Pax Exam how to start multiple containers

for a project i'm working on, we have the necessity to write PaxExam integration tests which run over multiple Karaf containers.

The idea would be finding a way to extend/configure PaxExam to start-up a Karaf container (or more) and deploying there a bounce of bundles, and then start the test Karaf container which will then test the functionality.

We need this to verify performance tests and other things.

Does someone know anything about that? Is that actually possible in PaxExam?

I write the answer by myself, after having found this interesting article.

In particular have a look at the sections Using the Karaf Shell and Distributed integration tests in Karaf

http://planet.jboss.org/post/advanced_integration_testing_with_pax_exam_karaf

This is basically what the article says:

first of all you have to change the test probe header, allowing the dynamic-package

@ProbeBuilder
public TestProbeBuilder probeConfiguration(TestProbeBuilder probe) {
    probe.setHeader(Constants.DYNAMICIMPORT_PACKAGE, "*;status=provisional");
    return probe;
}

After that, the article suggests the following code that is able to execute commands in the Karaf shell

@Inject 
CommandProcessor commandProcessor;

protected String executeCommands(final String ...commands) {
    String response;
    final ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
    final PrintStream printStream = new PrintStream(byteArrayOutputStream);
    final CommandSession commandSession = commandProcessor.createSession(System.in, printStream, System.err);
    FutureTask<string> commandFuture = new FutureTask<string>(
            new Callable<string>() {
                public String call() {
                    try {
                        for(String command:commands) {
                         System.err.println(command);
                         commandSession.execute(command);
                        }
                    } catch (Exception e) {
                        e.printStackTrace(System.err);
                    }
                    return byteArrayOutputStream.toString();
                }
            });

    try {
        executor.submit(commandFuture);
        response =  commandFuture.get(COMMAND_TIMEOUT, TimeUnit.MILLISECONDS);
    } catch (Exception e) {
        e.printStackTrace(System.err);
        response = "SHELL COMMAND TIMED OUT: ";
    }

    return response;
}

Then, the rest is kind of trivial, you will have to implement a layer able to start-up a child instance of Karaf

public void createInstances() {
    //Install broker feature that is provided by FuseESB
    executeCommands("admin:create --feature broker brokerChildInstance");
    //Install producer feature that provided by imaginary feature repo.
    executeCommands("admin:create --featureURL mvn:imaginary/repo/1.0/xml/features --feature producer producerChildInstance");
    //Install producer feature that provided by imaginary feature repo.
    executeCommands("admin:create --featureURL mvn:imaginary/repo/1.0/xml/features --feature consumer consumerChildInstance");

    //start child instances
    executeCommands("admin:start brokerChildInstance");
    executeCommands("admin:start producerChildInstance");
    executeCommands("admin:start consumerChildInstance");

    //You will need to destroy the child instances once you are done.
    //Using @After seems the right place to do that.
}