Drupal + Simpletest + Class Autoloading = FALSE?
I assumed that all "autoloadable" files for the module I was testing would indeed be automatically loaded, but this seemed to be wrong.

I needed to add the following function to my testclass:

public function setUp() {
  parent::setUp('mta');
}


Please note that 'mta' is the module I'm testing, and which the "autoloadable" classes are defined for. I assume that if you need access to "autoloadable" classes defined for any other module, that you need to set up those modules too.