The Problem:

You have an extensive suite of Geb functional tests running against Firefox and it takes a long time to run. You switch your tests over to PhantomJS; now they run twice as fast!

But five percent of the tests intermittently fail. After spending a few hours trying to figure it out, you still don’t know why they are failing — just that they fail sometimes, and you don’t want to spend the next week trying to figure out a workaround. As it stands, it’s not practical to switch to PhantomJS at this time.

A Solution:

Why not use both? Add the Poly Driver plugin to your project and configure it in GebConfig.groovy:

driver = {

   FirefoxDriver firefoxDriver = new FirefoxDriver()
   PhantomJSDriver phantomJSDriver = getPhantomDriver()

   new PolyDriver(mainDriver: phantomJSDriver, alternateDrivers: ['firefox' : firefoxDriver])
}

private PhantomJSDriver getPhantomDriver() {
   // see Tomás Lin’s excellent blog post on configuring drivers for Geb:
   // http://fbflex.wordpress.com/2013/03/18/how-to-configure-webdriver-in-grails-for-your-geb-tests/
}

Change the class inheritance of your problem test and annotate it:

class MyGebSpecCase extends GebReportingSpec {
  ...
}

becomes

import com.polydriver.spec.PolyDriverGebReportingSpec

@PreferredDriver('firefox')
class MyGebSpecCase extends PolyDriverGebReportingSpec {
  ...
}

When you run your tests, you will see a Firefox window open but only the FooGebSpecCase (and any others with the @PreferredDriver(‘firefox’) annotation) will use it. The rest of your tests will run quickly in PhantomJS.

The driver allows you to specify as many drivers as you want — you can even declare multiple instances of the same browser, so if you want to run a subset of tests against different Firefox profiles, you can do that:

driver = {
   FirefoxDriver firefoxDriver = new FirefoxDriver()
   FirefoxProfile ffProfile = new FirefoxProfile()
   // setup the other profile
   FirefoxDriver altFirefoxDriver = new FirefoxDriver(ffProfile)
   PhantomJSDriver phantomJSDriver = getPhantomDriver()

   new PolyDriver(
         mainDriver:       phantomJSDriver, 
         alternateDrivers: [
               'firefox':  firefoxDriver, 
               'ff-alt':   altFirefoxDrive
         ]
   )
}

Hopefully this eases the pain of transitioning your test suites to PhantomJS.