Sahi is a web automation tool that uses JavaScript and proxy injection to simplify browser automation and testing. It provides normalized APIs to access elements on the page and simulate user events across different browsers. Sahi scripts are executed by injecting JavaScript code into the browser via a proxy. This allows Sahi to work across domains and handle issues like page refreshes. The APIs and architecture aim to make Sahi easy for testers to use while still being powerful enough for developers.

1. Principles and Architecture of Sahi
- Web Automation Simplified
Narayan Raman

2. Primary Problem
Verify web application functionality
NOT
Build a browser automation tool or library

3. Browser or No Browser?
• At the protocol level – Parse extract and verify
– Problem: No Javascript, no AJAX
• At the browser
– Advantage:
• Closer to the real world
• Handles Javascript/AJAX etc.
BROWSER WINS

4. Browsers
• IE, Firefox, Chrome, Safari, Opera
• Multitude of Versions, often releasing rapidly
• No standards around browser automation
APIs
– No financial motivation for browser vendors to
add these APIs and maintain them, especially on
older versions

5. What the Tool needs to do
• Access elements on the browser using some
API
• Simulate events such that they match the real
user

6. Possibilities?
• Write wrappers around every browser, past
and present
• Use something else

7. Constraints
• Developer time and expertise
– Knowledge required of various browsers and their
architectures
– Need too many experts on too many languages
– Need to be able to support and reproduce issues
across multiple browser/OS combinations
• Lack of standards around browser automation
APIs

8. Something Else? Javascript
• Running Javascript is one of the core features
of every browser.
• Javascript can both identify elements (via the
DOM) and simulate events.
• Small impediments:
– Events generated on different browsers are
different
– The DOM may be different across browsers

9. Using Javascript
• Normalized/Simplified APIs to access DOM
• Normalized APIs for event simulation which
are tailored for different browsers
Let us call it Sahi APIs
• Is that it?

10. Execution?
• How does the web page have access to these
APIs?
– Script src tag may be?
<script src=“sahiapis.js”></script>
Let us assume that

11. Execution? Contd.
• Where is the script?
– Add a js function to read a file (via an
intermediate server) and execute it on the page
• Consider a 3 line script
1 _setValue(_textbox(“login”), “user me”);
2 _click(_submit(“Login”));
// page refreshes
3 _click(_button(“Compose”));

12. Execution? Contd.
• Page refresh flushes js memory/state
• Who remembers that the script is on line 3?
– Need a memory space which does not change
with each page load
– May be in an Iframe or new window?

13. Problems
• Frame busting code
• Javascript Security:
– Loosely put, page from one domain cannot talk to
another

14. Solution
• Proxy injection
– All browsers understand proxies and will continue
to do so
– Proxies let you inject code into web pages which
the browser thinks is from the same domain
– Can even work across domains, using the same
techniques that are used for valid cross domain
communication

15. Design Considerations
• Aimed at Developers or Testers?
– Testers
• Should be simple to learn and use
• Should resort to as little code as possible
• Helpers like recorders, object spy etc. are necessary
• Should the Sahi language be scriptable?
– Sahi should read easily like DSL
– But also be scriptable for added power

16. Language choice for Sahi
• Javascript is the language of the Web
• Users anyway need to know Javascript for success
with web projects.
• The backend of web apps may vary from J2EE to
RoR to PHP, but the front end is always HTML and
JS. JS is the ideal choice.
• Sahi Script seamlessly interacts with browser
javascript and also follows the Javascript syntax

17. Advantage of Javascript Events
• Does not need browser window to be in focus
• Can play back multiple browser tests
simultaneously on browsers which allow
cookie seclusion (Eg. Firefox/chrome profiles)

18. Sahi Script – Why not pure JS?
• Needs of a Web Testing DSL
– Should wait for readiness of web page state
– Should recover from errors automatically
– For simplicity, this waiting and recovery should be
internally handled by the DSL rather than by the
user
– More code = more maintenance

19. DEMO

20. Sahi APIs and Parsing
• Parsing done to:
– Keep js code namespaces separate
Eg. _sahi._click – All APIs belong to _sahi object.
• Allows for automatic logging, wait handling
and error recovery

21. Simple Architecture
Sahi
Proxying + js code
injection Web App
Browser
Local Processor
/_s_/ Recorder + Player
Rhino Engine

22. The APIs
• _textbox(“username”)
– “username” may be the name, id, className etc.
Intelligent defaults used. Can be configured.
• APIs automatically recurse across frames and
iframes.

23. Duplicates and Dynamic ids
• Duplicates are indexed
– BUT, indexes may lead to brittle tests.
• Dynamic id patterns – Sahi knows common
patterns to ignore. Can be configured.
– Sahi will use properties other than id for these.

24. Contexts and UI Relations
• Remove index by passing contexts.
– _link(“Edit”, _near(_cell(“Customer 1”)))
• All Sahi APIs can take contexts.
– We call these UI Relations
• Relate dynamic elements with business
concepts which are more concrete.

25. UI Relation APIs
• _near/_in
– DOM based relations
• _under
– Positional relation
Eg. _link(“Edit”, _near(_cell(“Customer 1”)))
Or
_image(0, _near(_cell(“Customer 1”)), _under(_cell(“Delete”)))

26. frames/iframes across domains
• Sahi can handle pages which load multiple
domains inside iframes.
– Eg. Facebook login inside your web app.
• Javascript alone cannot go across
frames/iframes
• But JS + Proxy combination removes the need
for it

27. File Uploads
• Bypass the browser
• Append file content to request from inside the
proxy
• Needs some small documented hack to
handle browser validation of file fields.

28. More Goodness
• Works on any browser which supports a proxy
and javascript.
– Android, iOS browsers too
• Can modify http headers to simulate other
mobile browsers
• Can force IE9 to work as IE7 or IE8 by adding
relevant meta tags

29. Sahi
• Sahi
– Open Source
• Sahi Pro
– Commercial product
Details: http://sahi.co.in/

30. Thank You
V Narayan Raman
http://sahi.co.in
Twitter: @narayanraman
@_sahi
Tyto Software Pvt. Ltd.