BEHAT_SCREEN_SIZE env var

README.md

@@ -280,6 +280,15 @@ Example: mymodule/tests/behat/features/bootstrap/MyModule/Test/Behaviour/Feature
 	    }
 	}
 
+### Screen Size
+
+In some Selenium drivers like [SauceLabs](http://www.saucelabs.com) you can 
+define the desired browser window size through a `capabilities` definition.
+By default, Selenium doesn't support this though, so we've added a workaround
+through an environment variable:
+
+	BEHAT_SCREEN_SIZE=320x600 vendor/bin/behat
+
 ## FAQ
 
 ### FeatureContext not found

src/SilverStripe/BehatExtension/Context/SilverStripeContext.php

@@ -131,6 +131,11 @@ class SilverStripeContext extends MinkContext implements SilverStripeAwareContex
 		}
 
 		$this->testSessionEnvironment->startTestSession($this->getTestSessionState());
+
+		if($screenSize = getenv('BEHAT_SCREEN_SIZE')) {
+			list($screenWidth, $screenHeight) = explode('x', $screenSize);
+			$this->getSession()->resizeWindow((int)$screenWidth, (int)$screenHeight);
+		}
 	}
 
 	/**