Synthetic Testing

Detailed explanation

Synthetic testing, also known as proactive monitoring or active monitoring, is a crucial technique in modern software testing and monitoring strategies. It involves creating and executing simulated user transactions to proactively assess the performance, availability, and functionality of applications and systems. Unlike passive monitoring, which relies on analyzing real user traffic, synthetic testing generates its own traffic, allowing for controlled and repeatable testing scenarios. This proactive approach enables teams to identify and resolve issues before they impact real users, leading to improved user experience and reduced downtime.

Why Use Synthetic Testing?

Several key benefits drive the adoption of synthetic testing:

• Proactive Issue Detection: Synthetic tests run continuously, even when there's no real user activity. This allows you to detect problems early, often before they affect actual users. For example, a synthetic test can alert you to a slow database query during off-peak hours, giving you time to fix it before the morning rush.
• Baseline Performance Monitoring: By running the same synthetic tests repeatedly, you can establish a performance baseline for your application. Deviations from this baseline can indicate performance degradation or other issues.
• Third-Party Service Monitoring: Synthetic testing can be used to monitor the performance and availability of third-party services that your application depends on, such as APIs, CDNs, and payment gateways. This is particularly important for applications that rely heavily on external services.
• Geographic Performance Testing: Synthetic tests can be executed from different geographic locations to assess the application's performance in various regions. This is crucial for applications with a global user base.
• Testing Before Release: Synthetic tests can be incorporated into your CI/CD pipeline to ensure that new releases meet performance and availability requirements before they are deployed to production.
• Simulating User Journeys: Complex user flows, such as placing an order in an e-commerce application, can be simulated to ensure that all steps in the journey are functioning correctly.

Practical Implementation

Implementing synthetic testing involves several steps:

1. Define Test Scenarios: Identify the critical user flows and functionalities that need to be monitored. These scenarios should reflect the most common and important user interactions with the application.
2. Create Test Scripts: Develop scripts that simulate the defined user scenarios. These scripts typically involve sending HTTP requests, interacting with UI elements, and validating responses.
3. Choose a Testing Tool: Select a synthetic testing tool that meets your needs. Several commercial and open-source tools are available, each with its own strengths and weaknesses.
4. Configure Test Execution: Configure the testing tool to execute the scripts at regular intervals from different locations.
5. Analyze Results and Set Alerts: Analyze the test results to identify performance bottlenecks and availability issues. Set up alerts to notify you when tests fail or when performance degrades beyond acceptable thresholds.

Example using Selenium and Python

Here's a simple example of a synthetic test using Selenium and Python to check if a website is accessible:

from selenium import webdriver
from selenium.webdriver.chrome.options import Options
import time
 
def check_website_availability(url):
    chrome_options = Options()
    chrome_options.add_argument("--headless")  # Run Chrome in headless mode
    driver = webdriver.Chrome(options=chrome_options) # Ensure chromedriver is in your PATH
    try:
        driver.get(url)
        print(f"Website {url} is accessible. Title: {driver.title}")
        return True
    except Exception as e:
        print(f"Website {url} is not accessible. Error: {e}")
        return False
    finally:
        driver.quit()
 
if __name__ == "__main__":
    website_url = "https://www.example.com"
    is_available = check_website_availability(website_url)
    if is_available:
        print("Test passed.")
    else:
        print("Test failed.")
    time.sleep(5) #Wait 5 seconds

This script uses Selenium to open a website in a headless Chrome browser and checks if the website loads successfully. The --headless argument ensures that the browser runs in the background without a graphical user interface, making it suitable for automated testing. Error handling is included to catch exceptions that may occur if the website is unavailable. The time.sleep(5) is added to simulate a longer test duration.

Best Practices

• Prioritize Critical Transactions: Focus on testing the most important user flows and functionalities.
• Use Realistic Data: Use realistic data in your test scripts to simulate real user behavior.
• Monitor Third-Party Services: Monitor the performance and availability of all third-party services that your application depends on.
• Test from Multiple Locations: Test your application from different geographic locations to ensure consistent performance for all users.
• Integrate with CI/CD: Integrate synthetic testing into your CI/CD pipeline to ensure that new releases meet performance and availability requirements.
• Regularly Review and Update Tests: Review and update your synthetic tests regularly to reflect changes in your application and user behavior.
• Implement Robust Alerting: Set up alerts to notify you when tests fail or when performance degrades beyond acceptable thresholds. Ensure that alerts are actionable and provide sufficient information to diagnose the problem.
• Avoid Overly Complex Scripts: Keep your test scripts as simple and focused as possible. Complex scripts can be difficult to maintain and debug.
• Use Parameterization: Use parameterization to make your test scripts more flexible and reusable. For example, you can parameterize the URLs, usernames, and passwords used in your tests.

Common Tools

• Selenium: A popular open-source framework for automating web browsers.
• Puppeteer: A Node.js library for controlling headless Chrome or Chromium.
• Playwright: A Node.js library to automate Chromium, Firefox and WebKit with a single API.
• New Relic Synthetics: A commercial synthetic monitoring tool that provides a wide range of features, including browser monitoring, API monitoring, and transaction monitoring.
• Datadog Synthetic Monitoring: A commercial synthetic monitoring tool that integrates with Datadog's other monitoring and analytics products.
• Uptrends: A commercial website monitoring tool that offers synthetic testing capabilities.
• Checkly: A commercial API and E2E monitoring platform.

Synthetic testing is an invaluable tool for ensuring the reliability and performance of modern software applications. By proactively simulating user behavior, teams can identify and resolve issues before they impact real users, leading to improved user experience and reduced downtime.

Further reading

• Selenium Documentation
• Puppeteer Documentation
• Playwright Documentation
• New Relic Synthetics
• Datadog Synthetic Monitoring
• Uptrends Website Monitoring
• Checkly API and E2E Monitoring