Function change_case::swap_case

pub fn swap_case(input: &str) -> String

Change to swap case

use change_case::swap_case;
assert_eq!(swap_case(""), "");
assert_eq!(swap_case("test"), "TEST");
assert_eq!(swap_case("test string"), "TEST STRING");
assert_eq!(swap_case("Test String"), "tEST sTRING");
assert_eq!(swap_case("TestV2"), "tESTv2");
assert_eq!(swap_case("sWaP cAsE"), "SwAp CaSe");