public static Combine.CombineFn<Boolean, ?, Long> combineFn() {
    return new CountIfFn();
  }
@Test
  public void testExtractsOutput() {
    Combine.CombineFn countIfFn = CountIf.combineFn();

    assertEquals(0L, countIfFn.extractOutput(countIfFn.createAccumulator()));
  }