What is the major difference between Pex vs MsTest?

Question

What is the major difference between Pex vs MsTest? when to use what?

Answer 1

My Impression is that Pex is a supplement to traditional testing frameworks like MSTest or NUnit, rather than a competing framework. Threads like this one: Is Pex (Test generation) really useful tool? seem to indicate that Pex aids in creating parametrized unit tests driven by data, and in generating tests based on assertions in the tests themselves, but can be used with a variety of frameworks.