fun clearAllEvents() {
    while (eventSequence.isNotEmpty()) {
      takeEvent()
    }
  }

  private fun logEvent(e: CallEvent) {
    for (lock in forbiddenLocks) {
      assertThat(Thread.holdsLock(lock), lock.toString()).isFalse()
    }

    if (enforceOrder) {
      checkForStartEvent(e)
    }

    eventSequence.offer(e)
  }

  private fun checkForStartEvent(e: CallEvent) {

        throws ExecutionException {
      if (!valueReference.isLoading()) {
        throw new AssertionError();
      }

      checkState(!Thread.holdsLock(e), "Recursive load of: %s", key);
      // don't consider expiration as we're concurrent with loading
      try {
        V value = valueReference.waitForValue();
        if (value == null) {