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 C#, Groovy, Java, Perl, PHP, Python, Ruby and Scala.
The tests can then be run against most modern web browsers. Selenium deploys on Windows, Linux, and OS X platforms. It is open-source software, released under the Apache 2.0 license, and can be downloaded and used without charge.Components
Selenium IDE is a complete integrated development environment (IDE) for Selenium tests. It is implemented as a Firefox Add-On, 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. It is little-maintained and is compatible with Selenium RC, which was deprecated.
Scripts may be automatically recorded and edited manually providing auto completion 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 anoption), and for retrieving data from the resulting pages.
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
Selenium Remote Control was a refactoring of Driven Selenium or Selenium B designed by Paul Hammant , credited with Jason as co-creator of Selenium. Theoriginal version directly launched a process for the browser in question, from the test language of Java, .Net, Python or Ruby. The wire protocol (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 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 an Html Unit browser driver, which simulates a browser using HtmlUnit.
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 Domain 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.
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 July 2012, the working draft was released. Selenium-Webdriver (Selenium 2.0) is fully implemented and supported in Python, Ruby, Java, and C#.
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 running tests in parallel on multiple machines, and to manage different browser versions and browser configurations centrally (instead of in each individual test).
The ability to run tests on remote browser instances is useful to spread the load of testing across several machines, and to run tests in browsers running on different platforms or operating systems. The latter is particularly useful in cases where not all browsers to be used for testing can run on the same platform.