St. Jane de Chantal, as Foundress of the Visitation Order, could not be too careful in whom she accepted into the novitiate.
She said in her Answers, page 306, “The happiness and preservation of our Congregation depend on the good choice of subjects, and on the care we shall take to ground them well in true virtues. In the name of God, let us keep firm on this matter; and never let human consideration enter into their reception, but inspiration alone. I would write this with my blood, so great do I know its importance to be.”
The key is true virtue; a discerner must ultimately be seeking to grow in virtue, goodness, holiness, and support for this will be given by the formation directress and community.
Pray to St Jane as her Feast approaches on August 12th. She will help you make a good discernment.