Challenging the Test
This trophy is awarded for completing a Test Time mission.
I personally got this trophy on the Star mission on rank 12. I feel that I had completed a timed mission before this, and this was the first one that I attempted following the completion of Donder Quest. It is worth pointing out that only times events in the Mission category (third selection down on the Donder Quest menu) will count to this, and not in the Quest (second selection down) category.
Credit to HighflyerVII