When using => expected syntax it could be nice to set up what assertion shall we use.
It might be extra attribute:
#[test_case("foo" => "bar")]
#[test_case_assert_macro(assert_diff)]
fn test(input: &str) -> String { input.to_string() }
this could be expanded into:
mod test {
use super::*;
fn test(input: &str) -> String { input.to_string() }
#[test]
fn foo_expects_bar() {
let actual = test("foo");
assert_diff!("bar", actual);
}