Arise, awake, and learn by approaching the exalted ones,
for that path is sharp as a razor’s edge, impassable,
and hard to go by, say the wise.
Because every single reason has the same, if not more, number of reasons to be wrong!
It seems that many have found NUnit 2.5.5 not working with DLLs compiled with .net 4.0. NUnit 3.x has been designated to work with .net 4.0; till that time make a modification to the NUnit config file and add this startup element under the main configuration element :