### Question:
IndexSamplingJobQueue { public synchronized T poll() { return queue.poll(); } IndexSamplingJobQueue( Predicate<? super T> enqueueablePredicate ); synchronized void add( boolean force, T item ); synchronized void addAll( boolean force, Iterator<T> items ); synchronized T poll(); synchronized Iterable<T> pollAll();  }### Answer:
@Test public void returnsNullWhenEmpty() { assertNull( new IndexSamplingJobQueue<>( Predicates.alwaysTrue() ).poll() ); }