@Nonnull
  @Override
  public Sketch getResult() {
    return unionAll();
  }
@Test
  public void testThresholdBehavior() {
    UpdateSketch input1 = Sketches.updateSketchBuilder().build();
    IntStream.range(0, 1000).forEach(input1::update);
    Sketch sketch1 = input1.compact();
    UpdateSketch input2 = Sketches.updateSketchBuilder().build();
    IntStream.range(1000, 2000).forEach(input2::update);
    Sketch sketch2 = input2.compact();

    ThetaSketchAccumulator accumulator = new ThetaSketchAccumulator(_setOperationBuilder, 3);
    accumulator.apply(sketch1);
    accumulator.apply(sketch2);

    Assert.assertEquals(accumulator.getResult().getEstimate(), sketch1.getEstimate() + sketch2.getEstimate());
  }