mistakes

Using options that don't enable headless mode like incognito or maximized window.

Forgetting to add the argument to options.

Adding the --headless argument runs Chrome without opening a visible window, which is perfect for CI environments.

2fill in blank

medium

Complete the code to set up Firefox in headless mode.

Selenium Python

from selenium import webdriver
from selenium.webdriver.firefox.options import Options

options = Options()
options.[1] = True
driver = webdriver.Firefox(options=options)
driver.get('https://example.com')
driver.quit()

Drag options to blanks, or click blank then click option'

Aincognito

Bheadless

Cmaximize_window

Ddisable_extensions

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect property names like incognito or maximize_window.

Setting the property to a string instead of a boolean.

Setting options.headless = True runs Firefox without opening a window, suitable for CI.

3fill in blank

hard

Fix the error in the code to correctly run Chrome headless in CI.

Selenium Python

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

options = Options()
options.add_argument([1])
driver = webdriver.Chrome(options=options)
driver.get('https://example.com')
driver.quit()

Drag options to blanks, or click blank then click option'

A"--headless"

B"--disable-gpu"

C"--no-sandbox"

D"--window-size=1920,1080"

Attempts:

3 left

💡 Hint

Common Mistakes

Not passing the options object to the Chrome driver constructor.

Using other arguments that don't enable headless mode.

The code misses passing options=options to webdriver.Chrome(). Adding --headless alone is not enough without using the options object.

4fill in blank

hard

Fill both blanks to create a headless Chrome driver with window size set for CI.

Selenium Python

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

options = Options()
options.add_argument([1])
options.add_argument([2])
driver = webdriver.Chrome(options=options)
driver.get('https://example.com')
driver.quit()

Drag options to blanks, or click blank then click option'

A"--headless"

B"--disable-gpu"

C"--window-size=1920,1080"

D"--incognito"

Attempts:

3 left

💡 Hint

Common Mistakes

Using --disable-gpu instead of window size for layout.

Forgetting to add both arguments.

Use --headless to run without GUI and --window-size=1920,1080 to set a standard window size in headless mode for consistent layout.

5fill in blank

hard

Fill all three blanks to create a Firefox headless driver with custom user agent and window size for CI.

Selenium Python

from selenium import webdriver
from selenium.webdriver.firefox.options import Options
from selenium.webdriver.firefox.firefox_profile import FirefoxProfile

options = Options()
options.[1] = True
profile = FirefoxProfile()
profile.set_preference('general.useragent.override', [2])
driver = webdriver.Firefox(options=options, firefox_profile=profile)
driver.set_window_size([3], 1080)
driver.get('https://example.com')
driver.quit()

Drag options to blanks, or click blank then click option'

Aheadless

B"Mozilla/5.0 (CI Testing)"

C1920

D"--headless"

Attempts:

3 left

💡 Hint

Common Mistakes

Using string "--headless" instead of boolean True for headless property.

Passing user agent without quotes or as a variable.

Setting window size width as a string instead of integer.

Set options.headless = True to run Firefox headless, override the user agent string with a custom value, and set the window width to 1920 pixels for consistent CI testing.

Practice

1. What is the main benefit of running Selenium tests in headless mode on a Continuous Integration (CI) server?

easy

A. Tests require manual interaction to proceed

B. Tests can only run on Windows operating systems

C. Tests run faster and use fewer resources because no browser window is displayed

D. Tests produce more detailed screenshots automatically

Solution

1. Step 1: Understand headless mode purpose

   Headless mode runs the browser without opening a visible window, saving system resources.

2. Step 2: Relate to CI environment needs

   CI servers often run tests automatically without user interaction, so headless mode speeds up tests and reduces resource use.

3. Final Answer:

   Tests run faster and use fewer resources because no browser window is displayed -> Option C

4. Quick Check:

   Headless mode = faster, resource-saving tests [OK]

Hint: Headless means no browser window, so tests run faster [OK]

Common Mistakes:

• Thinking headless mode requires manual input
• Believing headless mode only works on Windows
• Assuming headless mode automatically creates screenshots

2. Which of the following is the correct way to enable headless mode in Selenium with Python for Chrome?

easy

A. options = webdriver.ChromeOptions()
options.headless = True
browser = webdriver.Chrome(options=options)

B. options = webdriver.ChromeOptions()
options.add_argument('--headless')
browser = webdriver.Chrome(options=options)

C. browser = webdriver.Chrome()
browser.headless = True

D. browser = webdriver.Chrome()
browser.set_headless(True)

Solution

1. Step 1: Recall correct syntax for headless Chrome

   In Selenium Python, headless mode is enabled by adding the argument '--headless' to ChromeOptions.

