The generated file is named "testout-ZF2new.pdf" not "testout-ZF2New.pdf"
which will make the test fail on case sensitive file systems as can be
found on many unix like systems.
so test for 'payment' being an instance of 'IZUGFeRDTradeSettlementDebit' as
'IZUGFeRDTradeSettlement' and 'IZUGFeRDTradeSettlementPayment' return 'null' for
'getPaymentXML()' which is not allowed to be written to the XML file.
or a NullPointerException might happen as 'hasDueDate==true' is not the result
of a test to ensure that 'trans' overwrites 'getDueDate()' at all, so the default
implementation from 'IZUGFeRDExportableTransaction' might get used which returns
the unusable result 'null'.
