mocked DBI interface for testing purposes

 Test::MockDBI has a major advantage over DBI::trace()
 or DBD::Mock -- Test::MockDBI lets you change how the
 mocked DBI functions behave, along with modifying
 what data is returned by the mocked DBI functions.
 These changes and modifications can be made specific
 to particular SQL statement patterns.
 .
 This ability to modify DBI function behavior and
 DBI-returned data makes it easier to test code that has
 different branches for different DBI behaviors -- you
 can test that a failure within DBI or returned DB data
 that is different than normal is processed correctly by
 your module or program. If you are taking over a large
 code base, Test::MockDBI will help in understanding the
 code by allowing you to safely check how the code behaves
 under different database conditions without modifying any
 databases (production or otherwise).