Check out this behind-the-scenes look at Apple's development process: Flickr member jimabeles posted a great gallery of photographs of a 13-inch MacBook test unit. He labeled it a prototype, but some folks on reddit identified it as the more proper name of EVT, or engineering validation test unit. EVT units are apparently used to test the hardware components in a way that offers engineers direct access to those components. What you and I might think of as a "prototype" is designated a DVT, or design validation test unit. You can see the EVT label on many of the pictures in the full gallery. Normally we'd say look quickly before Apple has the gallery pulled down, but most of these photographs have been on Flickr since 2010. This member has a number of other galleries of similar Apple development products.