Macro assertables::assert_fn_eq_as_result

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

Assert a function output is equal to a given.

• If true, return Result Ok(()).

• Otherwise, return Result Err with a diagnostic message.

Examples

let a: i32 = -1;
let b: i32 = 1;
let x = assert_fn_eq_as_result!(i32::abs, a, b);
//-> Ok(())
assert!(x.is_ok());

let a: i32 = -1;
let b: i32 = 2;
let x = assert_fn_eq_as_result!(i32::abs, a, b);
//-> Err(…)
let actual = x.unwrap_err();
let expect = concat!(
    "assertion failed: `assert_fn_eq!(left_function, left_input, right_expr)`\n",
    " left_function label: `i32::abs`,\n",
    "    left_input label: `a`,\n",
    "    left_input debug: `-1`,\n",
    "    right_expr label: `b`,\n",
    "    right_expr debug: `2`,\n",
    "                left: `1`,\n",
    "               right: `2`"
);
assert_eq!(actual, expect);