private static void assertWatermarkFnNotEqual(WatermarkFunction watermarkFn, WatermarkFunction watermarkFn1) {
    if (watermarkFn == watermarkFn1 && watermarkFn == null) {
      return;
    }
    assertNotEquals(watermarkFn, watermarkFn1);
  }
Test util methods for {@link OperatorSpec} classes
samza-core/src/test/java/org/apache/samza/operators/spec/OperatorSpecTestUtils.java