proptest-quickcheck-interop

proptest is a property testing framework (i.e., the QuickCheck family) inspired by the Hypothesis framework for Python.

quickcheck is another property testing framework for Rust which uses a shrinking logic similar to Haskell's QuickCheck.

This crate provides interoperability between quickcheck and proptest. Currently, this is one way - if you've implemented quickcheck's Arbitrary trait as well as Debug, which is a temporary requirement, then you may get back the equivalent Strategy in proptest.

Status of this crate

This crate is unlikely to see major changes. Any breaking changes are only likely to come as a result of changes in the dependencies used by this crate, in particular proptest or quickcheck. When any of those crates make breaking changes that affect this crate, then the major version of this crate will be bumped.

See the changelog for a full list of substantial historical changes, breaking and otherwise.

Using the interoperability layer

Assuming that you already have a Cargo.toml file in your project with, among other things, the following:

[dependencies]

quickcheck = "0.6.0"
proptest   = "0.4.1"

Now add this crate to your dependencies:

[dependencies]

quickcheck = "0.6.0"
proptest   = "0.4.1"
proptest_quickcheck_interop = "2.0.0"

Let's now assume that usize is a complex type for which you have implemented quickcheck::Arbitrary. You wish you reuse this in proptest or if you simply prefer the implementation provided by quickcheck. To do so, you can use from_qc:

// Import crates:
#[macro_use] extern crate proptest;
extern crate proptest_quickcheck_interop as pqci;

// And what we need into our scope:
use proptest::strategy::Strategy;
use pqci::from_qc;

/// Given a usize returns the nearest usize that is also even.
fn make_even(x: usize) -> usize {
    if x % 2 == 1 { x - 1 } else { x }
}

proptest! {
   /// A property asserting that make_even always produces an even usize.
   fn always_even(ref x in from_qc::<usize>().prop_map(make_even)) {
       prop_assert!(x % 2 == 0);
   }
}

fn main() {
    always_even();
}

If you want to control the size of the input generated by quickcheck you may instead use from_qc_sized(size). If you use, from_qc, then the default size used by quickcheck is used.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.