Screenshot on failure in Selenium Python - Test Execution Trace

Test Overview

This test opens a webpage, tries to find a button, clicks it, and verifies the page title. If the test fails, it takes a screenshot to help diagnose the problem.

Test Code - unittest

Selenium Python

from selenium import webdriver
from selenium.webdriver.common.by import By
from selenium.common.exceptions import NoSuchElementException
import unittest

class TestScreenshotOnFailure(unittest.TestCase):
    def setUp(self):
        self.driver = webdriver.Chrome()
        self.driver.implicitly_wait(5)

    def test_click_button_and_check_title(self):
        driver = self.driver
        driver.get('https://example.com')
        try:
            button = driver.find_element(By.ID, 'submit-btn')
            button.click()
            self.assertEqual(driver.title, 'Expected Title')
        except Exception as e:
            driver.save_screenshot('failure_screenshot.png')
            raise e

    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 WebDriver Chrome browser opens	Chrome browser window is open and ready	—	PASS
2	Browser navigates to 'https://example.com'	Page 'https://example.com' is loaded in browser	—	PASS
3	Find element with ID 'submit-btn'	Button with ID 'submit-btn' is present on the page	—	PASS
4	Click the 'submit-btn' button	Button is clicked, page may change	—	PASS
5	Check if page title equals 'Expected Title'	Page title is checked	Assert page title == 'Expected Title'	PASS
6	Test ends and browser closes	Browser window is closed	—	PASS

Failure Scenario

Failing Condition: Element with ID 'submit-btn' is not found or page title is not 'Expected Title'

Execution Trace Quiz - 3 Questions

What happens if the button with ID 'submit-btn' is not found?

A The test passes without clicking the button

B The test ignores the missing button and continues

C A screenshot is taken and the test fails with NoSuchElementException

D The browser closes immediately without error

Key Result

Taking a screenshot immediately when a test fails helps quickly understand what the browser showed at failure time, making debugging easier.

Practice

1. What is the main purpose of taking a screenshot on test failure in Selenium?

easy

A. To capture the current state of the web page for debugging

B. To speed up the test execution

C. To improve the browser's performance

D. To automatically fix the test errors

Solution

1. Step 1: Understand the role of screenshots in testing

   Screenshots help testers see what the user saw when the test failed.

2. Step 2: Identify the purpose of capturing screenshots on failure

   They provide visual evidence to debug UI problems quickly.

3. Final Answer:

   To capture the current state of the web page for debugging -> Option A

4. Quick Check:

   Screenshot on failure = capture page state [OK]

Hint: Screenshots show what failed looks like visually [OK]

Common Mistakes:

• Thinking screenshots speed up tests
• Believing screenshots fix errors automatically
• Confusing screenshots with performance tools

2. Which of the following is the correct syntax to take a screenshot in Selenium Python when a test fails?

easy

A. driver.save_screenshot('error.png')

B. driver.takeScreenshot('error.png')

C. driver.capture('error.png')

D. driver.screenshotSave('error.png')

Solution

1. Step 1: Recall Selenium Python screenshot method

   The correct method to save a screenshot is save_screenshot().

2. Step 2: Verify method names and syntax

   Only driver.save_screenshot('error.png') matches Selenium's API.

3. Final Answer:

   driver.save_screenshot('error.png') -> Option A

4. Quick Check:

   Correct method name = save_screenshot [OK]

Hint: Remember method is save_screenshot with underscore [OK]

Common Mistakes:

• Using camelCase instead of snake_case
• Using non-existent methods like capture or screenshotSave
• Missing parentheses or quotes

3. What will be the output if the following Selenium Python code runs and the element is not found?

try:
    driver.find_element(By.ID, 'submit').click()
except Exception as e:
    driver.save_screenshot('fail.png')
    print('Screenshot saved on failure')

medium

A. No output, test passes silently

B. RuntimeError without screenshot

C. SyntaxError due to missing import

D. Screenshot saved on failure

Solution

1. Step 1: Analyze try-except behavior on element not found

   If element is missing, exception triggers except block.

2. Step 2: Check actions in except block

   Screenshot is saved and message printed: 'Screenshot saved on failure'.

3. Final Answer:

   Screenshot saved on failure -> Option D

4. Quick Check:

   Exception triggers screenshot and print [OK]

Hint: Exception triggers except block actions [OK]

Common Mistakes:

• Assuming test passes silently on failure
• Confusing syntax errors with runtime exceptions
• Ignoring the print statement inside except

4. Identify the error in this Selenium Python snippet intended to save a screenshot on failure:

try:
    driver.find_element(By.NAME, 'login').click()
except:
    driver.save_screenshot(failure.png)

medium

A. No error, code is correct

B. Incorrect exception handling syntax

C. Missing quotes around filename in save_screenshot

D. Wrong method name saveScreenshot instead of save_screenshot

Solution

1. Step 1: Check save_screenshot argument syntax

   Filename must be a string in quotes, but here it is unquoted.

2. Step 2: Confirm exception handling and method name

   Except syntax and method name are correct; only filename is wrong.

3. Final Answer:

   Missing quotes around filename in save_screenshot -> Option C

4. Quick Check:

   Filename must be a string in quotes [OK]

Hint: Always put filename in quotes for save_screenshot [OK]

Common Mistakes:

• Forgetting quotes around filename string
• Changing method name incorrectly
• Misusing except syntax

5. You want to automatically take a screenshot only when a Selenium test fails and save it with a timestamp. Which approach below correctly implements this in Python?

hard

A. Use driver.save_screenshot('fail.png') outside try-except block

B. Use try-except around test steps, call driver.save_screenshot(f"fail_{time.time()}.png") in except

C. Call driver.save_screenshot() before every test step unconditionally

D. Use a loop to retry test steps and save screenshot on success

Solution

1. Step 1: Understand when to take screenshots

   Screenshots should be taken only on failure, inside except block.

2. Step 2: Use timestamp for unique filenames

   Using time.time() in filename ensures unique screenshot names.

3. Final Answer:

   Use try-except around test steps, call driver.save_screenshot(f"fail_{time.time()}.png") in except -> Option B

4. Quick Check:

   Screenshot on failure with timestamp = try-except + formatted filename [OK]

Hint: Take screenshots only in except block with timestamped names [OK]

Common Mistakes:

• Taking screenshots before test steps always
• Saving screenshots outside exception handling
• Retrying tests without capturing failure screenshots