if (useBarriers) {
        firstBarrier.await();
        secondBarrier.await();
      }
    }

    @Override
    protected ScheduledExecutorService executor() {
      // use a bunch of threads so that weird overlapping schedules are more likely to happen.
      return Executors.newScheduledThreadPool(10);
    }

    @Override
    protected Scheduler scheduler() {

    }
  }

  interface Receiver<T> {
    void accept(@Nullable T object);
  }

  /**
   * Assuming the given cache has maximum size {@code maxSize}, this method populates the cache (by
   * getting a bunch of different keys), then makes sure all the items in the cache are also in the
   * eviction queue. It will invoke the given {@code operation} on the first element in the eviction

  }

  @J2ktIncompatible
  @GwtIncompatible // NullPointerTester
  public void testNullPointers() {
    /*
     * Don't bother testing: Preconditions defines a bunch of methods that accept a template (or
     * even entire message) that simultaneously:
     *
     * - _shouldn't_ be null, so we don't annotate it with @Nullable
     *

import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.atomic.AtomicInteger;
import junit.framework.TestCase;

/**
 * Basher test for {@link ConcurrentHashMultiset}: start a bunch of threads, have each of them do
 * operations at random. Each thread keeps track of the per-key deltas that it's directly
 * responsible for; after all threads have completed, we sum the per-key deltas and compare to the

            TimeUnit.SECONDS,
            new ArrayBlockingQueue<Runnable>(1000));
    executorService.prestartAllCoreThreads();
    final AtomicInteger integer = new AtomicInteger();
    // Execute a bunch of tasks to ensure that our threads are allocated and hot
    for (int i = 0; i < NUM_THREADS * 10; i++) {
      @SuppressWarnings("unused") // https://errorprone.info/bugpattern/FutureReturnValueIgnored

    assertEquals("a", notification.getValue());
    assertEquals(1, cache.size());
    assertEquals("b", cache.getUnchecked("b"));
  }

  // "Basher tests", where we throw a bunch of stuff at a LoadingCache and check basic invariants.

  /**
   * This is a less carefully-controlled version of {@link #testRemovalNotification_clear} - this is