I have a bunch of classes that are designed to basically test some parameters and tell me if the thing they represent is complete or not yet. For example the "DownloadTester" will be passed a filename and size will check if the file exists and is the given size, and the "EmailTester" will take an email address and subject and check if such an email has been received etc.

I'd like to have a generic constructor that takes an array of parameters so I can do this in a plug-in manner. What is the best way of doing this given an interface cannot specify anything about a class constructor?