# What is Crux?

Crux is a tool for improving the assurance of software using **symbolic testing**, currently supporting C/C++ and Rust. Crux can provide you with additional assurance that your code does what you want it to do, and provides higher coverage of possible inputs than techniques such as randomized fuzzing or unit testing.

Specifically, Crux uses symbolic reasoning to check tests **exhaustively**, on all possible inputs, rather than on a smaller number of fixed or randomly-chosen values. In this way, Crux improves the coverage possible with [property-based testing](https://www.drmaciver.com/2016/03/the-easy-way-to-get-started-with-property-based-testing/), a popular approach supported by [libraries](https://github.com/silentbicycle/theft) [for](https://en.wikipedia.org/wiki/QuickCheck) [many](https://blog.logrocket.com/property-based-testing-in-rust-with-proptest/) [languages](https://jsverify.github.io/).

Crux can:

* Perform **symbolic** reasoning to evaluate tests **exhaustively**
* Analyze **C/C++** and **Rust** code
* Generate **counter-examples** when tests fail
* Generate **executable** versions of counter-examples to load in a debugger
* Generate **complete** models of programs to comprehensively rule out failure cases

Crux is available open-source under the 3-Clause BSD License [on GitHub](https://github.com/GaloisInc/crucible).


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