Selenium is a portable software testing framework for web Applications.
Selenium provides a record/playback tool for authoring tests without learning a
test scripting language (Selenium IDE). It
also provides a test domain specific language(Selenese) to write tests in a number of popular
programming languages, including Java,c#,Groovy, Perl,PHP,Python and Ruby. The
tests can then be run against most modern webbrowsers.
Selenium deploys onWindows, Linux, and MAcintosh platforms.
History
Selenium was originally developed by Jason Huggins in 2004, who
was later joined by other programmers and testers at Thoughtworks. It is open
source software, released under the Apache2.0 Licence, and can be
downloaded and used without charge.
The name comes from a joke made by Huggins in an email, mocking a
competitor named Mercury saying that you can cure mercury poisoning by
taking Selenium supplements. The others that received the email took the name
and ran with it.
The latest side project is Selenium Grid, which provides a hub
allowing the running of multiple Selenium tests concurrently on any number of
local or remote systems, thus minimizing test execution time.
Selenium components
Selenium IDE
Selenium IDE is
a complete integrated development environment (IDE) for Selenium tests. It
is implemented as a Firefox Extension, and allows recording, editing, and
debugging tests. It was previously known as Selenium Recorder. Selenium-IDE was
originally created by Shinya Kasatani and donated to the Selenium project in
2006.
Scripts may be automatically recorded and edited manually
providing autocompletion support and the ability to move commands around quickly.
Scripts are recorded in Selenese, a special test
scripting language for Selenium. Selenese provides commands for performing
actions in a browser (click a link, select an option), and for retrieving data
from the resulting pages.
Features:
·
Easy record and playback
·
Intelligent field
selection will use IDs, names, or Xpath as needed
·
Autocomplete for all
common Selenium commands
·
Walkthrough tests
·
Debug and set
breakpoints
·
Save tests as Selenese, Ruby
scripts, or other formats
·
Support for Selenium
user-extensions.js file
·
Option to automatically
assert the title of every page
·
Easy customization
through plugins
Selenium Client API
As an alternative to writing tests in Selenese, tests can also be
written in various programming languages. These tests then communicate with
Selenium by calling methods in the Selenium Client API. Selenium currently
provides client APIs for Java, C#, Ruby and Python.
With Selenium 2, a new Client API was introduced (with WebDriver as
its central component). However, the old API (using class Selenium)
is still supported.
Selenium Remote Control(RC)
Selenium Remote Control (RC) is a server, written in Java. that accepts
commands for the browser via HTTP.RC makes it possible to write automated tests
for a web application in any programming language, which allows for better
integration of Selenium in existing unit test frameworks. To make writing tests
easier, Selenium project currently provides client drivers for PHP,Python ,Ruby,
Java. The Java driver can also be used with JavaScript.A new instance of
selenium RC server is needed to launch html test case - which means that the
port should be different for each parallel run.However for Java/PHP test case
only one Selenium RC instance needs to be running continuously.
Selenium Remote Control was a refactoring of Driven
Selenium or Selenium B designed by Paul Hammant,
credited with Jason as co-creator of Selenium. The original version directly
launched a process for the browser in question, from the test language of Java,
.Net, Python or Ruby. The wire protocol (confusingly called 'Selenese' in its
day) was reimplemented in each language port. After the refactor by Dan
Fabulich, and Nelson Sproul (with help from Pat Lightbody) there was an
intermediate daemon process between the driving test script, and the browser.
The benefits included the ability to drive remote browsers, and the reduced
need to port every line of code to an increasingly growing set of languages. Selenium
Remote Control completely took over from the Driven Selenium code-line
in 2006. The browser pattern for 'Driven'/'B' and 'RC' was response/request,
which subsequently became known as Comet.
With the release of Selenium 2, Selenium RC has been officially
deprecated in favor of Selenium WebDriver.
Selenium WebDriver
Selenium WebDriver is the successor to Selenium RC. Selenium
WebDriver accepts commands (sent in Selenese, or via a Client API) and sends
them to a browser. This is implemented through a browser-specific browser
driver, which sends commands to a browser, and retrieves results. Most
browser drivers actually launch and access a browser application (such as Firefox
or Internet Explorer); there is also a HtmlUnit browser driver, which
simulates a browser using HtmlUnit.
Unlike in Selenium 1, where the Selenium RC server was necessary
to run tests, Selenium WebDriver does not need a special server to execute
tests. Instead, the WebDriver directly starts a browser instance and controls
it. However, Selenium Grid can be used with WebDriver to execute tests on
remote systems (see below).
As of early 2012, Simon Stewart (inventor of WebDriver), who was
then with Google and now with Facebook, and David Burns of Mozilla were
negotiating with the W3C to make WebDriver an internet standard. In early
2013, the working draft was released. As such, Selenium-Webdriver (Selenium
2.0) aims to be the reference implementation of the WebDriver standard in
various programming languages. Currently Selenium-WebDriver is fully
implemented and supported in Python, Ruby, Java, and C#.
In practice, this means that the Selenium 2.0 API has
significantly fewer calls than does the Selenium 1.0 API. Where Selenium 1.0
attempted to provide a rich interface for many different browser operations,
Selenium 2.0 aims to provide a basic set of building blocks from which
developers can create their own Dpmain specific language.
One such DSL already exists: the Watir project in the Ruby language has a
rich history of good design. Watir-webdriver implements the Watir API as a
wrapper for Selenium-Webdriver in Ruby. Watir-webdriver is created entirely
automatically, based on the WebDriver specification and the HTML specification.
Selenium Grid
Selenium Grid is a server that allows tests to use web browser
instances running on remote machines. With Selenium Grid, one server acts as
the hub. Tests contact the hub to obtain access to browser
instances. The hub has a list of servers that provide access to browser
instances (WebDriver nodes), and lets tests use these instances.
Selenium Grid allows to run tests in parallel on multiple machines, and to
manage different browser versions and browser configurations centrally (instead
of in each individual test).
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