selenium meetup sf talk march 2014 selenium at scale

Selenium atSalesforce Scale

David LouvtonLead Engineer

dlouvton@salesforce.com

Sagar WanaseljaLead Engineer

Corporate Pres – PowerPoint Template – 4x3 FY14.pptx

• About Salesforce engineering• Operating a selenium farm• Selenium design patterns• Overcoming test failures• Q&A

Agenda

Salesforce Scale

• 3:2 ratio for developers : quality engineers• everyone is a software engineer; role varies• selenium committers on staff (Jim Evans, Luke Inman)

• Data centers with thousands of VMs for automation• multimillion dollar investment• using vmware (VShere), OpenStack and EC2

• 500 commits per day• ~120 software engineering teams

Why Salesforce loves WebDriver

WebDriver is the only test framework in our current arsenal that truly mimics an end-user’s experience• We don’t mock anything• We test against a live app• We suffer the pain of latency• We test end to end on almost every action

WebDriver tests can catch things other levels of tests can’t• Multi-platform consistency• DOM consistency• Rendering issues• Catching inconsistency between

app layers

UI Testing Portfolio

• 50,000 unique Selenium tests• 7,500 unique WebDriver tests

• full “browser compatibility”: IE6-IE11, Firefox, Chrome, Safari• some can run in headless browser like Phantom JS

• 2,000 javascript unit tests• no DOM required• 10ms average execution time

1,000,000 browser tests per day

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The Selenium Infrastructure● Automatically creating, assigning, closing and reopening

bug reports for test failures and flapping tests .

● Test jobs must meet failure thresholds (99%+). Code lines are locked for teams under thresholds

● Support for all combinations of OS & Browser using portable VM Templates, creating deterministic and identical test environments

Issues of scale

• Assigning test failures to the responsible engineer• Non deterministic tests (flappers) and re-runs• Selenium jar upgrades are challenging• Browser upgrades are challenging

• IT and automation ops provide different versions• Large suites: adjust run frequency, deprecate old tests

Salesforce UI Testing Pattern

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Proper Page Objects Encapsulate Selenium

• Make an API of your page for your test• No imports for “openqa” or “selenium.org” in your test• All references to driver & selenium in the page object• Fail fast - call the page object factory in test setup• No assertions in page objects (or any test utility)• Share page objects across engineering teams

• developer complete UI should have a page object• if you can’t make one it’s not a testable page• dependency challenges at scale

Challenges for Mobile Platforms

• Adapting page objects to platform specific UI elements• Screen sizes and adaptive layouts

• “stage left” - switching into contained apps• lightweight page objects = widgets

• Avoid browser or platform specific code in actual tests• establish context elsewhere in utils or page objects

• Automated tests in emulators (99%+)• manual tests on devices before release• exception: testing video

Sagar WanaseljaLead Engineer

swanaselja@salesforce.com

Problematic WebDriver Test

Better WebDriver Test

PageObject WebDriver Test

Diagnosing Test Failures

• Screenshot and HTML capture at failure point• AssertionError or RuntimeException

• Differences between localhost and automation VM• Optimistic timing assumptions

• javascript, rendering, server response, etc.• Defensive “negative” testing• Getting to 100% tests passing

Pro Tips

• Version tests and app code (and configuration) together• Use the Page Object model• Use the API to set up the test, not the UI• Anticipate Selenium and Browser releases• Allocate capacity to browsers most used by customers

• log the user agent on every page view

More Pro Tips

• Avoid using xpath selectors• Complex DOM makes xpath evaluation much slower• Some xpaths are not properly evaluated in WebDriver

• When working with popups make sure you return focus to the main window

• For static/simple HTML pages consider the HtmlUnitDriver

Mature Quality Strategies

• Selenium for dynamic security vulnerability analysis• Pixel perfect image diffs• Accessibility testing (tab completion)• Testing javascript with unit tests

• Selenium is for testing browser compatibility and DOM