1. Web Performance Testing
with WebDriver
Tools, Tips, and Techniques
Michael Klepikov
Make the Web Faster Team, Google
@MTWFG
webpagetest.org

2. Why is it important?
■ +1s load => -7% conversion rate
■ Just better user experience
■ Mobile exacerbates slowness
■ 46% mobile users abandon after 10s

3. Page Load performance
■ WebPageTest.org
■ Waterfall chart
■ Simulated latency
■ Many iterations for statistical validity

4. Interactive scenarios
■ Multi-page
■ Login
■ Ordering sequence
■ AJAX is a better user experience

5. Marry WD + WebPageTest
■ Use functional tests for performance
■ Measure performance while test runs
■ Not quite as trivial as it seems

6. WPT + WD Security
■ Sandboxing Java is hard, JS is easy
■ WebDriverJS FTW
○ NodeJS VM API
■ Submit a WDJS script to WPT

7. Google Instant Search - WDJS
driver = new webdriver.Builder().build();
driver.get('http://www.google.com');
driver.findElement(webdriver.By.name('q'))
.sendKeys('webdriver');
driver.findElement(webdriver.By.name('btnG'))
.click();
driver.wait(function() {
return driver.getTitle();
});

8. Google Instant Search - result

9. Measure around WD calls?
■ Test-WD-browser: HTTP JSON RPC
■ WD has 200ms wait loops
■ Too granular, overhead, variability
■ We want single-ms precision

10. Page self-instrumentation
■ Frameworks exist
○ Boomerang, Episodes, others
■ Page "calls home" with numbers
■ Intercept these while the test runs
○ Parse from URLs in HAR

11. Surrogate instrumentation
■ Post-process a HAR/Timeline
■ Infer action boundaries
■ Future: Resource/User Timings

12. Browser Standards
■ Nav Timings in most major browsers
■ Resource Timings -- not yet
■ User Timings -- not yet
■ Chrome DevTools Timeline
■ Bowsers are moving fast...

13. Do's and Dont's
■ No WD within instrumented intervals
■ Aggregate over multiple iterations!
■ Run frontend in maximum isolation
○ Mock/stub/fake backends
○ Stable, repeatable results