more tests, plus consistency in naming the tests (using the XML datatype
as name and adding Test)
if types are primitive, they don't have XmlElement annotations, they are
not optional, not nullable, they should be marked as required in the
ApiProperty
more tests, to check the Wrapper versions of primitives when
minOccurs="0"
more tests, to check the Wrapper versions of primitives and others when
minOccurs="0"
required = false