# Introducing Model\_quickcheck. Quickcheck for stateful, imperative code

**URL:** <https://discuss.ocaml.org/t/introducing-model-quickcheck-quickcheck-for-stateful-imperative-code/5301>\
**Category:** Learning\
**Created:** [March 12, 2020, 1:57am UTC](https://discuss.ocaml.org/t/introducing-model-quickcheck-quickcheck-for-stateful-imperative-code/5301 "2020-03-12T01:57:06Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![suttonshire](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/suttonshire/32/2045_2.png) [@suttonshire](https://discuss.ocaml.org/u/suttonshire)\
**Post date:** [March 12, 2020, 1:57am UTC](https://discuss.ocaml.org/t/introducing-model-quickcheck-quickcheck-for-stateful-imperative-code/5301/1 "2020-03-12T01:57:06Z")

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Hi there!

I’m sharing a small project I’ve been working on that I hope will be interesting or useful to the community. [Model\_quickcheck](https://github.com/suttonshire/model_quickcheck) is a model-based testing system that allows you to validate the “properties” of stateful, imperative OCaml programs. It’s built on Jane Street’s Base\_quickcheck. I’d love to read your thoughts.

I just started learning OCaml and one of the first projects I’ve been working on is a user-space reliable transport protocol. Writing tests for this system became unwieldy because I was trying to validate certain properties of the protocol by thinking up very specific sequences of actions that would invoke behaviors that relied on that property. I got tired of it and got curious if there was a way to generate these interesting sequences. My research turned up frameworks like QCSTM[0] and PropEr[1] for state machine property-based testing. This seemed to be exactly what I needed so I started building something similar.

To use Model\_quickcheck you specify a set of actions to apply to your program, a model that describes the state of you program and a set of predicates that define the properties of you system. The model is hopefully a simpler representation of your system e.g. a map instead of a key-value database, or a queue instead of a reliable network protocol. Model\_quickcheck then generates a random sequences of actions applies them to your system and verifies the properties.

This has been an exciting and useful project. I’ve learned a bunch about the Base library, Quickcheck, first class modules, and inline tests. I’m just getting started, but I just wanted to share the project with the community since I’ve learned a lot by lurking here.

[0] ~https://github.com/jmid/qcstm~  
[1] ~https://propertesting.com/book\_state\_machine\_properties.html~