### Question:
NullValueSerializer extends NonTypedScalarSerializerBase<UberNode.NullValue> { @Override public void serialize(UberNode.NullValue value, JsonGenerator jgen, SerializerProvider provider) throws IOException, JsonGenerationException { jgen.writeNull(); } protected  NullValueSerializer(); @Override void serialize(UberNode.NullValue value, JsonGenerator jgen, SerializerProvider provider);  }### Answer:
@Test public void serializesNullValue() throws Exception { nullValueSerializer.serialize(UberNode.NULL_VALUE, jgen, serializerProvider); Mockito.verify(jgen) .writeNull(); }