dicetest

Framework for writing tests with randomly generated test data.

Status of this crate

The author does not consider this crate as stable yet. Changes will be documented in the changelog.

Example

Here's an example of an incorrect 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::*;

    #[test]
    fn result_of_bubble_sort_is_sorted() {
        Dicetest::repeatedly().run(|mut fate| {
            let mut v = fate.roll(dice::vec(dice::u8(..), ..));
            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 31 passes.

# Config
- seed: 3713861809241954222
- start limit: 0
- end limit: 100
- passes: 200

# Counterexample
- run code: "/yiA1sab3S4UnCf4ozyMpxMxzg1NtFybCuYLHy0/oscDAAAAAAAAAA=="
- limit: 3
- hints:
    - unsorted: [201, 209, 2]
    -   sorted: [201, 2, 209]
- error: assertion failed: is_sorted

You can rerun the counterexample by setting an environment variable:

DICETEST_DEBUG=/yiA1sab3S4UnCf4ozyMpxMxzg1NtFybCuYLHy0/oscDAAAAAAAAAA== cargo test

Or you can modify the test:

Dicetest::debug("/yiA1sab3S4UnCf4ozyMpxMxzg1NtFybCuYLHy0/oscDAAAAAAAAAA==").run(|mut fate| {
    // ...
})

After fixing the bug you can keep the counterexample as a regression test:

Dicetest::repeatedly()
    .regression("/yiA1sab3S4UnCf4ozyMpxMxzg1NtFybCuYLHy0/oscDAAAAAAAAAA==")
    .run(|mut fate| {
        // ...
    })

For a more comprehensive explanation of dicetest, see the guide.

Features

These features are available:

• Generators for many libstd types (u8, String, Vec, etc.).
• Generators for functions (FnMut, FnOnce, Fn).
• Generator combinators (map, flat_map, zip, etc.).
• Integration of rand::distributions::Distribution.
• Configurable test runner.
• Utilities for debugging tests (hints and stats).

These features are missing:

• Derivable trait for arbitrary types.
• Shrinking of counterexamples.
• Custom pseudorandom number generators.

Alternatives

• Write down your test data and use a loop.
• Use the crate arbitrary and arbtest.
• 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

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.