Run in multiple threads for tests

RunInThreads.java

import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

/**
 * Run in multiple threads.
 */
public class RunInThreads {

  private final int numberOfThreads;

  public RunInThreads(int numberOfThreads) {
    this.numberOfThreads = numberOfThreads;
  }

  public void run(Runnable runnable) throws InterruptedException {
    CountDownLatch countDownLatch = new CountDownLatch(numberOfThreads);
    ExecutorService executorService = Executors.newFixedThreadPool(numberOfThreads);
    for (long i = 1; i <= numberOfThreads; i++) {
      executorService.execute(() -> {
        runnable.run();
        countDownLatch.countDown();
      });
    }
    countDownLatch.await();
    executorService.shutdown();
  }

}