@Test
public void testSendOutstanding() {

  final AtomicInteger callableCounter = new AtomicInteger();
  underTest =
      new BatcherImpl<>(
          SQUARER_BATCHING_DESC_V2,
          new LabeledIntSquarerCallable() {
            @Override
            public ApiFuture<List<Integer>> futureCall(LabeledIntList request) {
              callableCounter.incrementAndGet();
              return super.futureCall(request);
            }
          },
          labeledIntList,
          batchingSettings,
          EXECUTOR);
  // Empty Batcher
  underTest.sendOutstanding();
  assertThat(callableCounter.get()).isEqualTo(0);
  underTest.add(2);
  underTest.add(3);
  underTest.add(4);
  underTest.sendOutstanding();
  assertThat(callableCounter.get()).isEqualTo(1);
}