Window size control in Selenium Python - Build an Automation Script

Verify browser window size can be set and retrieved

Preconditions (3)

Step 1: Open the browser using Selenium WebDriver

Step 2: Navigate to 'https://example.com'

Step 3: Set the browser window size to width 1024 and height 768

Step 4: Retrieve the current window size

Step 5: Verify that the window size width is 1024 and height is 768

Step 6: Close the browser

✅ Expected Result: The browser window size is set to 1024x768 and verified successfully before closing the browser

Automation Requirements - Selenium with Python

Assertions Needed:

Assert that the window width equals 1024

Assert that the window height equals 768

Best Practices:

Use explicit waits if needed before assertions

Use try-finally or context management to ensure browser closes

Use By locators only if interacting with page elements (not needed here)

Keep code readable and modular

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 TestWindowSize(unittest.TestCase):
    def setUp(self):
        options = Options()
        # options.add_argument('--headless')  # Uncomment to run headless
        self.driver = webdriver.Chrome(options=options)

    def test_window_size(self):
        driver = self.driver
        driver.get('https://example.com')

        # Set window size
        driver.set_window_size(1024, 768)

        # Get window size
        size = driver.get_window_size()

        # Assertions
        self.assertEqual(size['width'], 1024, f"Expected width 1024 but got {size['width']}")
        self.assertEqual(size['height'], 768, f"Expected height 768 but got {size['height']}")

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

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

This test uses Python's unittest framework with Selenium WebDriver.

setUp creates the browser instance before each test.

test_window_size navigates to example.com, sets the window size to 1024x768, then retrieves the size and asserts both width and height match the expected values.

tearDown closes the browser after the test to clean up.

This structure ensures the browser is always closed even if the test fails. Assertions include messages to help identify issues if the size is incorrect.

Common Mistakes - 4 Pitfalls

Not closing the browser after the test

Using hardcoded sleep instead of waiting for page load

Setting window size before navigating to a page

{'mistake': 'Using incorrect dictionary keys when retrieving window size', 'why_bad': 'Causes KeyError and test failure', 'correct_approach': "Use 'width' and 'height' keys exactly as returned by get_window_size()"}

Bonus Challenge

Now add data-driven testing with 3 different window sizes: (800x600), (1280x720), and (1920x1080)

Show Hint

Practice

1. What does the Selenium method set_window_size(width, height) do in a test script?

easy

A. It refreshes the current browser window.

B. It maximizes the browser window to full screen.

C. It changes the browser window size to the specified width and height.

D. It closes the browser window.

Solution

1. Step 1: Understand the method purpose

   The method set_window_size(width, height) is designed to set the browser window to a specific size.

2. Step 2: Compare with other window methods

   Maximizing, closing, or refreshing are done by different methods like maximize_window(), close(), or refresh().

3. Final Answer:

   It changes the browser window size to the specified width and height. -> Option C

4. Quick Check:

   set_window_size changes size [OK]

Hint: Remember: set_window_size sets exact width and height [OK]

Common Mistakes:

• Confusing set_window_size with maximize_window
• Thinking it closes or refreshes the window
• Using wrong method names

2. Which of the following is the correct syntax to set the browser window size to 1024x768 in Selenium Python?

easy

A. driver.set_window_size(1024, 768)

B. driver.setWindowSize(1024, 768)

C. driver.window_size(1024, 768)

D. driver.set_size(1024, 768)

Solution

1. Step 1: Identify correct method name and syntax

   The correct method in Selenium Python is set_window_size(width, height) with underscore and lowercase.

2. Step 2: Check method call format

   It is called on the driver object as driver.set_window_size(1024, 768).

3. Final Answer:

   driver.set_window_size(1024, 768) -> Option A

4. Quick Check:

   Correct method name and parameters [OK]

Hint: Use underscores and lowercase for Selenium Python methods [OK]

Common Mistakes:

• Using camelCase instead of snake_case
• Calling non-existent methods like set_size
• Missing driver object before method

3. What will be the output of the following code snippet?

driver.set_window_size(800, 600)
size = driver.get_window_size()
print(size)

medium

A. {'width': 800, 'height': 600}

B. {'width': 600, 'height': 800}

C. An error because get_window_size() does not exist

D. None

Solution

1. Step 1: Understand set_window_size effect

   The window size is set to width=800 and height=600.

2. Step 2: Check get_window_size output

   The method get_window_size() returns a dictionary with keys 'width' and 'height' reflecting the current window size.

3. Final Answer:

   {'width': 800, 'height': 600} -> Option A

4. Quick Check:

   get_window_size returns current size dict [OK]

Hint: get_window_size returns dict with width and height keys [OK]

Common Mistakes:

• Swapping width and height values
• Assuming get_window_size() does not exist
• Expecting a tuple instead of dict

4. Identify the error in this Selenium Python code snippet that tries to set the window size:

driver.set_window_size(1024)

medium

A. Method name should be setWindowSize, not set_window_size.

B. Missing the height parameter in set_window_size method.

C. The driver object is not defined.

D. set_window_size cannot be called directly on driver.

Solution

1. Step 1: Check method parameters

   The method set_window_size requires two parameters: width and height.

2. Step 2: Identify missing argument

   Only one argument (1024) is provided, so height is missing, causing a TypeError.

3. Final Answer:

   Missing the height parameter in set_window_size method. -> Option B

4. Quick Check:

   Two parameters required for set_window_size [OK]

Hint: Always provide both width and height to set_window_size [OK]

Common Mistakes:

• Providing only one parameter instead of two
• Using camelCase method name in Python
• Assuming driver is undefined without context

5. You want to test a website's responsive design by setting the browser window to three sizes: 320x480, 768x1024, and 1920x1080. Which code snippet correctly sets these sizes one after another with Selenium Python?

hard

A. sizes = [(320, 480), (768, 1024), (1920, 1080)]
for size in sizes:
driver.set_window_size(size)

B. sizes = [320, 480, 768, 1024, 1920, 1080]
for size in sizes:
driver.set_window_size(size)

C. driver.setWindowSize(320, 480)
driver.setWindowSize(768, 1024)
driver.setWindowSize(1920, 1080)

D. sizes = [(320, 480), (768, 1024), (1920, 1080)]
for w, h in sizes:
driver.set_window_size(w, h)

Solution

1. Step 1: Understand the sizes list format

   Sizes should be stored as tuples of (width, height) for easy unpacking.

2. Step 2: Use a for loop with unpacking

   Loop over sizes and unpack each tuple into width and height to call set_window_size(w, h).

3. Step 3: Eliminate incorrect options

   sizes = [320, 480, 768, 1024, 1920, 1080] for size in sizes: driver.set_window_size(size) uses a flat list and passes single integers (missing height parameter). driver.setWindowSize(320, 480) driver.setWindowSize(768, 1024) driver.setWindowSize(1920, 1080) uses camelCase setWindowSize (incorrect for Python Selenium). sizes = [(320, 480), (768, 1024), (1920, 1080)] for size in sizes: driver.set_window_size(size) loops but passes tuples directly (TypeError, expects two arguments).

4. Final Answer:

   sizes = [(320, 480), (768, 1024), (1920, 1080)] for w, h in sizes: driver.set_window_size(w, h) -> Option D

5. Quick Check:

   Use tuple unpacking for width and height [OK]

Hint: Use tuple unpacking in loop to set window sizes [OK]

Common Mistakes:

• Passing single integers instead of width and height pairs
• Calling set_window_size with a tuple instead of two arguments
• Using camelCase (setWindowSize) instead of snake_case