The rice cookers I tested fell into three loose categories: small, affordable devices, midrange multicookers and specialized, high-end rice cookers.Each mini rice cooker I tested, including the Imusa 3-cup, the Dash mini 2-cup rice cooker, and the Black & Decker 3-cup rice cooker offered decent, small servings of white rice — although the Dash took a painfully long 35 minutes just to cook…