Macro __result_of_ref 

macro_rules! __result_of_ref {
    ($function: expr, $matcher: expr) => { ... };
}

Matches a value where the reference to the result of callable applied to the value matches the inner matcher.

The callable will be called twice, so make sure it is pure.

use googletest::prelude::*;
fn should_pass_1() -> googletest::Result<()> {
   verify_that!("hello", result_of_ref!(|s: &str| s.to_uppercase(), eq("HELLO")))?; // Passes
   Ok(())
}

fn should_pass_2() -> googletest::Result<()> {
   verify_that!(100, result_of_ref!(|value| value + 1, eq(&101)))?; // Passes
   Ok(())
}

fn should_fail() -> googletest::Result<()> {
   verify_that!("world", result_of_ref!(|s: &str| s.to_uppercase(), eq("HELLO")))?; // Passes
   Ok(())
}
should_pass_1().unwrap();
should_pass_2().unwrap();
should_fail().unwrap_err();