2. Step 2: Check each option for correctness

   options = webdriver.ChromeOptions() options.add_argument('--headless') browser = webdriver.Chrome(options=options) correctly uses options.add_argument('--headless') and passes options to Chrome driver.

3. Final Answer:

   options = webdriver.ChromeOptions() options.add_argument('--headless') browser = webdriver.Chrome(options=options) -> Option B

4. Quick Check:

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

Hint: Use add_argument('--headless') on options for headless Chrome [OK]

Common Mistakes:

• Setting options.headless = True (not supported)
• Trying to set headless directly on browser instance
• Using non-existent set_headless method

3. What will be the output of the following Selenium Python code snippet when run on a CI server?

from selenium import webdriver
options = webdriver.FirefoxOptions()
options.add_argument('--headless')
driver = webdriver.Firefox(options=options)
driver.get('https://example.com')
title = driver.title
driver.quit()
print(title)

medium

A. Prints the page title 'Example Domain' without opening a browser window

B. Raises an error because Firefox does not support headless mode

C. Prints an empty string because headless mode disables page loading

D. Opens a visible browser window and prints the title

Solution

1. Step 1: Understand Firefox headless support

   Firefox supports headless mode via options.add_argument('--headless'), so the browser runs without UI.

2. Step 2: Analyze code behavior

   The code loads 'https://example.com', gets the page title 'Example Domain', then quits the driver and prints the title.

3. Final Answer:

   Prints the page title 'Example Domain' without opening a browser window -> Option A

4. Quick Check:

   Headless Firefox loads page and returns title correctly [OK]

Hint: Headless mode loads pages normally but hides browser window [OK]

Common Mistakes:

• Assuming headless disables page loading
• Thinking Firefox lacks headless support
• Expecting visible browser window in headless mode

4. You wrote this Selenium Python code to run Chrome in headless mode on a CI server, but tests fail with a timeout error:

options = webdriver.ChromeOptions()
options.add_argument('--headless')
driver = webdriver.Chrome(options=options)
driver.get('https://example.com')

What is the most likely cause and fix?

medium

A. The URL 'https://example.com' is invalid; use 'http://example.com'

B. Headless mode is not supported on Chrome; remove '--headless' argument

C. You must call driver.maximize_window() before get() in headless mode

D. Missing '--no-sandbox' argument; add options.add_argument('--no-sandbox') for CI environments

Solution

1. Step 1: Identify common CI environment issue

   On many CI servers, Chrome needs '--no-sandbox' to run properly in headless mode to avoid permission issues.

2. Step 2: Apply fix to options

   Add options.add_argument('--no-sandbox') along with '--headless' to fix timeout errors.

3. Final Answer:

   Missing '--no-sandbox' argument; add options.add_argument('--no-sandbox') for CI environments -> Option D

4. Quick Check:

   Use '--no-sandbox' with headless Chrome on CI [OK]

Hint: Add '--no-sandbox' for headless Chrome on CI to avoid timeouts [OK]

Common Mistakes:

• Removing headless argument thinking it's unsupported
• Calling maximize_window() unnecessarily in headless
• Changing URL without reason

5. You want to run Selenium tests in headless mode on a CI server using Chrome, but your tests intermittently fail because some elements are not interactable. Which combined approach best solves this problem?

hard

A. Enable headless mode with '--headless=new', add '--disable-gpu', and set a window size with options.add_argument('--window-size=1920,1080')

B. Use headless mode without window size and rely on default browser size

C. Disable headless mode and run tests with visible browser windows on CI

D. Add '--incognito' mode only without changing headless or window size

Solution

1. Step 1: Understand headless mode limitations

   Headless mode can cause layout differences; setting window size helps elements render correctly.

2. Step 2: Use modern headless flag and disable GPU

   Using '--headless=new' enables the latest headless mode in Chrome, and '--disable-gpu' avoids GPU issues in CI.

3. Step 3: Combine all options for stable tests

   Adding '--window-size=1920,1080' ensures consistent viewport, preventing element interaction failures.

4. Final Answer:

   Enable headless mode with '--headless=new', add '--disable-gpu', and set a window size with options.add_argument('--window-size=1920,1080') -> Option A

5. Quick Check:

   Use new headless, disable GPU, and set window size for stable CI tests [OK]

Hint: Set window size and use new headless mode for stable CI tests [OK]

Common Mistakes:

• Ignoring window size causing element not interactable errors
• Using old headless mode without '--headless=new'
• Disabling headless mode defeats CI automation purpose