# assert-panic
[](https://crates.io/crates/assert-panic)
[](https://docs.rs/assert-panic/1.0.0/assert_panic/macro.assert_panic.html)
This library provides a macro that asserts that a panic happens, and optionally what (kind of) panic happens.
The simplest version gives you the panic as boxed `Any`.
## Example
```rust
# use std::any::Any;
use assert_panic::assert_panic;
let _: Box<dyn Any + Send + 'static> =
assert_panic!(panic!("at the Disco"));
assert_panic!(panic!("at the Disco"), &str);
assert_panic!(
{ assert_panic!({}); },
String,
starts with "assert_panic! argument did not panic:",
);
assert_panic!(
assert_panic!(panic!("at the Disco"), String),
String,
starts with "Expected a `String` panic but found one with TypeId { t: ",
);
assert_panic!(
assert_panic!(panic!("found"), &str, contains "expected"),
String,
"Expected a panic containing \"expected\" but found \"found\"",
);
assert_panic!(
assert_panic!(panic!("found"), &str, starts with "expected"),
String,
"Expected a panic starting with \"expected\" but found \"found\"",
);
assert_panic!(
assert_panic!(panic!(1_usize), usize, 2_usize),
String,
"Expected a panic equal to 2 but found 1",
);
```
## Versioning
`assert-panic` strictly follows [Semantic Versioning 2.0.0](https://semver.org/spec/v2.0.0.html) with the following exceptions:
- The minor version will not reset to 0 on major version changes.
Consider it the global feature level.
- The patch version will not reset to 0 on major or minor version changes.
Consider it the global patch level.
- Panic messages originating from `assert-panic` are considered an implementation detail.
Please only evaluate panic values you have direct control over.