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Running Tests on Multiple Browsers in a Grid

A distributed test environment ("Test grid") consists of a hub and a number of test nodes. The hub acts as an orchestrator, tracking what browsers are available in the nodes and making sure that a node is only used by one test at a time. The nodes have one or several browsers installed and a node is where the actual test is executed.

When running a test on a hub, the TestBench test asks the hub for a certain browser (based on a list of capabilities) instead of launching a local browser. The hub waits until a suitable browser is available on some node, reserves that and redirects the test to that given node. The test is then executed and after it has finished, the node reservation is removed and the node used for another test.

When running on a hub, you do not need a local webdriver installed. The webdriver must be installed on the node instead.

Preparing your Tests for Running on a Test Grid

The tests created previously are setup only to run on a single browser, as a single ChromeDriver (or other WebDriver) instance is created in a @Before method. When running on multiple browsers in parallel, it’s easier not to handle the driver instances manually but instead let TestBench handle creation and destruction when needed. To do this, you need to:

  1. Extend ParallelTest instead of TestBenchTestCase. The ParallelTest class takes care of creating and destroying driver instances as needed.

  2. Define the grid hub URL using either

    1. @RunOnHub("") on the test class (or a super class) or the system property com.vaadin.testbench.Parameters.hubHostname

    2. Configure Sauce Labs credentials and use Sauce Connect proxy to use Sauce Labs test grid. See Using Sauce Labs Test Grid

A test class extending ParallelTest will automatically:

  • Execute test methods in parallel on the hub defined using @RunOnHub or the corresponding system property

  • Create a suitable webdriver instance

  • Terminate the driver after the test ends

  • Grab a screenshot if the test fails

  • Support running the test locally on only one browser for debugging, using @RunLocally or the corresponding system property

When changing the super class of the test, you need to remove any calls to setDriver(new ChromeDriver()) or similar, and also any @After method which does getDriver().quit().
In almost all cases you want to configure something for all your grid tests so it makes sense to create a common superclass, e.g. public abstract class AbstractIT extends ParallelTest. Then you can add a @RunOnHub annotation on that class.
Up to 50 test methods in any ParallelTest class will be executed simultaneously by default. The limit can be set using the com.vaadin.testbench.Parameters.testsInParallel system property. If your tests do not work in parallel set the parameter to 1.
When running tests in parallel, you need to ensure that the tests are independent and do not affect each other in any way.
You can handle creation and destruction of the webdriver manually also when running on a hub if you do not want to use ParallelTest for one reason or another. In this case you should create a RemoteWebdriver with the correct hub URL and set suitable DesiredCapabilities on the driver.

Using Sauce Labs Test Grid

To run your tests on Sauce Labs you first need to get an account at and take note of your user name and access key.

Before starting a test, you need to set up the Sauce Connect proxy. The proxy creates a secure connection between the Sauce Labs browser environment and your machine, so the Sauce Labs browsers can access a server you are running locally. You should run the proxy with a tunnel identifier (-i some-tunnel-identifier) to avoid conflicts with other tunnels that you or a CI server might create later.

When the proxy is up and running, you can run your tests by passing the Sauce Labs username and access key to it. This can be done using system properties, e.g.

mvn verify -Dsauce.user=<yourusername> -Dsauce.sauceAccessKey=<youraccesskey> -Dsauce.tunnelId=some-tunnel-identifier

or by first setting the credentials as environment variables and then running the tests, e.g.

export SAUCE_USERNAME=<yourusername>
export SAUCE_ACCESS_KEY=<youraccesskey>
export SAUCE_TUNNEL_ID=some-tunnel-identifier
mvn verify

When writing your tests, there is nothing special about Sauce Labs that needs to be taken into account. You write them as described in Preparing your Tests for Running on a Test Grid

When running tests on a CI/build server, you typically have a build step before the tests, where the Sauce Connect Proxy is started, and a build step after the tests, where the tunnel is torn down.

Defining the Browsers to Run Tests On

You can define the tested browsers and their versions in an environment variable TESTBENCH_GRID_BROWSERS or system property com.vaadin.testbench.Parameters.gridBrowsers with a comma separated list e.g. -Dcom.vaadin.testbench.Parameters.gridBrowsers=chrome,firefox,safari-11,safari-9.

If you don’t want to use the environment variable, you can define the configuration in your test class, in a method annotated with @BrowserConfiguration. It returns a list of DesiredCapabilities, typically describing what platform, os and browser name/version should be used. Typically this is defined in a superclass for the test so that all tests are run on the same browsers, e.g.

public abstract class AbstractIT extends ParallelTest {

   public List<DesiredCapabilities> getBrowserConfiguration() {
       List<DesiredCapabilities> browsers =
           new ArrayList<DesiredCapabilities>();

       // Add all the browsers you want to test

       return browsers;
The BrowserUtil helper methods create a DesiredCapability object which works in many cases. To customize the versions and other values, annotate your test class using @BrowserFactory(MyBrowserFactory.class) and implement MyBrowserFactory by extending DefaultBrowserFactory.
To run a multi browser test locally, you can use the com.vaadin.testbench.Parameters.runLocally system property (or a @RunLocally annotation on the test class) to override what browser to run on. The value of the property or annotation should be the browser to run on, e.g. chrome or @RunLocally(Browser.CHROME). When RunLocally is used, any hub configuration is also ignored and a local webdriver is used.