Most RecyclerViewActions are given a matcher to select a particular view / viewholder within
the RecyclerView. In this case the default behaviour is to expect that the matcher matches 1
and only one item within the RecyclerView.
This interface gives users the ability to override that type of behaviour and explicitly
select an item in the RecyclerView at a given position. This is similar to on the
onData(...).atPosition() api for AdapterViews.
RecyclerViewActions.PositionableRecyclerViewAction atPosition (int position)
Returns a new ViewAction which will cause the ViewAction to operate upon the position-th
element which the matcher has selected.
a 0-based index into the list of matching elements within the RecyclerView.
|if position < 0.