1. An isolation system, implemented by electrical processing functionality, for processing product code so that the product code can be tested without dependency on external functionality, comprising: logic configured to receive original product code, the product code containing a plurality of original methods, at least one original method being dependent on external functionality that is not under control of a test being performed; logic configured to receive selection information which defines a subset of original methods to be processed; and logic configured to convert each original method in the subset of original methods into a corresponding modified part, the modified part declaring a type-safe property having a delegate type.