The user might have also easily defined his own layout for the summary file. In addition to executing the tests, the test bed serves as useful debugging platform. This is a significant feature when using independent testing teams, documenting the testing, etc. At test bed generation time the user can request that stubs are generated for some selected packages or subprograms. At test bed time the stubs are powerful means facilitating 'testing in isolation' and 'top-down testing'.
Stubs also make it possible to test more in the host computer.
The behavior of stub subprograms are determined as late as at test bed time. A stub can be 'interactive' allowing the user at the time of the call specify what values to return or what exception to raise. A stub can also be 'automatic' in which case the user has assigned for the stub a small script, which is executed each time the stub is called. If at some future point it is desired to replace some or all of the stubs with true application code. The corresponding true implementation code can simply be compiled and linked into the test bed.