### Question:
AbstractNoStoreAggregator extends AbstractTimedAggregator<T> { @Override protected int retrieveDataSize() { return 0; } AbstractNoStoreAggregator(BinaryFunction<T, T, T> aggregationFunction);  AbstractNoStoreAggregator(BinaryFunction<T, T, T> aggregationFunction, long interval);  AbstractNoStoreAggregator(BinaryFunction<T, T, T> aggregationFunction, long interval,
            boolean useSharedTimer); @Override String toString();  }### Answer:
@Test public void testDataSize() { assertEquals(0, new TestNoStoreAggregator<Object>(new Object()).retrieveDataSize()); }