Assert a function err() is less than another.
fn f(i: i8) -> Result<String, String> { match i { 0..=9 => Ok(format!("{}", i)), _ => Err(format!("{:?} is out of range", i)), } } let a: i8 = 10; let b: i8 = 20; assert_fn_err_lt!(f, a, f, b);
assert_fn_err_lt
assert_fn_err_lt_as_result
debug_assert_fn_err_lt