@Override
  public boolean isAtEndOfCycle() {
    synchronized (LOCK) {
      return !iterator.hasNext();
    }
  }
Generates result values from an iterable object. If the iterator has no more
values left, the previous value is returned.

@author Peter Niederwieser
spock-core/src/main/java/org/spockframework/mock/response/IterableResponseGenerator.java