Mighty-Moose now free of charge.
Phil Haack (best known as ex Microsoft and NuGet leader, now at GitHub) shared an alternative and clever way to organize test classes, using a nested class for every method of parent class: Structuring Unit Tests.
Then look at some tweaks here Zen Coding: Structuring Unit Tests, especially about avoid duplication of code when you need to setup the main class.
Software testing antipatterns… pay attention!
7 Deadly Sins of Automated Software Testing « Adrian Smith.