message: Add helper macro to create multiple endorsements.
diff: @@ -100,6 +100,12 @@ macro_rules! add_unit {
  /// Creates an endorsement of `vote` by `creator` and adds it to the state.
  macro_rules! endorse {
  + ($state: ident, $rng: ident, $vote: expr; $($creators: expr),*) => {
  + let creators = vec![$($creators.into()),*];
  + for creator in creators.into_iter() {
  + endorse!($state, $rng, creator, $vote);
  + }
  + };
  ($state: ident, $rng: ident, $creator: expr, $vote: expr) => {
  let endorsement: Endorsement<TestContext> = Endorsement::new($vote, ($creator));
  let signature = TestSecret(($creator).0).sign(&endorsement.hash(), &mut $rng);
  