Show HN: CrossHair – SMT Assisted Testing for Python

[ZeroCool2u]

Hey there, this project looks really great! There seems to be some overlap with the Hypothesis-Auto[1] project. Have you looked into collaborating with Tim and perhaps merging your work together? It seems like it would be very powerful!

[1] https://timothycrosley.github.io/hypothesis-auto/

[timothycrosley]

Can confirm that I would be happy to collaborate on this project, it looks really cool!

[pschanely]

Hi all! My primary objective with this post is to find potential collaborators and people willing to try it. (and file bugs!)

If you do try it, I'd encourage you to think of it as an exercise in formally documenting your code's behavior, with the side benefit that CrossHair can sometimes help you ensure the correctness of that documentation.

And, of course, feedback of any kind at all is honestly appreciated. Thanks for being the awesome community that you are!

[zitterbewegung]

This is a really minor nitpick that I am expressing to help you market this better. Instead of saying (defunct) PEP 316 just say inspired which communicates that you don’t do everything of pep 316 also .

[exdsq]

Hey! I'd love to collaborate :)

This is an area I'm trying to focus my Masters on, so any opportunity to apply what I'm reading is more than welcome! I'll add my email to my profile if you'd like to chat.

[philzook]

Very cool! Ever looked at the Viper project? It's the only other system in python that I know of targeting pre and post conditions

https://www.pm.inf.ethz.ch/research/viper.html

https://www.pm.inf.ethz.ch/research/nagini.html

Another thing that might be of interest is HOLpy. I have no idea what the state of that is. https://arxiv.org/abs/1905.05970

I was fiddling around recently with way jankier methods than what you've done here http://www.philipzucker.com/programming-and-interactive-prov...

[typon]

This looks really cool. Love to see z3 being used for tools.

[pschanely]

Yes. Z3 is impressive. I intend to do a write-up of how I chose to model Python values in it soon.

[im_down_w_otp]

So this is Symbolic Execution based testing for Python?

[pschanely]

That's right! We pick different choose execution paths arbitrarily and accumulate constraints in an SMT solver as we go. It's implemented with special objects that look just like ints, strings, etc; this might help:

https://twitter.com/pschanely/status/1176151748844691456