package org.slf4j.testHarness;
   
   import static org.junit.Assert.assertTrue;
   import static org.junit.Assert.fail;
   
   import java.util.ArrayList;
   import java.util.Collections;
   import java.util.List;
   import java.util.concurrent.BrokenBarrierException;
  import java.util.concurrent.CyclicBarrier;
  import java.util.concurrent.atomic.AtomicLong;
  
  import org.junit.Test;
  import org.slf4j.Logger;
  import org.slf4j.LoggerAccessingThread;
  import org.slf4j.LoggerFactory;
  import org.slf4j.event.EventRecordingLogger;
  import org.slf4j.helpers.SubstituteLogger;
  
  abstract public class MultithreadedInitializationTest {
      final protected static int THREAD_COUNT = 4 + Runtime.getRuntime().availableProcessors() * 2;
  
      private final List<Logger> createdLoggers = Collections.synchronizedList(new ArrayList<>());
  
      final protected AtomicLong eventCount = new AtomicLong(0);
      final private CyclicBarrier barrier = new CyclicBarrier(THREAD_COUNT + 1);
  
      @Test
      public void multiThreadedInitialization() throws InterruptedException, BrokenBarrierException {
          @SuppressWarnings("unused")
          LoggerAccessingThread[] accessors = harness();
  
          Logger logger = LoggerFactory.getLogger(getClass().getName());
          logger.info("hello");
          eventCount.getAndIncrement();
  
          assertAllSubstLoggersAreFixed();
          long recordedEventCount = getRecordedEventCount();
          int LENIENCY_COUNT = 21;
  
          long expectedEventCount = eventCount.get() + extraLogEvents();
  
          assertTrue(expectedEventCount + " >= " + recordedEventCount, expectedEventCount >= recordedEventCount);
          assertTrue(expectedEventCount + " < " + recordedEventCount + "+" + LENIENCY_COUNT, expectedEventCount < recordedEventCount + LENIENCY_COUNT);
      }
  
      abstract protected long getRecordedEventCount();
  
      protected int extraLogEvents() {
          return 0;
      }
  
      private void assertAllSubstLoggersAreFixed() {
          for (Logger logger : createdLoggers) {
              if (logger instanceof SubstituteLogger) {
                  SubstituteLogger substLogger = (SubstituteLogger) logger;
                  if (substLogger.delegate() instanceof EventRecordingLogger)
                      fail("substLogger " + substLogger.getName() + " has a delegate of type EventRecodingLogger");
              }
          }
      }
  
      private LoggerAccessingThread[] harness() throws InterruptedException, BrokenBarrierException {
          LoggerAccessingThread[] threads = new LoggerAccessingThread[THREAD_COUNT];
          for (int i = 0; i < THREAD_COUNT; i++) {
              threads[i] = new LoggerAccessingThread(barrier, createdLoggers, i, eventCount);
              threads[i].start();
          }
  
          // trigger barrier
          barrier.await();
  
          for (int i = 0; i < THREAD_COUNT; i++) {
              threads[i].join();
          }
  
          return threads;
      }
  }