Test functions and classes in Selenium Python - Build an Automation Script

Verify login functionality using test functions and classes

Preconditions (2)

Step 1: Open the login page URL

Step 2: Enter 'testuser' in the username input field with id 'username'

Step 3: Enter 'Test@1234' in the password input field with id 'password'

Step 4: Click the login button with id 'loginBtn'

Step 5: Wait for the page to load and verify the URL is 'https://example.com/dashboard'

Step 6: Verify that the element with id 'welcomeMessage' contains text 'Welcome, testuser!'

✅ Expected Result: User is successfully logged in and redirected to the dashboard page with a welcome message displayed

Automation Requirements - pytest with selenium

Assertions Needed:

Assert current URL is 'https://example.com/dashboard'

Assert welcome message text is 'Welcome, testuser!'

Best Practices:

Use pytest test functions and classes to organize tests

Use Selenium explicit waits to wait for elements

Use Page Object Model to separate page interactions

Use setup and teardown methods for browser management

Automated Solution

Selenium Python

import pytest
from selenium import webdriver
from selenium.webdriver.common.by import By
from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.support import expected_conditions as EC

class LoginPage:
    def __init__(self, driver):
        self.driver = driver
        self.username_input = (By.ID, 'username')
        self.password_input = (By.ID, 'password')
        self.login_button = (By.ID, 'loginBtn')

    def load(self):
        self.driver.get('https://example.com/login')

    def login(self, username, password):
        WebDriverWait(self.driver, 10).until(
            EC.visibility_of_element_located(self.username_input)
        ).send_keys(username)
        self.driver.find_element(*self.password_input).send_keys(password)
        self.driver.find_element(*self.login_button).click()

class DashboardPage:
    def __init__(self, driver):
        self.driver = driver
        self.welcome_message = (By.ID, 'welcomeMessage')

    def wait_for_dashboard(self):
        WebDriverWait(self.driver, 10).until(
            EC.url_to_be('https://example.com/dashboard')
        )

    def get_welcome_text(self):
        return WebDriverWait(self.driver, 10).until(
            EC.visibility_of_element_located(self.welcome_message)
        ).text

class TestLogin:
    def setup_method(self):
        self.driver = webdriver.Chrome()
        self.driver.maximize_window()

    def teardown_method(self):
        self.driver.quit()

    def test_valid_login(self):
        login_page = LoginPage(self.driver)
        dashboard_page = DashboardPage(self.driver)

        login_page.load()
        login_page.login('testuser', 'Test@1234')

        dashboard_page.wait_for_dashboard()

        assert self.driver.current_url == 'https://example.com/dashboard'
        assert dashboard_page.get_welcome_text() == 'Welcome, testuser!'

This test script uses pytest and selenium to automate the login test case.

We define two page classes: LoginPage and DashboardPage to separate page actions and locators, following the Page Object Model.

The TestLogin class contains setup and teardown methods to open and close the browser for each test method.

The test method test_valid_login performs the login steps, waits for the dashboard page to load, and asserts the URL and welcome message text.

Explicit waits ensure elements are ready before interacting, improving test reliability.

Common Mistakes - 4 Pitfalls

Using time.sleep() instead of explicit waits

Not closing the browser after tests

Mixing locators directly in test methods

Hardcoding URLs and credentials inside test methods

Bonus Challenge

Now add data-driven testing with 3 different username and password combinations

Show Hint

Practice

1. What is the main purpose of using test functions and classes in Selenium Python testing?

easy

A. To organize tests clearly and run them easily

B. To make the code run faster

C. To avoid writing any assertions

D. To skip browser setup

Solution

1. Step 1: Understand test organization

   Test functions and classes help group related tests logically.

2. Step 2: Recognize ease of running tests

   Using classes and functions allows running tests easily with frameworks like unittest.

