Testing with Pex

Some time ago I read about (might be on DotNetRocks) a little gem coming out of Microsoft’s research lab called Pex, which is a framework for doing automated White Box Testing in .Net. It’s still in its early days (despite having been around for more than 2 years now) but packs a bag of potential judging by what I’ve seen of the demo materials and been able to use myself!

In short, Pex is able to analyze your methods and work out the boundary conditions, etc. and derive a series of tests that can be used to test your method with as high a coverage as possible. The download package also includes a lightweight framework for test stubs and detours (which basically allows you to replace any .Net method with your own delegate) called Stubs and Moles. It also comes with the ability to automatically generate test project for you in MSTest and NUnit though I haven’t tested out the NUnit generation as it didn’t support NUnit generation the last time I played around it.

I won’t go into detail on how to use it as there are a ton of documentation and demo material on its site and I have barely scratched the surface myself, but do check it out if you haven’t done so already!

Liked this article? Support me on Patreon and get direct help from me via a private Slack channel or 1-2-1 mentoring.
Subscribe to my newsletter


Hi, I’m Yan. I’m an AWS Serverless Hero and the author of Production-Ready Serverless.

I specialise in rapidly transitioning teams to serverless and building production-ready services on AWS.

Are you struggling with serverless or need guidance on best practices? Do you want someone to review your architecture and help you avoid costly mistakes down the line? Whatever the case, I’m here to help.

Hire me.


Check out my new course, Complete Guide to AWS Step Functions. In this course, we’ll cover everything you need to know to use AWS Step Functions service effectively. Including basic concepts, HTTP and event triggers, activities, callbacks, nested workflows, design patterns and best practices.

Get Your Copy