Crate pretty_assertions [−] [src]
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:
#[macro_use] extern crate pretty_assertions;
Show the example behind the screenshots above.
// 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 thedifference
crate, which does the heavy lifting. All thatpretty_assertions
does is to replace theassert_eq!
macro with just about 22 lines of code.
Macros
assert_eq |