A test, a WebDriver and a browser in Selenium's world

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There are a couple of ways to design how to work with a real browser while execution automated tests implemented with Selenium. Suppose, we need to use Mozilla Firefox browser to run a WEB test. The most probable way is to initiate an instance of a FirefoxDriver and play with it. Looks very easy, isn’t? Is it the best way?

Selenium offers two ways of interacting with a browser:

  • using a browser-specific implementation - FirefoxDriver for Mozilla Firefox (ChromeDriver for Google Chrome etc.)
  • using an universal implementation - RemoteWebDriver

Let’s use mentioned above Java implementations. However, you can apply the info to a language you are working with as Selenium works in the same way everywhere.

What is a significant difference between these methods?

The FirefoxDriver runs appropriate WebDriver (GeckoDriver) server (aka process) and sends Selenium commands to it. The GeckoDriver server is going to execute them in an browser window. This means the tests are responsible for preparation of an infrastructure for testing each time you create an instance of FirefoxDriver.

And it works excellent on a single local environment. Once the tests are moved to some another environment, it may stop to work. And there are several reasons for it:

  • a GeckoDriver is not available in the PATH
  • a path for GeckoDriver is wrong (webdriver.firefox.driver property)
  • a version of GeckoDriver is not compatible with a Mozilla Firefox

The RemoteWebDriver just connects to already started WebDriver server and sends Selenium commands to it. This means the tests aren’t responsible for an infrastructure. The infrastructure (browsers and webdrivers) has to be ready for tests. It means either WebDriver server or Selenium Hub has to be run before the tests execution. And the tests only send Selenium commands to a specific server which can be found by given URL. That’s all!

The RemoteWebDriver supports Selenium Hub URL (http://localhost:4444/wd/hub) as well as started the GeckoDriver executable (http://localhost:4444).

So, instead of new FirefoxDriver() use

WebDriver driver = new RemoteWebDriver(
        new URL(System.getProperty("ff-url", "http://localhost:4444")), 
        DesiredCapabilities.firefox()
);

Conclusion

Keep things separated. A preparation of an infrastructure for testing is a task. An execution of Selenium tests is another one.

Do you want to automate them both? This is one more task which has to be implemented properly. Using new FirefoxDriver() is not a proper implementation, is it?

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