Pex – Assisted White Box Testing

On a brief side note after attending Mitch Denny’s (from Readify) presentation tonight on “Tools for Improving Software Quality” he introduced us to a great little tool for Visual Studio 2008 and beyond. “Pex (Program EXploration) produces a traditional unit test suite with high code coverage“.

It’s a tool that writes the unit test for you!

This may seem like a contradiction to the purpose of the unit test, and slap in the face for those promoting Test Driven Development (TDD). But that’s incorrect. The purpose of Pex is to assist in catching the missed branches (especially the mundane and tedious ones from switch statements). To be used to polish the unit tests, after the best practice approach is followed; of writing the core of the unit test before coding the actual function begins.

Given a parameterized unit test written in a .NET language, Pex automatically produces a small unit test suite with high code and assertion coverage. To do so, Pex performs a systematic white box program analysis.

Download it here at the Research.Microsoft.com site; available for “Commercial Evaluation” and “Academic Use” as it’s still in Beta.

The tool integrates directly into Visual Studio and assist with MSTest tests. You write click on a method and it explores the code paths determines input variables to test areas of the code your logic currently doesn’t cater for, thereby allowing you to further expand the function itself to cater for more “expected exceptions”.runpex

Here are some more screen shots on the official Pex site, also check out the Channel 9 video on it.

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