Error guessing test for login form

Preconditions (1)

Step 1: Enter an invalid email format 'user@@example.com' in the email field

Step 2: Enter a valid password 'Password123!' in the password field

Step 3: Click the Login button

Step 4: Verify that an error message 'Invalid email format' is displayed

Step 5: Enter a valid email 'user@example.com' in the email field

Step 6: Leave the password field empty

Step 7: Click the Login button

Step 8: Verify that an error message 'Password cannot be empty' is displayed

Step 9: Enter a valid email 'user@example.com' in the email field

Step 10: Enter a password with less than 6 characters '123' in the password field

Step 11: Click the Login button

Step 12: Verify that an error message 'Password too short' is displayed

✅ Expected Result: The application shows appropriate error messages for each invalid input scenario.

Automation Requirements - Selenium with Python

Assertions Needed:

Verify error message text matches expected for invalid email

Verify error message text matches expected for empty password

Verify error message text matches expected for short password

Best Practices:

Use explicit waits to wait for error messages to appear

Use descriptive locators like By.ID or By.CSS_SELECTOR

Use Page Object Model to separate page actions and test logic

Avoid hardcoded sleeps

Use clear assertion messages

Automated Solution

Testing Fundamentals

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
import unittest

class LoginPage:
    def __init__(self, driver):
        self.driver = driver
        self.email_input = (By.ID, 'email')
        self.password_input = (By.ID, 'password')
        self.login_button = (By.ID, 'login-btn')
        self.error_message = (By.ID, 'error-msg')

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

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

    def click_login(self):
        self.driver.find_element(*self.login_button).click()

    def get_error_message(self):
        wait = WebDriverWait(self.driver, 10)
        error_element = wait.until(EC.visibility_of_element_located(self.error_message))
        return error_element.text

class TestLoginErrorGuessing(unittest.TestCase):
    def setUp(self):
        self.driver = webdriver.Chrome()
        self.driver.get('https://example.com/login')
        self.login_page = LoginPage(self.driver)

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

    def test_invalid_email_format(self):
        self.login_page.enter_email('user@@example.com')
        self.login_page.enter_password('Password123!')
        self.login_page.click_login()
        error = self.login_page.get_error_message()
        self.assertEqual(error, 'Invalid email format', 'Error message for invalid email is incorrect')

    def test_empty_password(self):
        self.login_page.enter_email('user@example.com')
        self.login_page.enter_password('')
        self.login_page.click_login()
        error = self.login_page.get_error_message()
        self.assertEqual(error, 'Password cannot be empty', 'Error message for empty password is incorrect')

    def test_short_password(self):
        self.login_page.enter_email('user@example.com')
        self.login_page.enter_password('123')
        self.login_page.click_login()
        error = self.login_page.get_error_message()
        self.assertEqual(error, 'Password too short', 'Error message for short password is incorrect')

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

This test script uses Selenium WebDriver with Python's unittest framework.

The LoginPage class follows the Page Object Model. It stores locators and methods to interact with the login page elements. This keeps the test code clean and easy to maintain.

Each test method performs one error guessing scenario by entering invalid inputs and clicking the login button.

Explicit waits are used to wait for the error message to appear before reading its text. This avoids flaky tests.

Assertions check that the error messages shown match the expected text for each invalid input.

The setup and teardown methods open and close the browser for each test, ensuring a fresh start.

This approach follows best practices like using descriptive locators, explicit waits, and clear assertion messages.

Common Mistakes - 4 Pitfalls

Using time.sleep() instead of explicit waits

Using brittle XPath locators that break easily

Not clearing input fields before typing

Combining multiple test scenarios in one test method

Bonus Challenge

Now add data-driven testing with 3 different invalid input sets for email and password

Show Hint