Macro assertables::assert_fn_err_lt_other_as_result

macro_rules! assert_fn_err_lt_other_as_result {
    ($function:path, $a_input:expr, $b_input:expr $(,)?) => { ... };
}

Assert one function ok() is less than another.

• If true, return Result Ok(()).

• Otherwise, return Result Err with a diagnostic message.

Examples

fn example_digit_to_string(i: i32) -> Result<String, String> {
    match i {
        0..=9 => Ok(format!("{}", i)),
        _ => Err(format!("{:?} is out of range", i)),
    }
}

let a: i32 = 10;
let b: i32 = 20;
let x = assert_fn_err_lt_other_as_result!(example_digit_to_string, a, b);
//-> Ok(())
let actual = x.unwrap();
let expect = ();
assert_eq!(actual, expect);

let a: i32 = 20;
let b: i32 = 10;
let x = assert_fn_err_lt_other_as_result!(example_digit_to_string, a, b);
//-> Err(…)
let actual = x.unwrap_err();
let expect = concat!(
    "assertion failed: `assert_fn_err_lt_other!(pair_function, left_input, right_input)`\n",
    " pair_function label: `example_digit_to_string`,\n",
    "    left_input label: `a`,\n",
    "    left_input debug: `20`,\n",
    "   right_input label: `b`,\n",
    "   right_input debug: `10`,\n",
    "                left: `\"20 is out of range\"`,\n",
    "               right: `\"10 is out of range\"`"
);
assert_eq!(actual, expect);