115 lines
4.1 KiB
Markdown
115 lines
4.1 KiB
Markdown
# Pretty Assertions
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[](https://crates.io/crates/pretty-assertions)
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[](https://docs.rs/pretty_assertions)
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[](https://crates.io/crates/pretty-assertions)
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[](https://crates.io/crates/pretty-assertions)
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Overwrite `assert_eq!` with a drop-in replacement, adding a colorful diff.
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## Usage
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When writing tests in Rust, you'll probably use `assert_eq!(a, b)` _a lot_.
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If such a test fails, it will present all the details of `a` and `b`.
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But you have to spot the differences yourself, which is not always straightforward,
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like here:
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Wouldn't that task be _much_ easier with a colorful diff?
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Yep — and you only need **one line of code** to make it happen:
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```rust,ignore
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use pretty_assertions::{assert_eq, assert_ne};
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```
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<details>
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<summary>Show the example behind the screenshots above.</summary>
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```rust,ignore
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// 1. add the `pretty_assertions` dependency to `Cargo.toml`.
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// 2. insert this line at the top of each module, as needed
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use pretty_assertions::{assert_eq, assert_ne};
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fn main() {
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#[derive(Debug, PartialEq)]
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struct Foo {
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lorem: &'static str,
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ipsum: u32,
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dolor: Result<String, String>,
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}
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let x = Some(Foo { lorem: "Hello World!", ipsum: 42, dolor: Ok("hey".to_string())});
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let y = Some(Foo { lorem: "Hello Wrold!", ipsum: 42, dolor: Ok("hey ho!".to_string())});
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assert_eq!(x, y);
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}
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```
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</details>
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## Semantic Versioning
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The exact output of assertions is **not guaranteed** to be consistent over time, and may change between minor versions.
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The output of this crate is designed to be read by a human. It is not suitable for exact comparison, for example in snapshot testing.
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This crate adheres to semantic versioning for publically exported crate items, **except** the `private` module, which may change between any version.
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## Tip
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Specify it as [`[dev-dependencies]`](http://doc.crates.io/specifying-dependencies.html#development-dependencies)
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and it will only be used for compiling tests, examples, and benchmarks.
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This way the compile time of `cargo build` won't be affected!
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Also add `#[cfg(test)]` to your `use` statements, like this:
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```rust,ignore
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#[cfg(test)]
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use pretty_assertions::{assert_eq, assert_ne};
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```
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## Notes
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- Since `Rust 2018` edition, you need to declare
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`use pretty_assertions::{assert_eq, assert_ne};` per module.
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Before you would write `#[macro_use] extern crate pretty_assertions;`.
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- The replacement is only effective in your own crate, not in other libraries
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you include.
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- `assert_ne` is also switched to multi-line presentation, but does _not_ show
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a diff.
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- Under Windows, the terminal state is modified to properly handle VT100
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escape sequences, which may break display for certain use cases.
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- The minimum supported rust version (MSRV) is 1.35.0
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### `no_std` support
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For `no_std` support, disable the `std` feature and enable the `alloc` feature:
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```toml
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# Cargo.toml
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pretty_assertions = { version= "...", default-features = false, features = ["alloc"] }
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```
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## License
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Licensed under either of
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- Apache License, Version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or <http://www.apache.org/licenses/LICENSE-2.0>)
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- MIT license ([LICENSE-MIT](LICENSE-MIT) or <http://opensource.org/licenses/MIT>)
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at your option.
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### Contribution
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Unless you explicitly state otherwise, any contribution intentionally
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submitted for inclusion in the work by you, as defined in the Apache-2.0
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license, shall be dual licensed as above, without any additional terms or
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conditions.
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## Development
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- Cut a new release by creating a GitHub release with tag. Crate will be built and uploaded to crates.io by GHA.
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