Pattern to make a third party library more testable

Hi

I am working with a third party library that used a sealed class for its main class. This class also requires concreate implementations of one of its other clases that are passed in as method parameters.

Just wondered if anyone could offer some ideas on what sort of patter to put this into. I have coded it at the moment as a Facade as I am only publicly offering some of the functionality. My main issue is though that I need to "new up" the dependencies within the facade so a true unit test isn't possible.... I don't think that there is away around this but thought I'd put the question out there.

Cheers