Fix and implement tests for used to named unique now distincByDocId function

[lenguyenthanh]

No description provided.

[lenguyenthanh]

Hi @gravetii, I refactored and added tests for unique function and just realized the old implementation was subtly (but seriously) wrong.

Let's look at this:

  def unique: List[ChangeStreamDocument[A]] =
    changes
      .foldRight(List.empty[ChangeStreamDocument[A]] -> Set.empty) { case (change, p @ (acc, ids)) =>
        if change.docId.exists(!ids.contains(_))
        then (change :: acc) -> (ids + id)
        else p
      }
      ._1

inside unique, id at line 6 just appeared without any reference. It was still compiled because We have an id function in the same file (which is my bad).

p/s: I mentioned this for the shake of the correctness and not for blaming you. Thanks to your effort, I finally sit down and write tests which I should've done for a long time.

[gravetii]

Indeed @lenguyenthanh, you're too kind. apologies for the chaos, the change looks good to me!

[lenguyenthanh]

Indeed @lenguyenthanh, you're too kind. apologies for the chaos, the change looks good to me!

thanks, and please keep contributing, we're really appreciated your contribution!