What is final test to prove her identity?

In the story, "The Lady or the Tiger?", the Princess gives the knight one of two identical doors to open, promising that behind one of them is the true princess, and behind the other is a ferocious tiger. The correct choice will free the knight and allow him to marry the princess, while the wrong choice will result in his death. There is no final test to prove her identity, as the reader is left to speculate on which door hides the true princess and which conceals the tiger. The knight must make his decision based on his own intuition and judgment, with no certainty of the outcome.