message: Add unit tests for new functionality.
diff: @@ -10,7 +10,7 @@ use crate::{
  };
  /// Information about the context in which a new block is created.
  -#[derive(Clone, DataSize, Eq, PartialEq, Debug, Ord, PartialOrd, Hash)]
  +#[derive(Clone, Copy, DataSize, Eq, PartialEq, Debug, Ord, PartialOrd, Hash)]
  pub struct BlockContext {
  timestamp: Timestamp,
  height: u64,
  