Data providers pattern in Selenium Python - Test Execution Trace

Test Overview

This test uses the data providers pattern to run the same login test with multiple username and password pairs. It verifies that the login succeeds for each set of credentials.

Test Code - unittest

Selenium Python

import unittest
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 LoginTest(unittest.TestCase):
    @classmethod
    def setUpClass(cls):
        cls.driver = webdriver.Chrome()
        cls.driver.implicitly_wait(5)

    @classmethod
    def tearDownClass(cls):
        cls.driver.quit()

    def login_test(self, username, password):
        driver = self.driver
        driver.get('https://example.com/login')
        username_field = driver.find_element(By.ID, 'username')
        password_field = driver.find_element(By.ID, 'password')
        login_button = driver.find_element(By.ID, 'login-btn')

        username_field.clear()
        username_field.send_keys(username)
        password_field.clear()
        password_field.send_keys(password)
        login_button.click()

        WebDriverWait(driver, 10).until(
            EC.presence_of_element_located((By.ID, 'welcome-msg'))
        )
        welcome_text = driver.find_element(By.ID, 'welcome-msg').text
        self.assertIn('Welcome', welcome_text)

    def test_login_with_multiple_users(self):
        test_data = [
            ('user1', 'pass1'),
            ('user2', 'pass2'),
            ('user3', 'pass3')
        ]
        for username, password in test_data:
            with self.subTest(username=username):
                self.login_test(username, password)

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

Execution Trace - 8 Steps

Step	Action	System State	Assertion	Result
1	Test starts and Chrome browser opens	Browser window is open	—	PASS
2	Navigate to login page for user1	Login page loaded with username and password fields	—	PASS
3	Find username, password fields and login button	Elements located by IDs: username, password, login-btn	—	PASS
4	Enter username 'user1' and password 'pass1', then click login	Login form submitted	—	PASS
5	Wait until element with ID 'welcome-msg' is present	Welcome message element appears	Check that welcome message text contains 'Welcome'	PASS
6	Repeat steps 2-5 for user2 with password 'pass2'	Login page loaded and login successful for user2	Welcome message contains 'Welcome'	PASS
7	Repeat steps 2-5 for user3 with password 'pass3'	Login page loaded and login successful for user3	Welcome message contains 'Welcome'	PASS
8	Test ends and browser closes	Browser window closed	—	PASS

Failure Scenario

Failing Condition: If the welcome message element does not appear after login or text does not contain 'Welcome'

Execution Trace Quiz - 3 Questions

What does the test verify after clicking the login button?

A That the welcome message with 'Welcome' text appears

B That the login button is disabled

C That the username field is cleared

D That the password field shows the password

Key Result

Using data providers pattern with subTest allows running the same test logic for multiple data sets cleanly and reports each case separately.

Practice

1. What is the main purpose of using the data providers pattern in Selenium Python tests?

easy

A. To generate test reports in different formats

B. To speed up the browser loading time

C. To create new test cases automatically

D. To run the same test multiple times with different input data

Solution

1. Step 1: Understand the data providers pattern

   The data providers pattern allows running one test repeatedly with different sets of data.

2. Step 2: Identify the main benefit

   This helps find more bugs by testing various inputs without writing separate tests.

3. Final Answer:

   To run the same test multiple times with different input data -> Option D

4. Quick Check:

   Data providers = run test many times with different data [OK]

Hint: Remember: data providers = repeat test with new data [OK]

Common Mistakes:

• Thinking data providers speed up browser loading
• Confusing data providers with automatic test creation
• Believing data providers generate reports

2. Which of the following is the correct syntax to use a data provider in pytest for Selenium Python?

easy

A. @pytest.mark.parametrize('input', ['data1', 'data2'])

B. @pytest.run_with_data(['data1', 'data2'])

C. @pytest.test_data(['data1', 'data2'])

D. @pytest.data_provider(['data1', 'data2'])

Solution

1. Step 1: Recall pytest data provider syntax

   Pytest uses @pytest.mark.parametrize to supply multiple data sets to a test function.

