Tutorials

Code Digging with Pex - Code Understanding and Automatic Testing At Your Fingertips (PDF) A step-by-step tutorial on applying Pex to any piece of code within Visual Studio.
Parameterized Unit Testing with Pex - Tutorial (PDF)
An 70+ pages tutorial that goes through the basics of unit testing, their extension to parameterized unit tests and more advanced topics on Pex.
Stubs And Moles - Tutorial (PDF) A step by step tutorial on using Stubs, Moles and Pex to test applications.
Unit Testing SharePoint Services with Pex (PDF) A step by step tutorial on writing isolated parameterized unit tests for SharePoint services using Pex.

Reference Manuals

Parameterized Test Patterns For Effective Testing with Pex - draft (PDF)
Coding patterns for authoring effective parameterized unit tests.
Extension Writer Handbook (PDF)
Guidance to create code that works well with Pex. This document is targetted for unit test framework and mock framework authors, or users willing to write extensions for Pex.
Online Reference Manual (also available as a single page)
Reference manual containing numerous details about the Pex infrastructure and APIs.
For Stubs/Moles documentation, visit http://research.microsoft.com/stubs.

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Pex Tutorial (tutorial on parameterized unit testing with Pex)
Samples used in Pex Tutorial
Pex Overview (an introduction with technical background)

Most of the documentation listed on this page is also bundled in the Pex installer.