Network condition testing in Testing Fundamentals - Test Execution Trace

Test Overview

This test checks how a web application behaves when the network is slow or disconnected. It verifies that the app shows a loading message during slow network and an error message when offline.

Test Code - Selenium

Testing Fundamentals

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

    def test_slow_network_loading(self):
        # Simulate slow network using Chrome DevTools Protocol
        self.driver.execute_cdp_cmd('Network.enable', {})
        self.driver.execute_cdp_cmd('Network.emulateNetworkConditions', {
            'offline': False,
            'latency': 2000,  # 2 seconds delay
            'downloadThroughput': 500 * 1024 / 8,  # 500 kbps
            'uploadThroughput': 500 * 1024 / 8
        })

        self.driver.refresh()

        # Wait for loading message
        loading = WebDriverWait(self.driver, 10).until(
            EC.visibility_of_element_located((By.ID, 'loading-message'))
        )
        self.assertEqual(loading.text, 'Loading...')

    def test_offline_error_message(self):
        # Simulate offline mode
        self.driver.execute_cdp_cmd('Network.enable', {})
        self.driver.execute_cdp_cmd('Network.emulateNetworkConditions', {
            'offline': True,
            'latency': 0,
            'downloadThroughput': 0,
            'uploadThroughput': 0
        })

        self.driver.refresh()

        # Wait for error message
        error = WebDriverWait(self.driver, 10).until(
            EC.visibility_of_element_located((By.ID, 'error-message'))
        )
        self.assertEqual(error.text, 'No internet connection')

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

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

Execution Trace - 8 Steps

Step	Action	System State	Assertion	Result
1	Test starts and Chrome browser opens	Browser opened at https://example.com	-	PASS
2	Enable network emulation and set slow network conditions	Network throttling set: 2s latency, 500 kbps throughput	-	PASS
3	Refresh the page to apply network conditions	Page reloads with slow network	-	PASS
4	Wait for loading message element with ID 'loading-message'	Loading message visible on page	Verify loading message text is 'Loading...'	PASS
5	Enable network emulation and set offline mode	Network set to offline	-	PASS
6	Refresh the page to apply offline condition	Page reloads with no network	-	PASS
7	Wait for error message element with ID 'error-message'	Error message visible on page	Verify error message text is 'No internet connection'	PASS
8	Close browser and end test	Browser closed	-	PASS

Failure Scenario

Failing Condition: The network emulation commands fail or the expected elements do not appear within timeout

Execution Trace Quiz - 3 Questions

What does the test verify when the network is slow?

A The page loads instantly

B The page shows an error message

C The page shows a loading message

D The page redirects to another site

Key Result

Using network emulation in tests helps verify app behavior under real-world slow or offline conditions, improving user experience reliability.