2. Step 2: Match the correct syntax

   @pytest.mark.parametrize('input', ['data1', 'data2']) correctly shows @pytest.mark.parametrize('input', ['data1', 'data2']).

3. Final Answer:

   @pytest.mark.parametrize('input', ['data1', 'data2']) -> Option A

4. Quick Check:

   Pytest data provider = @pytest.mark.parametrize [OK]

Hint: Look for @pytest.mark.parametrize for data providers [OK]

Common Mistakes:

• Using non-existent decorators like @pytest.data_provider
• Confusing parametrize with test_data or run_with_data
• Missing quotes around parameter names

3. What will be the output of the following pytest test using data providers?

import pytest

@pytest.mark.parametrize('num', [1, 2, 3])
def test_is_positive(num):
    assert num > 0

medium

A. All tests pass

B. All tests fail

C. Only the test with num=1 passes

D. Syntax error occurs

Solution

1. Step 1: Analyze the test logic

   The test asserts that the input number is greater than zero.

2. Step 2: Check each data value

   Values 1, 2, and 3 are all greater than zero, so all assertions pass.

3. Final Answer:

   All tests pass -> Option A

4. Quick Check:

   All nums > 0, so tests pass [OK]

Hint: Check if all inputs satisfy the assertion [OK]

Common Mistakes:

• Assuming some inputs fail without checking values
• Thinking syntax error due to parametrize
• Ignoring that all numbers are positive

4. Identify the error in this pytest data provider usage:

@pytest.mark.parametrize('input', [1, 2, 3])
def test_example():
    assert input > 0

medium

A. Wrong decorator name

B. Missing parameter in test function definition

C. List of inputs should be strings

D. Assertion syntax is incorrect

Solution

1. Step 1: Check test function parameters

   The test function must accept the parameter named in parametrize, here 'input'.

2. Step 2: Identify missing parameter

   The function test_example() has no parameters, so 'input' is undefined inside it.

3. Final Answer:

   Missing parameter in test function definition -> Option B

4. Quick Check:

   Parametrize param must match function argument [OK]

Hint: Function must accept all parametrize arguments [OK]

Common Mistakes:

• Forgetting to add parameter to test function
• Using wrong decorator name
• Thinking input list must be strings
• Misreading assertion syntax

5. You want to test a login form with multiple username and password pairs using data providers in pytest. Which approach correctly handles multiple parameters?

hard

A. @pytest.mark.parametrize('username', ['user1', 'user2'])
@pytest.mark.parametrize('password', ['pass1', 'pass2'])
def test_login(username, password):
assert username and password

B. @pytest.mark.parametrize('username_password', [('user1', 'pass1'), ('user2', 'pass2')])
def test_login(username_password):
assert username_password[0] and username_password[1]

C. @pytest.mark.parametrize(('username', 'password'), [('user1', 'pass1'), ('user2', 'pass2')])
def test_login(username, password):
assert username and password

D. @pytest.mark.parametrize('username', ['user1', 'user2'], 'password', ['pass1', 'pass2'])
def test_login(username, password):
assert username and password

Solution

1. Step 1: Understand multiple parameter usage in parametrize

   To pass multiple parameters together, use a tuple of parameter names and a list of tuples with values.

2. Step 2: Identify correct syntax

   @pytest.mark.parametrize(('username', 'password'), [('user1', 'pass1'), ('user2', 'pass2')]) def test_login(username, password): assert username and password uses @pytest.mark.parametrize(('username', 'password'), [('user1', 'pass1'), ('user2', 'pass2')]), which is correct.

3. Final Answer:

   Use tuple of parameter names and list of tuples for values -> Option C

4. Quick Check:

   Multiple params = tuple names + list of tuples [OK]

Hint: Use tuple of names and list of tuples for multiple params [OK]

Common Mistakes:

• Stacking multiple parametrize decorators incorrectly
• Passing multiple parameters in one string without tuple
• Wrong syntax with multiple lists in one decorator