Page Object Model¶

Page Object Model (POM) encapsulates each web page as a class: locators as attributes, actions as methods. Tests interact with page objects, never raw driver calls. One locator change = one class update, not every test. Works with Selenium, Playwright, and mobile (Kaspresso screen objects).

Key Facts¶

Each page/component = one class with locators as class attributes and actions as methods
Assertions belong in tests, NOT in page objects - pages expose data, tests verify
Methods return self or the next page object for chaining
Locators at consistent abstraction level (all "fill field" or all "complete form", not mixed)
Name fields using UI terminology (if form says "Date of Birth", field = date_of_birth)
Component objects (header, nav, footer) extend POM for reusable page sections

Patterns¶

Basic Page Object¶

class LoginPage:
    URL = "/login"
    USERNAME = (By.CSS_SELECTOR, "#username")
    PASSWORD = (By.CSS_SELECTOR, "#password")
    SUBMIT = (By.CSS_SELECTOR, "button[type='submit']")
    ERROR = (By.CSS_SELECTOR, ".error-message")

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

    def open(self, base_url):
        self.driver.get(f"{base_url}{self.URL}")
        return self

    def login(self, username, password):
        self.driver.find_element(*self.USERNAME).clear()
        self.driver.find_element(*self.USERNAME).send_keys(username)
        self.driver.find_element(*self.PASSWORD).clear()
        self.driver.find_element(*self.PASSWORD).send_keys(password)
        self.driver.find_element(*self.SUBMIT).click()
        return MainPage(self.driver)  # returns next page

    def get_error_text(self):
        return self.driver.find_element(*self.ERROR).text

Test Using Page Object¶

def test_login_error(browser, base_url):
    page = LoginPage(browser).open(base_url).login("bad", "creds")
    # Assertion in test, NOT in page object
    assert page.get_error_text() == "Invalid credentials"

Fixture Integration¶

@pytest.fixture
def login_page(browser, base_url):
    return LoginPage(browser).open(base_url)

@pytest.fixture
def authenticated_page(login_page, app_user):
    username, password = app_user
    return login_page.login(username, password)

def test_dashboard(authenticated_page):
    assert authenticated_page.get_title() == "Dashboard"

Kaspresso Screen Objects (Android)¶

object MainScreen : KScreen<MainScreen>() {
    override val layoutId = R.layout.activity_main
    override val viewClass = MainActivity::class.java

    val title = KTextView { withId(R.id.title) }
    val submitButton = KButton { withId(R.id.submit_button) }
}

Gotchas¶

Hiding assertions inside page objects makes failures harder to diagnose
Mixed abstraction levels ("fill name" + "submit entire form" in same class) cause confusion
Deep page hierarchies add complexity - keep it flat unless genuinely needed
Screenshots: capture in fixtures/teardown with unique filenames, not inside page objects