Java: Can't implement runnable on a test case: void run() collides

Question

So I have a test case that I want to make into a thread. I cannot extend Thread nor can I implement runnable since TestCase already has a method void run(). The compilation error I am getting is Error(62,17): method run() in class com.util.SeleneseTestCase cannot override method run() in class junit.framework.TestCase with different return type, was class junit.framework.TestResult.

What I am trying to do is to scale a Selenium testcase up to perform stress testing. I am not able to use selenium grid/pushtotest.com/amazon cloud at this time (installation issues/install time/resource issues). So this really is more of a Java language issue for me.

FYI: SeleniumTestCase is what I want to make multi threaded to scale it up for stress testing. SelniumTestCase extends TestCase (from junit). I am extending SeleniumTestCase and trying to make it implement Runnable.

Answer 1

In this case, you don't have other option: you have to delegate to another object instead of inheritance.

Answer 2

Create a inner class that implements Runnable and call it from a new Thread in com.util.SeleneseTestCase run() method. Something like this:

class YourTestCase extends SeleneseTestCase {
    public class MyRunnable implements Runnable {
        public void run() {
            // Do your have work here
        }
    }

    public void testMethodToExecuteInThread() {
        MyRunnable r = new MyRunnable();
        Thread t = new Thread(r);
        t.start();
    }
}

Update to use outside YourTestCase class

To run an inner class from another class you would need to make it public and then from the outer class execute this:

YourTestCase testCase = new YourTestCase();
YourTestCase.MyRunnable r = testCase.new MyRunnable();

But if you don't need to call it from inside your test case you'd better go with a normal class, make MyRunnable a public class without being in YourTestCase.

Hope it helps.

Answer 3

extending TestCase is almost certainly not the correct OO model anyhow. model with "has a" not "is a". that is, create a new class that extends thread, and use instances of that class within your test methods.

Answer 4

Keep in mind that if the thread throws any exceptions, the test would not necessarily fail. Instead of using Runnable and Thread, you might want to use ExecutorService.submit(Callable<T>):

public class SeleneseTestCase extends SeleniumTestCase {
  private class StressServer implements Callable<Void> {
    public Void call() {
      // do your work here
      return null;
    }
  }

  public void testUnderLoad() throws Exception {
    ExecutorService executorService = Executors.newFixedThreadPool(
        NUM_CONCURRENT_WORKERS);
    List<Callable<Void>> stressers = new ArrayList<Callable<Void>>();
    for (int i = 0; i < NUM_WORKERS; i++) }
      stressers.add(new StressServer());
    }
    List<Future<Void>> futures =if ( executorService.invokeAll(
        stressers, TIMEOUT_IN_SECS, TimeUnit.SECONDS);
    for (Future<Void> future : futures) {
      if (!future.isCancelled()) {
        future.get(1, TimeUnit.MILLISECONDS); // may throw exception
      }
    }
    executorService.shutdown();
  }
}

Note if you want the workers to return the result, you can change the type of StressServer to Callable<YourResultType>