Do you have any reason to think your scale isn't accurate? I would think the best way to test it is with a known weight, like a kettle bell, or weight lifting weights. Maybe even an unopened bag of sugar, pet food or whatever. They are probably fairly accurate with weight.
If you have a small dog or cat that you got his/her weight at the vet recently, that could work. If you see your doctor, weigh yourself at home before you leave, and then see what you weigh there. Or at the gym, if you go to the gym. They calibrate their scales regularly, I assume. If it's close, then you're fine.
If you'd really like a new scale, then the sooner the better. It sucks to get a new scale and find your scale was off several pounds in the wrong direction!
Mine is Taylor brand, glass digital and the one thing I like about this particular model is it turns on when you stand on it. I have another one where I have to tap it with my foot to turn it on before I can stand on it. The only thing I don't like about this scale is that it measures in 0.2 pounds. I wish it measured in 0.1 increments. As if it would make any difference!