Implement basic test for the client interface

src/lib.rs

@@ -123,6 +123,7 @@ fn derive_protocol(input: proc_macro2::TokenStream) -> proc_macro2::TokenStream
 
     // Create an error and result type for sending messages
     let error_enum = quote! {
+        #[derive(Debug)]
         #vis enum #error_enum_name {
             SendError(tokio::sync::mpsc::error::SendError<(u64, #question_enum_name)>),
             Closed,