Anjana Is Put To Test

As Anjana and Kesari approach Rishi Mathang with their prayer for a baby, he advices them to reach the spot where Vishnu had left his third avatar of Varaha. Anjana and Kesari reach the spot and sincerely pray before the Varaha avatar. Vishnu appears before them in his Varaha avatar and he asks Anjana to do a severe penance in order to impress Lord Shiva. Anjana starts to do the penance and as years pass the warmth of her prayer starts troubling the Gods in the heaven. Goddess Parvathi prays with Shiva to answer Anjana's prayer but Shiva informs her that he has another test for Anjana in his mind. What is this divine test planned by Shiva?