### Question:
DummyVariableCreator extends AbstractDatasetFeatureVectorTransformer implements Serializable { public FeatureVector convert(FeatureVector featureVector) { Validate.notNull(featureVector, "featureVector must not be null"); if (mappers.isEmpty()) { return featureVector; } List<FeatureVector> appendedVectors = new ArrayList<>(); if (keepOriginalFeature) { appendedVectors.add(featureVector); } else { appendedVectors.add(new FilteredVector(featureVector, not(equal(mappers.keySet())))); } for (VectorEntry<String, Value> entry : featureVector) { String featureName = entry.key(); Value featureValue = entry.value(); Mapper mapper = mappers.get(featureName); if (mapper != null) { appendedVectors.add(mapper.getAppendedFeatureVector(featureValue)); } } return new AppendedVector(appendedVectors); } @Deprecated  DummyVariableCreator(Dataset dataset); @Deprecated  DummyVariableCreator(Dataset dataset, boolean keepOriginalFeature);  DummyVariableCreator(Dataset dataset, boolean keepOriginalFeature, boolean dense); @Override FeatureInformation getFeatureInformation(FeatureInformation featureInformation); @Override FeatureVector apply(FeatureVector featureVector); FeatureVector convert(FeatureVector featureVector); @Override String toString();  }### Answer:
@SuppressWarnings("deprecation") @Test public void testNullValueHandling() { Dataset dataset = makeDataset(); DummyVariableCreator dummyVariableCreator = new DummyVariableCreator(dataset); FeatureVector instance = new InstanceBuilder().set("f1", NullValue.NULL).create(); FeatureVector converted = dummyVariableCreator.convert(instance); assertEquals(0, converted.getNumeric("f1:alpha").getInt()); assertEquals(0, converted.getNumeric("f1:beta").getInt()); assertEquals(0, converted.getNumeric("f1:gamma").getInt()); assertEquals(0, converted.getNumeric("f1:delta").getInt()); }