Dicetest

Dicetest is a framework for writing tests with pseudorandom generated test data.

Status of this crate

The author does not consider this crate as stable yet.

Simple example

Here's an example of a broken sort function tested with Dicetest:

fn bubble_sort<T: Ord>(slice: &mut [T]) {
    let len = slice.len();

    for _ in 0..len {
        for j in 1..len - 1 {
            let jpp = j + 1;
            if slice[j] > slice[jpp] {
                slice.swap(j, jpp);
            }
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use dicetest::prelude::tests::*;

    #[test]
    fn result_of_bubble_sort_is_sorted() {
        dicetest!(|fate| {
            let mut v = dice::vec(dice::u8(..), ..).roll(fate);
            hint!("unsorted: {:?}", v);

            bubble_sort(&mut v);
            hint!("  sorted: {:?}", v);

            let is_sorted = v.windows(2).all(|w| w[0] <= w[1]);
            assert!(is_sorted);
        })
    }
}

Running cargo test produces the following output:

The test failed after 36 passes.

# Config
- seed: 795359663177100823
- start limit: 0
- end limit: 100
- passes: 1000

# Counterexample
- run code: "ABIDje/+CYVkmmCVTwKJ2go6VrzZWMjO2Bqc9m3b3h0DAAAAAAAAAA=="
- limit: 3
- hints:
    - unsorted: [255, 252, 131]
    -   sorted: [255, 131, 252]
- error: assertion failed: is_sorted

You can rerun the counterexample by setting a environment variable:

DICETEST_DEBUG=ABIDje/+CYVkmmCVTwKJ2go6VrzZWMjO2Bqc9m3b3h0DAAAAAAAAAA== cargo test

Alternatives

Write down your test data and use a loop.
Use the crate quickcheck.
Use the crate proptest.

License

Licensed under either of

Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contribution