message: Add a test for datatype size
diff: @@ -317,6 +317,7 @@ pub mod tests {
  assert_eq!(desc, $desc);
  let dt = Datatype::from_type::<$ty>().unwrap();
  assert_eq!(desc, dt.to_descriptor().unwrap());
  + assert_eq!(dt.size(), desc.size());
  })
  }
  