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UI Automation

UI automation tests your application through a real browser, like a real user would.

Tool Comparison

Feature Playwright Selenium
Speed Fast Slower
Auto-wait Yes No (manual waits)
Language Python, JS, C#, Java Python, JS, C#, Java, Ruby
Browser support Chromium, Firefox, WebKit Chrome, Firefox, Safari, Edge
Setup Easy Requires driver setup
Recommendation Preferred for new projects Good for legacy projects

Install

uv add playwright
uv run playwright install

Basic Example

from playwright.sync_api import sync_playwright

with sync_playwright() as p:
    browser = p.chromium.launch(headless=True)
    page = browser.new_page()

    page.goto("https://example.com")
    print(page.title())

    browser.close()

Finding Elements (Locators)

page.locator("#username")              # by ID
page.locator(".submit-btn")           # by CSS class
page.locator("[data-testid='login']") # by test ID (recommended)
page.get_by_role("button", name="Submit")  # by role
page.get_by_text("Sign In")                # by text
page.get_by_placeholder("Enter email")     # by placeholder

Use data-testid attributes

Ask developers to add data-testid to elements. These do not change with UI redesigns.

Common Actions

page.fill("#username", "alice")
page.click("#submit")
page.check("#agree-checkbox")
page.select_option("#country", "US")
page.press("#search", "Enter")

text = page.locator(".message").text_content()
is_visible = page.locator(".modal").is_visible()

Wait Strategies

Playwright auto-waits for elements, but you can add explicit waits:

page.wait_for_selector(".result", timeout=5000)
page.locator(".spinner").wait_for(state="hidden")
page.wait_for_url("**/dashboard")

Selenium

Install

uv add selenium

Basic Example

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

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

Finding Elements

from selenium.webdriver.common.by import By

driver.find_element(By.ID, "username")
driver.find_element(By.CSS_SELECTOR, ".submit-btn")
driver.find_element(By.XPATH, "//button[@type='submit']")
driver.find_element(By.NAME, "email")

Explicit Waits

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

wait = WebDriverWait(driver, 10)
element = wait.until(
    EC.presence_of_element_located((By.ID, "result"))
)

Avoid implicit waits

Always use explicit waits. Implicit waits hide timing issues.

pytest + Playwright

Fixture Setup

# tests/conftest.py
import pytest
from playwright.sync_api import Page

@pytest.fixture
def login_page(page: Page) -> Page:
    page.goto("https://staging.example.com/login")
    return page

Test Example

def test_successful_login(login_page: Page):
    login_page.fill("#username", "alice")
    login_page.fill("#password", "secret123")
    login_page.click("#submit")
    assert login_page.url.endswith("/dashboard")

Locator Strategy (Priority)

Priority Locator Type Example
1 (Best) data-testid [data-testid='login-btn']
2 Role + name get_by_role("button", name="Login")
3 Text get_by_text("Submit")
4 CSS selector .login-form .submit
5 (Avoid) XPath //div[@class='form']/button

Best Practices

  • Use Playwright for new projects — it is faster and more stable
  • Use data-testid attributes as primary locators
  • Never use time.sleep() — use proper wait strategies
  • Keep tests independent — each test starts from a clean state
  • Use Page Object Model to organize page interactions
  • Run UI tests in headless mode in CI/CD
  • Test only critical user flows with E2E tests