Why synchronization prevents flaky tests in Selenium Python - Test Execution Impact

Test Overview

This test checks that synchronization using explicit waits prevents flaky failures by waiting for a button to be clickable before clicking it. It verifies the button click leads to the expected page change.

Test Code - Selenium

Selenium Python

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 TestSynchronization(unittest.TestCase):
    def setUp(self):
        self.driver = webdriver.Chrome()
        self.driver.get('https://example.com/delayed_button')

    def test_click_button_with_wait(self):
        driver = self.driver
        wait = WebDriverWait(driver, 10)
        # Wait until the button is clickable
        button = wait.until(EC.element_to_be_clickable((By.ID, 'delayed-btn')))
        button.click()
        # Verify the page shows success message
        success_msg = wait.until(EC.visibility_of_element_located((By.ID, 'success-msg')))
        self.assertEqual(success_msg.text, 'Button clicked successfully!')

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

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

Execution Trace - 5 Steps

Step	Action	System State	Assertion	Result
1	Test starts and Chrome browser opens	Browser window opened at URL https://example.com/delayed_button	-	PASS
2	WebDriverWait waits up to 10 seconds for button with ID 'delayed-btn' to be clickable	Page is loading, button appears after delay	Button is clickable	PASS
3	Clicks the button with ID 'delayed-btn'	Button clicked, page triggers success message display	-	PASS
4	WebDriverWait waits up to 10 seconds for element with ID 'success-msg' to be visible	Success message appears on page	Success message text equals 'Button clicked successfully!'	PASS
5	Test ends and browser closes	Browser window closed	-	PASS

Failure Scenario

Failing Condition: If synchronization is not used, the test tries to click the button before it is clickable or check the success message before it appears.

Execution Trace Quiz - 3 Questions

What does the explicit wait in this test ensure?

A The test runs without opening a browser

B The button is clickable before clicking it

C The browser opens faster

D The button is hidden before clicking

Key Result

Using explicit waits to synchronize test actions with the web page state prevents flaky tests caused by elements not being ready for interaction.