In Treta yuga, when Lord Vishnu took avatar as Raam, Lord Shiva was aware about this and he took avatar as Lord Hanuman.
In the Ramayana there is a part mentioned that when Raam was in forest ( for 14 years vanvas ) with Sita & Laxmana, Godess Parvati went to forest to check actually Raam is Vishnu's avatar or not ? When Raam show her, he simply said why you are alone, where is Lord Shiva ? Hearing this she got confirmed that Raam is an avatar of Lord Vishnu.
Now when she come back to Kailash, Lord Shiva asked her about examination of Raam.
Generally when Vishnu takes any avatar, it is well known among all the devi-devtas.
So in this case Why Godess Parvati was not aware that Raam is actually an avatar of Lord Vishnu while Lord Shiva was very well known about this part ?