The second idea just involves making a normal DBUnit XML dataset file
(see http://www.dbunit.org/components.html#FlatXmlDataSet) and then
copying the XML for the user data to the end and modifying it by hand
(or search & replace). If you use a REFRESH operation then DBUnit will
insert data if it's not already there (based on the primary key of the
database table) or update the row if the primary key already exists.