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