A test-drive is when you drive a car for a short time before buying it, to find out how it feels — how it turns, how the seat fits you, whether the engine sounds right. Car sellers expect this and will offer it. As a noun you take a test-drive or go on a test-drive; it is often written with a hyphen, sometimes as two words. It is also a verb: to test-drive a car. And people stretch it well beyond cars. If you try something out for a while before you commit to it, you can say you are test-driving it — a new phone, a piece of software, even, half-jokingly, a new job or a new hairstyle. That stretched use is casual and friendly, and it always keeps the flavour of 'trying before deciding', not just 'using'.