fn main() { let x = 1; let y = 2; debug_assert!(x <= y, "{} > {}", x, y); debug_assert_eq!(x, y); assert!(x <= y, "{} != {}", x, y); assert_eq!(x, y); } $ cd test_example1 $ cargo run thread '<main>' panicked at 'assertion failed: `(left == right)` (left: `1`, right: `2`)', src\main.rs:6 An unknown error occurred