message: Verify that synchronizer manages syncing state properly.
diff: @@ -152,7 +152,7 @@ fn do_not_download_synchronized_dependencies() {
  TEST_INSTANCE_ID,
  );
  - let highway = Highway::<TestContext>::new(TEST_INSTANCE_ID, test_validators(), params);
  + let mut highway = Highway::<TestContext>::new(TEST_INSTANCE_ID, test_validators(), params);
  let now = 0x20.into();
  assert!(matches!(
  @@ -186,6 +186,26 @@ fn do_not_download_synchronized_dependencies() {
  &peer0,
  HighwayMessage::RequestDependency(Dependency::Unit(c0)),
  );
  + // "Download" the last dependency.
  + let _ = sync.schedule_add_vertex(peer0, pvv(c0), now);
  + // Now, the whole chain can be added to the protocol state.
  + for unit in &[c0, c1, b0, c2] {
  + let (maybe_pv, outcomes) = sync.pop_vertex_to_add(&highway);
  + assert_eq!(Dependency::Unit(*unit), maybe_pv.unwrap().vertex().id());
  + // Verify that we don't request any dependency now.
  + assert!(
  + !outcomes
  + .iter()
  + .any(|outcome| matches!(outcome, ProtocolOutcome::CreatedTargetedMessage(_, _))),
  + "unexpected dependency request {:?}", outcomes
  + );
  + let vv = highway
  + .validate_vertex(pvv(*unit))
  + .unwrap_or_else(|_| panic!("{:?} unit is valid", unit));
  + highway.add_valid_vertex(vv, now);
  + let _ = sync.remove_satisfied_deps(&highway);
  + }
  + assert!(sync.is_empty());
  }
  #[cfg(test)]
  