Stop 06 · Programming Fundamentals for AutomationTopics · 5/10

Exception Handling

In short

One missing button shouldn't crash your whole night's test run. Exception handling lets a script fail politely: record what broke, clean up, and keep going.

Gracefully handling errors in a test script (like an element not being found) rather than letting the entire test suite crash on the first failure — essential for a stable, informative automation suite.

The purple blob keeps working on a laptop under a glowing bulb while an inverter box glows on the floor.

Think of it like this

The inverter during a power cut

Light goes off mid-study. You don't panic and abandon the exam prep. The inverter kicks in, the fan keeps spinning, and you note 'power cut at 9 pm' for the society WhatsApp group. try/except is your script's inverter.

Watch it happen

A failed click, handled well

Test script

Web page

Report

find #pay-button

1/5The script tries to find the Pay button inside a try block.

The big ideas

What you need to know

try wraps risk

Put the line that might fail inside try. If it fails, Python jumps to except.

Catch specific errors

Catch TimeoutException, not every exception. Catching everything hides real bugs.

finally cleans up

Close browsers, delete temp files, log out. finally runs no matter what happened.

Don't swallow failures

A caught error must still fail the test, or your report shows green over broken code.

See it in code

Walk through the code

python

1from selenium import webdriver2from selenium.webdriver.common.by import By3from selenium.common.exceptions import NoSuchElementException4 5driver = webdriver.Chrome()6try:7    driver.get("https://www.saucedemo.com/")8    driver.find_element(By.ID, "pay-button").click()9except NoSuchElementException:10    driver.save_screenshot("pay_button_missing.png")11    raise12finally:13    driver.quit()

1/4The risky steps go inside try. pay-button doesn't exist on this page, so line 8 fails.

Catch, collect evidence, re-raise so the test still fails, and always close the browser.

Save yourself the pain

Common mistakes

Oops

Writing except: pass to make red tests go away.

Do this instead

Catch a specific exception, log it, and re-raise or fail the test clearly.

Oops

Closing the browser only at the end of the happy path.

Do this instead

Put cleanup in finally, or in your framework's teardown, so it runs after failures too.

Your mission

Handle a bad file name

~20 min

Quick check

Why re-raise an exception after taking a screenshot in a test?

Go deeper

1Add try/catch (or try/except) error handling to a script and test it against a failure scenario.
2Learn why swallowing exceptions silently hides real problems from your test reports.
3Practice writing an error message that clearly explains what went wrong when a test fails.