#[derive(Debug, PartialEq)]
struct MyError {}

fn test_me(return_err: bool) -> Result<u32, MyError> {
    if return_err {
        return Err(MyError{});
    }else {
        return Ok(5);
    }
}

#[cfg(test)]
mod test {
    use super::*;

    macro_rules! test_cases {
        ($($name:ident: $value:expr,)*) => {
            $(
                #[test]
                fn $name() {
                    let (return_err, expected) = $value;

                    let result = test_me(return_err);

                    match expected {
                        Ok(_) => assert!(result.is_ok()), // just make sure it's ok
                        Err(_) => assert_eq!(result.unwrap_err(), expected.unwrap_err()) // actually compare the error
                    }
                }
            )*
        }
    }

    test_cases! {
        test_0: (false, Ok(())), // I expect an Ok, but I don't care about the value
        test_1: (true, Err(MyError{})), // I expect an error
    }
}