What design patterns do you usually apply in your work?

In QA Automation work, I often use the following design patterns:

• Page Object — for structuring tests and separating UI interaction logic from the tests themselves. This improves readability and maintainability.
• Singleton — for creating a single instance of the browser driver or other resources to avoid unnecessary initializations.
• Factory — for creating test data objects or test scenarios with different parameters.
• Decorator — for extending the functionality of tests or steps without changing the original code.

For example, the Page Object pattern allows describing a page as a class with methods for interaction:

class LoginPage:
    def __init__(self, driver):
        self.driver = driver

    def enter_username(self, username):
        self.driver.find_element_by_id('username').send_keys(username)

    def enter_password(self, password):
        self.driver.find_element_by_id('password').send_keys(password)

    def submit(self):
        self.driver.find_element_by_id('submit').click()

This simplifies writing and maintaining tests.