snaptest

Dead simple snapshot testing (inspired by jest).

Documentation (including this README) is a work in progress. Feel free to submit an issue if you have a question about usage.

Features

• Any type that implements Debug can be returned from a test.
• First class integration with failure.
• The snapshot store is thread safe so your tests can run in parallel.
• Beautiful diffs are printed when a snapshot test fails.
• A single small binary file is used to store snapshots.

TODO

Installation

First, add snaptest to the dependencies section of your Cargo.toml:

[dependencies]
snaptest = "0.1"

Next, add the following snippet to the entry point of your crate (lib.rs or main.rs):

#[macro_use]
extern crate snaptest;

Usage

Derive Debug on types that you want to use with snaptest:

#[macro_use]
extern crate failure;
#[cfg_attr(test, macro_use)]
extern crate snaptest;

use std::str::FromStr;

#[derive(Debug)]
enum Hero {
    Batman,
    TheFlash,
    WonderWoman,
}

impl FromStr for Hero {
    type Err = Error;

    fn from_str(value: &str) -> Result<Hero, Self::Err> {
        match value {
            "Batman" => Ok(Hero::Batman),
            "The Flash" => Ok(Hero::TheFlash),
            "Wonder Woman" => Ok(Hero::WonderWoman),
            _ => bail!(r#""{}" is not a hero"#),
        }
    }
}

#[cfg(test)]
mod tests {
    use failure::Error;

    use super::Hero; // no pun intended...

    snaptest!{
        fn parse_heros() -> Result<Vec<Hero>, Error> {
            let heros = ["Batman", "The Flash", "Wonder Woman"];
            heros.iter().map(|hero| hero.parse()).collect()
        }
    }
}

Next time your test runs, a snapshot will be added to a local .snapfile to compare against future test results. If you get a different result back than what matches the snapshot, the test will fail and the diff will be printed to the console.

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.