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:

```rust,ignore

[macrouse] extern crate prettyassertions;

```

Show the example behind the screenshots above.

``rust,ignore // 1. add thepretty_assertionsdependency toCargo.toml`. // 2. insert this line at the top of your crate root or integration test

[macrouse] extern crate prettyassertions;

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

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:

```rust,ignore

[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.
assert_ne is also switched to multi-line presentation, but does not show a diff.

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.