assert-not-modified

Rust wrapper function which checks that the given closure does not modify input data.

This is helpful when checking that a function which returns Err(...) does not have side-effects.

Example

```rust use assertnotmodified::assertnotmodified;

// This bugged function wil return Err but still modify the data. fn misleadingerr(x: &mut i32) -> Result<(), String> { *x = *x + 1; // Throws an error but x is modified anyway. This is misleading. Err("Something wrong happened !".toowned()) }

// This test will expose the lying function : assert!(std::panic::catchunwind(|| { let mut x = 3; assertnotmodified(&mut x, |x| misleadingerr(x)); // Panics }) .is_err()); ```