fun afterScan(classes: List<KClass<out Spec>>): List<KClass<out Spec>>
Invoked as soon as the scan phase has completed. At this point, the Spec classes have been detected, but not yet instantiated or executed.
Overriding this function gives implementations the possibility of filtering the specs seen by the test engine.
For instance, a possible extension may filter tests by package name, class name, classes that only implement a certain interface, etc.
classes - the KClass for each discovered Spec
Return
the list of filtered classes to use.