How To Handle Exceptions
Intro
It doesn't take long when using Selenium before you run into errors from Selenium that may seem inexplicable
(e.g., NoSuchElementError or StaleElementReferenceError). They can be a bit of a shock if you're not sure
what they are, how to handle them, or where to find documentation on how to address them.
A Solution
By adding some simple exception handling we can catch Selenium's errors and make our tests more resilient.
Let's take a look at an example.
Example
For this example we'll use a login example from the-internet.
Before each test we log in, and wait for the success message to be displayed (so we know the next page loaded). Then we want to check that the login form is no longer displayed.
The first test demonstrates the problem. If we look for the login form and ask if it's displayed, Selenium doesn't
answer false. It can't find the element at all (since it's not on the page anymore), so it throws a NoSuchElement
error.
The second test fixes it with a small helper that checks if an element is displayed and handles the exceptions:
NoSuchElement (the element is not on the page) and StaleElementReference (the element was on the page, but it
was removed or re-rendered). In both cases the element is not displayed, so the helper returns false. We're left
with a cleaner (and reusable) check for our tests.
NOTE: NoSuchElement and StaleElementReference are the two most common errors you'll run into when using
Selenium.
Expected Behavior
- Open the browser
- Log in and wait for the success message
- Check that looking for the login form throws an error (first test)
- Check that the login form is not displayed, with the helper (second test)
- Close the browser
Summary
Hopefully this tip has helped you handle the exceptions you'll run into when using Selenium.
Happy Testing!
Authors
