Research: Contract Checking and Automated Test Generation with Pex

Play Research: Contract Checking and Automated Test Generation with Pex

The Discussion

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    Mike mentions that the current design by contract features are available for download under the research license. Where can I find that download?
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    Great stuff!

    I must admit I was saddened to hear Spec# wouldn't be integrated into C# 4. But this is the next best thing; I'm glad to see design-by-contract getting some attention in the .NET framework itself.

    If I may comment on the presentation, it feels like you both should have had your own presentations. It felt too rushed and too crammed.

    Having Mike go deeper into the evolution of Spec# and why they chose a library instead of C# langauge integration would've been great. And Nikolai covering more real-world unit testing scenarios with Pex - for example, testing code with dependencies like the file system or UI using Pex, would have been a great presentation by itself.

     Also, the rehearsed Q&A between Mike and Nikolai was cheesy. Too tongue-in-cheek! Smiley

    Beyond that, great stuff guys! I'm really happy to see DbC getting some real attention, I believe it will help us write code that more clearly expresses our intent and contains fewer bugs. That's something every developer can get behind. Going to go download and play with the VS2008-integration...

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    After playing with the library for awhile, I think this has a lot of potentials.

    I'd like to give you guys some feedback as I considered how we would integrate this stuff into our codebase (that is, once contracts are under a commercial-friendly license!). Where do we send feedback?
  • User profile image
    Hi Judah, you can send feedback to


    Justin Van Patten
    Program Manager
    Common Language Runtime
  • User profile image
    The presentation was great and I love Pex and the contract stuff, but when are we going to get a license on it so that I can use it in vs2008 for the projects I am developing commerically, instead of just and academic license?
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    Agreed....Your Pex talk was one of the favorite I attended at PDC (despite the cheesy scripted dialogue - I didn't mind it  Smiley .  You guys did great breaking it down for people new to Design by Contract such as myself.

    But until this stuff is released under a non-research license, I just can't feel like I can use it and invest any time into it

    But great talk, great work on the technology...these are the things that excite me about where Microsoft is going
  • User profile image
    Thanks for all the great comments! I'm glad you pointed out our limitations as comedians: Nikolai and I had been just about to quit our day jobs and head back to LA to make our names in the comedy clubs there. I guess we'll just have to stay at MSR and work on Contracts and Pex!

    I just wanted to point out that we have a web site for the project: That page contains a link to an email alias we've set up: codconfb _at_ microsoft _dot_ com. You can use that to send specific comments about the tools and the many bugs I'm sure you'll find in our tools. The alias is unfortunately one-way. We can see the mail you send to it, but you can't join the alias. We are working on a separate forum for the Code Contracts project, but it isn't set up yet.

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    In the talk you mention that you do IL-weaving to inject the right code for the contracts. Is this IL reader/writer something that can be used separately from Contracts? I've been using Cecil ( for some R&D stuff and it would be awesome if there was something like this somewhere from Microsoft Smiley.

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    Pex is now available for Visual Studio 2008 under the pre-release license. Check it out at .

  • User profile image
    CCI (the framework used to rewrite the assemblies) was released as open source on codeplex at

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