Wandtesting is when young Gardnerians are tested to see what their Mage skill level is.
When a Gardnerian child is wandtested, they hold a wand and speak a specific spell. Their Mage skill level will be revealed and is determined to be a Level 1 through Level 5, with Level 1 being the weakest and Level 5 being the strongest.
Elloren is wandtested by Uncle Edwin when she was three years old. She is placed at a Level 1, meaning she has no power.
Later, it is revealed that Uncle Edwin altered her results to protect her. He convinced her that the forest fire she started when conducting the test was only a dream.