Selenium

Browser automation framework for web testing.

When to Use

• Cross-browser testing
• Legacy system testing
• Multi-language support
• CI/CD integration

Quick Start

from selenium import webdriver
from selenium.webdriver.common.by import By

driver = webdriver.Chrome()
driver.get("https://example.com")

element = driver.find_element(By.ID, "search")
element.send_keys("test query")
element.submit()

driver.quit()

Core Concepts

Locators

from selenium.webdriver.common.by import By

# Finding elements
driver.find_element(By.ID, "element-id")
driver.find_element(By.NAME, "element-name")
driver.find_element(By.CLASS_NAME, "class-name")
driver.find_element(By.TAG_NAME, "input")
driver.find_element(By.CSS_SELECTOR, ".container > .item")
driver.find_element(By.XPATH, "//div[@class='item']")
driver.find_element(By.LINK_TEXT, "Click here")
driver.find_element(By.PARTIAL_LINK_TEXT, "Click")

# Multiple elements
driver.find_elements(By.CLASS_NAME, "item")

Waits

from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.support import expected_conditions as EC

# Explicit wait
wait = WebDriverWait(driver, 10)
element = wait.until(EC.presence_of_element_located((By.ID, "loaded")))
element = wait.until(EC.element_to_be_clickable((By.ID, "button")))
wait.until(EC.visibility_of_element_located((By.ID, "result")))

# Implicit wait
driver.implicitly_wait(10)

Common Patterns

Page Object Model

class LoginPage:
    def __init__(self, driver):
        self.driver = driver
        self.email_input = (By.ID, "email")
        self.password_input = (By.ID, "password")
        self.submit_button = (By.ID, "submit")

    def enter_email(self, email):
        self.driver.find_element(*self.email_input).send_keys(email)

    def enter_password(self, password):
        self.driver.find_element(*self.password_input).send_keys(password)

    def submit(self):
        self.driver.find_element(*self.submit_button).click()

    def login(self, email, password):
        self.enter_email(email)
        self.enter_password(password)
        self.submit()

Actions

from selenium.webdriver.common.action_chains import ActionChains

actions = ActionChains(driver)

# Mouse actions
actions.move_to_element(element).click().perform()
actions.double_click(element).perform()
actions.context_click(element).perform()  # Right-click
actions.drag_and_drop(source, target).perform()

# Keyboard
actions.send_keys(Keys.ENTER).perform()
actions.key_down(Keys.CONTROL).send_keys('a').key_up(Keys.CONTROL).perform()

Best Practices

Do:

• Use explicit waits
• Implement Page Object Model
• Use headless mode in CI
• Handle stale elements

Don’t:

• Use Thread.sleep
• Chain too many actions
• Skip cleanup
• Ignore exceptions

Troubleshooting

References

• Selenium Documentation
• Selenium Python