pretty_assertions 0.1.1

Overwrite `assert_eq!` with a drop-in replacement, adding a colorful diff.
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Pretty Assertions

When writing tests in Rust, you'll probably use assert_eq!(a, b) a lot.

If such a test fails, it will present all the details of a and b, but you have to spot, the differences yourself, which is not always straightforward, like here:

standard assertion

Wouldn't that task be much easier with a colorful diff?

pretty assertion

Yep — and you only need one line of code to make it happen:

#[macro_use] extern crate pretty_assertions;
// 1. add the `pretty_assertions` dependency to `Cargo.toml`.
// 2. insert this line at the top of your crate root or integration test
#[macro_use] extern crate pretty_assertions;

fn main() {
    #[derive(Debug, PartialEq)]
    struct Foo {
        lorem: &'static str,
        ipsum: u32,
        dolor: Result<String, String>,
    }

    let x = Some(Foo { lorem: "Hello World!", ipsum: 42, dolor: Ok("hey".to_string())});
    let y = Some(Foo { lorem: "Hello Wrold!", ipsum: 42, dolor: Ok("hey ho!".to_string())});

    assert_eq!(x, y);
}

Tip

Specify it as [dev-dependency] and it will only be used for compiling tests, examples, and benchmarks. This way the compile time of cargo build won't be affected!

In your crate root, also add #[cfg(test)] to the crate import, like this:

#[cfg(test)] // <-- not needed in examples + integration tests
#[macro_use]
extern crate pretty_assertions;

Note

  • Each example and integration test also needs #[macro_use] extern crate pretty_assertions, if you want colorful diffs there.
  • The replacement is only effective in your own crate, not in other libraries you include.
  • pretty_assertions is an ultra-thin wrapper around the difference crate, which does the heavy lifting. All that pretty_assertions does is to replace the assert_eq! macro with just about 22 lines of code.

License

Licensed under either of

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.