Setup Selenium Grid for .NET
I need to run my browser automation tests in parallel as they are painfully slow and I need to be able to provide developers with fast feedback on the state of there changes. Really, what is the point of spending time and effort on creating tests that no one wants to run because they take hours to run. In my opinion it was vital to get this going in order to get a return on the time and effort invested in our browser based test development.
We are a .Net shop and for our situation the best option for parallel browser testing is Selenium Grid, a Java platform. Quick overview, Selenium Grid uses a Hub to distribute tests to Nodes that actually run the test in the selected browser. Below I will explain how I got the Grid up and running.
Setup is pretty easy. All you have to do is download the Selenium Server standalone JAR file from http://selenium-release.storage.googleapis.com/index.html. You will have to install this file to all the machines that you will use as Hubs and Nodes. One quick note, you have to have JRE (Java Runtime Environment) setup on each machine you want to use as a Hub or Node.
If you have the JRE setup and on your system environment path, you can simply start the server with this command from the location of your Selenium Server standalone JAR file:
java -jar selenium-server-standalone-2.39.0.jar -port 4444 -role hub -nodeTimeout 600
I am using the 2.39.0 version of the server (make sure you use the correct name for your JAR file). This command starts the server on port 4444 with the Hub role and a timeout of 600 seconds. You can tuck this away in a bat file for easy access.
You can verify the hub is listening by viewing it in a browser. If you are on the hub machine, you can just go to localhost like so, http://localhost:4444/grid/console. This will present you with a page that you can view the configuration for the server.
To stop the Hub you just send it a command:
Having a Hub and no Node is just plain stupid. So, we need to add a Node to the Grid so that it can pass tests to it. The Hub will determine which Node to send a test to based on the properties requested by the test. So, we have to inform the Hub what properties the Node supports. There are a couple ways to do this, but I am going to use the command line to configure the Node. The way of the Ninja would be to use a JSON file, but I gave up on it after I couldn’t get it to recognize the JSON after about 30 minutes of research and trying. Actually, you can configure the Hub with JSON too, so you may want to look into this option as it makes your bat files cleaner and as you increase the Nodes you need it may cut down on duplication in your bat file too.
NOTE: If you are going to use IE or Chrome you should add the path to the drivers on your system path or you may see an error like:
*The path to the driver executable must be set by the webdriver.ie.driver system property; for more information, see http://code.google.com/p/selenium/wiki/InternetExplorerDriver. The latest version can be downloaded from http://selenium-release.storage.googleapis.com/index.html*
To start the node, run this command and don’t forget to run it in the path of your jar file and to update the file name/version appropriately.
java -jar selenium-server-standalone-2.39.0.jar -role webdriver -browser "browserName=internet explorer,version=8,maxinstance=1,platform=WINDOWS" -hubHost localhost –port 5555
This starts the Node and registers it on the Hub. You can also add this to a bat file. Again, you can verify it started by opening up the Grid console and you will see the Node browsers in the Browser tab, http://localhost:4444/grid/console
To run a test you have to use the RemoteDriver and pass it the DesiredCapabilities for the browser that tells the Hub what Node to use to satisfy the test.
DesiredCapabilities capabilities = new DesiredCapabilities.InternetExplorer(); capabilities.SetCapability(CapabilityType.Platform, "WINDOWS"); capabilities.SetCapability(CapabilityType.BrowserName, "internet explorer"); capabilities.SetCapability(CapabilityType.Version, "8"); IWebDriver webDriver = RemoteWebDriver(capabilities); Note: the code above is not best practice because it is not SOLID. If your test code isn't SOLID, you need to change your code to use a factory, IoC, or whatever you need to do to remove the dependence on concrete drivers and its supporting DesiredCapabilities. I will leave that as an exercise for you until I publish my framework code :).
This may be a big change to your tests as you would have to replace every place you use a concrete WebDriver to using the RemoteDriver. If you code for IWebDriver instead of a concrete driver and have a single point for the creation of WebDrivers (see note in code above), it wouldn’t be that bad as you are just adding another instance of IWebDriver.
Well that’s it. The biggest hurdle IMHO is just writing your code in a manner that makes it easy to to switch WebDriver instances. Now I have to figure out how to run tests in parallel, oh boy!
- The documentation for Grid is on the Selenium Wiki – https://code.google.com/p/selenium/wiki/Grid2
- I got a lot of good info from PacktPub.com – http://www.packtpub.com/sites/default/files/downloads/Distributed_Testing_with_Selenium_Grid.pdf
- Jon Austen provides some Windows batch scripts to start the Server and Node on his blog – http://thegreenoak.blogspot.com/2013/03/scripts-to-run-selenium-grid-hub-and.html