* Comfortable clothing: Jeans, khakis, or sweatpants are all fine. Avoid anything too tight or that might ride up and bother you while you're sitting.
* Layers: Testing centers can be surprisingly warm or cold. A t-shirt or long-sleeved shirt layered with a sweater or light jacket allows you to adjust to the temperature.
* Comfortable shoes: You'll likely be doing some walking, so wear comfortable shoes. Avoid high heels or anything that might make you uncomfortable.
* Avoid distracting clothing: Skip anything with loud patterns, bright colors, or potentially offensive imagery. You want to focus on the test, not your outfit.
Essentially, dress as you would for a comfortable day at school. Focus on practicality and comfort over fashion.