message: Test add_iterator explicitely
diff: @@ -221,8 +221,6 @@ mod test {
  let querier =
  MockQuerier::new(&[(&HumanAddr::from(INIT_ADDR), &coins(INIT_AMOUNT, INIT_DENOM))]);
  move_into_context(instance.context_mut(), storage, querier);
  - #[cfg(feature = "iterator")]
  - let _ = add_iterator::<S, Q>(instance.context_mut(), Box::new(std::iter::empty()));
  }
  #[test]
  @@ -248,6 +246,23 @@ mod test {
  assert!(endq.is_none());
  }
  + #[test]
  + #[cfg(feature = "iterator")]
  + fn add_iterator_works() {
  + let mut instance = make_instance();
  + leave_default_data(&mut instance);
  + let ctx = instance.context_mut();
  +
  + assert_eq!(get_context_data::<S, Q>(ctx).iterators.len(), 0);
  + let id1 = add_iterator::<S, Q>(ctx, Box::new(std::iter::empty()));
  + let id2 = add_iterator::<S, Q>(ctx, Box::new(std::iter::empty()));
  + let id3 = add_iterator::<S, Q>(ctx, Box::new(std::iter::empty()));
  + assert_eq!(get_context_data::<S, Q>(ctx).iterators.len(), 3);
  + assert!(get_context_data::<S, Q>(ctx).iterators.contains_key(&id1));
  + assert!(get_context_data::<S, Q>(ctx).iterators.contains_key(&id2));
  + assert!(get_context_data::<S, Q>(ctx).iterators.contains_key(&id3));
  + }
  +
  #[test]
  fn with_storage_set_get() {
  // this creates an instance
  @@ -356,7 +371,8 @@ mod test {
  leave_default_data(&mut instance);
  let ctx = instance.context_mut();
  - with_iterator_from_context::<S, Q, _, ()>(ctx, 1, |iter| {
  + let id = add_iterator::<S, Q>(ctx, Box::new(std::iter::empty()));
  + with_iterator_from_context::<S, Q, _, ()>(ctx, id, |iter| {
  assert!(iter.next().is_none());
  Ok(())
  })
  