The easiest way to test how cooked your steak is, is to press on the meat with your fingertips.
Press on the meat here and there while it cooks, and compare the feeling of the meat with the following finger test. You’ll get better with practice.
Open the palm of your hand. Relax the hand. With your other index finger push on the fleshy area between the thumb and the base of the palm. This is what raw meat feels like.
Press the tip of your index finger to the tip of your thumb. The fleshy area below the thumb should give quite a bit. This is what rare meat feels like. This is what rare meat feels like.
Gently press the tip of your middle finger to the tip of your thumb. Feel the flesh beneath the thumb. This is what medium rare meat feels like.
Press the tip of your ring finger and your thumb together. The flesh beneath the thumb should give a little more. This is what medium cooked meat feels like.