Question about testing subclasses of Module::Build

I am writing a subclass of Module::Build but I am hitting a few issues 
with the test scripts. The current problem is that I need to take the 
'pm' file from the 't/lib' directory rather than the 'lib' directory but 
only for testing purposes. Looking at the test scripts in Module::Build, 
I can see that it needs to address much the same issues. Rather than all 
subclassers having to reinvent the wheel surely there is a desperate 
need to have these as public documented modules.