rustc/tests/ui/macros/assert-eq-macro-msg.rs

// run-fail
// error-pattern:assertion `left == right` failed: 1 + 1 definitely should be 3
// error-pattern:  left: 2
// error-pattern: right: 3
// ignore-emscripten no processes

fn main() {
    assert_eq!(1 + 1, 3, "1 + 1 definitely should be 3");
}