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:
Wouldn't that task be much easier with a colorful diff?
Yep — and you only need one line of code to make it happen:
use pretty_assertions::{assert_eq, assert_ne};
// 1. add the `pretty_assertions` dependency to `Cargo.toml`.
// 2. insert this line at the top of each module, as needed
use pretty_assertions::{assert_eq, assert_ne};
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-dependencies]
and it will only be used for compiling tests, examples, and benchmarks.
This way the compile time of cargo build won't be affected!
Also add #[cfg(test)] to your use statements, like this:
#[cfg(test)]
use pretty_assertions::{assert_eq, assert_ne};
Note
- Since
Rust 2018edition, you need to declare
use pretty_assertions::{assert_eq, assert_ne};per module.
Before you would write#[macro_use] extern crate pretty_assertions;. - The replacement is only effective in your own crate, not in other libraries
you include. assert_neis also switched to multi-line presentation, but does not show
a diff.- Under Windows, the terminal state is modified to properly handle VT100
escape sequences, which may break display for certain use cases.
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.