Custom expected conditions in Selenium Python - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a custom expected condition in Selenium?

A custom expected condition is a user-defined function or class that waits for a specific condition to be true before proceeding, extending Selenium's built-in wait capabilities.

beginner

Why use custom expected conditions instead of built-in ones?

Custom expected conditions allow you to wait for unique or complex scenarios that built-in conditions do not cover, making tests more reliable and tailored to your app.

intermediate

How do you create a custom expected condition using a class in Selenium Python?

Create a class with a __call__ method that takes a driver and returns a truthy value when the condition is met or False otherwise. This class can then be used with WebDriverWait.

beginner

What should a custom expected condition return when the condition is not met?

It should return False or None to indicate the wait should continue until the timeout or the condition becomes true.

intermediate

Give an example of a simple custom expected condition function in Selenium Python.

Example: def element_has_text(locator, text): def _predicate(driver): element = driver.find_element(*locator) return element.text == text return _predicate

What does a custom expected condition in Selenium Python typically return when the condition is met?

A False

B A truthy value or the element

C An exception

D None

When the condition is met, the custom expected condition returns a truthy value, often the element found, so WebDriverWait knows to stop waiting.

Which method must a class implement to be used as a custom expected condition in Selenium Python?

A find_element

B __init__

C wait

D __call__

The __call__ method allows the class instance to be called like a function, which WebDriverWait uses to check the condition.

Why might you write a custom expected condition instead of using built-in ones?

A To handle unique waiting scenarios not covered by built-in conditions

B Because built-in conditions are deprecated

C To avoid using WebDriverWait

D To speed up test execution

Custom expected conditions let you wait for specific, complex conditions unique to your application.

What should a custom expected condition return if the condition is not yet met?

A An exception

B True

C False or None

D The driver object

Returning False or None tells WebDriverWait to keep waiting until the timeout or the condition becomes true.

Which Selenium class is commonly used with custom expected conditions to wait for conditions?

A WebDriverWait

B ActionChains

C Select

D ChromeOptions

WebDriverWait repeatedly calls the expected condition until it returns a truthy value or times out.

Explain how to create and use a custom expected condition in Selenium Python.

Think about how Selenium waits for elements or states.

Describe why custom expected conditions improve test reliability.

Consider real-life waiting situations that built-in waits can't handle.