Harry decides to test them on himself first

Abruptly, Harry stood. These powers were too dangerous to test on anyone else, he had to do things to himself first. Understand exactly how they worked, before he did anything. Hermione was staring at him in complete confusion, but Harry didn't care. He couldn't say anything to anyone, just in case he used the wrong phrase and did something horrible to them.

He practically ran out of the common room, ignoring Hermione as she began to protest.

He kept his mouth shut as he made his way to the Room of Requirement. It was the only place in Hogwarts he knew he wouldn't be disturbed.

Pacing in the seventh-floor corridor, Harry thought to himself:

'I want a room where no one will find me.'

He repeated that thought over and over until the door to the Room materialised in front of him. Quickly pushing his way through, Harry found himself in a room that was mostly bare.

If anything, it looked like a bedroom. There was a bed on one side, a grand things with posts and silk sheets, and a small fireplace opposite, with a cosy-looking rug around it. The only other adornment in the room was a full-body mirror, in between the bed and the fireplace.

With a sigh, Harry let himself relax. He would be able to test his power in here without any interruptions.