3. Final Answer:

   To organize tests clearly and run them easily -> Option A

4. Quick Check:

   Test organization = To organize tests clearly and run them easily [OK]

Hint: Tests group checks for clarity and easy running [OK]

Common Mistakes:

• Thinking tests speed up code execution
• Believing assertions are optional
• Ignoring setup and teardown roles

2. Which of the following is the correct way to define a test method inside a unittest.TestCase class in Selenium Python?

easy

A. def test_example(self):

B. def example_test():

C. def TestExample(self):

D. def _test_example(self):

Solution

1. Step 1: Recall unittest naming conventions

   Test methods must start with 'test' and accept 'self' as first parameter.

2. Step 2: Check method definitions

   Only 'def test_example(self):' follows correct naming and signature.

3. Final Answer:

   def test_example(self): -> Option A

4. Quick Check:

   Method name starts with 'test' and has 'self' [OK]

Hint: Test methods start with 'test' and include self [OK]

Common Mistakes:

• Omitting 'self' parameter
• Not starting method name with 'test'
• Using uppercase 'Test' prefix

3. What will be the output when running this test code snippet?

import unittest

class MyTest(unittest.TestCase):
    def test_pass(self):
        self.assertEqual(2 + 2, 4)

    def test_fail(self):
        self.assertTrue(False)

if __name__ == '__main__':
    unittest.main(exit=False)

medium

A. Both tests pass

B. One test passes, one test fails

C. Both tests fail

D. Syntax error occurs

Solution

1. Step 1: Analyze test_pass method

   assertEqual(2 + 2, 4) is True, so test_pass passes.

2. Step 2: Analyze test_fail method

   assertTrue(False) fails, so test_fail fails.

3. Final Answer:

   One test passes, one test fails -> Option B

4. Quick Check:

   One True, one False assertion = One test passes, one test fails [OK]

Hint: Check each assertion's truth to predict pass/fail [OK]

Common Mistakes:

• Assuming all tests pass
• Ignoring assertTrue(False) fails
• Expecting syntax errors

4. Identify the error in this Selenium Python unittest code:

import unittest
from selenium import webdriver

class TestLogin(unittest.TestCase):
    def setUp(self):
        self.driver = webdriver.Chrome()

    def test_login(self):
        self.driver.get('http://example.com')
        self.assertIn('Example', self.driver.title)

    def tearDown(self):
        self.driver.quit()

if __name__ == '__main__':
    unittest.main()

medium

A. webdriver.Chrome() requires path argument

B. Missing call to super() in setUp and tearDown

C. No error; code is correct

D. assertIn should be assertEquals

Solution

1. Step 1: Review setup and teardown methods

   setUp creates driver; tearDown quits it properly.

2. Step 2: Check assertion and webdriver usage

   assertIn checks substring in title correctly; webdriver.Chrome() works if driver is in PATH.

3. Final Answer:

   No error; code is correct -> Option C

4. Quick Check:

   Standard unittest setup and teardown used [OK]

Hint: Check if setup/teardown and assertions follow unittest rules [OK]

Common Mistakes:

• Assuming webdriver.Chrome() always needs path
• Confusing assertIn with assertEquals
• Forgetting to quit driver in tearDown

5. You want to run multiple Selenium tests that share the same browser setup and cleanup. Which unittest structure best achieves this?

hard

A. Call unittest.main() inside each test method

B. Write separate test functions without any setup or teardown

C. Create a new webdriver instance inside each test method

D. Use a TestCase class with setUpClass and tearDownClass class methods

Solution

1. Step 1: Understand shared setup/cleanup needs

   setUpClass and tearDownClass run once for all tests in a class, ideal for shared browser setup.

2. Step 2: Evaluate other options

   Separate functions lack shared setup; new webdriver per test is inefficient; unittest.main() runs all tests, not per method.

3. Final Answer:

   Use a TestCase class with setUpClass and tearDownClass class methods -> Option D

4. Quick Check:

   Shared setup/cleanup = setUpClass/tearDownClass [OK]

Hint: Use setUpClass/tearDownClass for shared browser setup [OK]

Common Mistakes:

• Creating driver in each test wastes resources
• Calling unittest.main() multiple times causes errors
• Skipping setup causes flaky tests