There are two basic types, ones with a separate freezer compartment and ones with the freezer inside the refrigerator section. Testers put thermocouples throughout the refrigerator section to measure the temperature. In the freezer section, thermocouples are put into packages of frozen spinach. Testers monitor how evenly each refrigerator maintains the temperature in both sections.
Almost every mini-fridge had inconsistent temperatures. In two-door models, the problem was worse in the refrigerator section, and in the other models, it was in the freezer.
Testers used an audio sensor to measure the noise level of each fridge. Some are much louder than others. Energy efficiency is another area where testers found big differences. Some of the compact refrigerators cost almost as much to run as a full- sized model, even though they have only about a quarter of the space.
In the end, Consumer Reports found that most of the mini-refrigerators tested didn't perform well. But testers did find one to recommend. The Frigidaire FFPH44M4L costs $220, and both the fridge and freezer sections keep their cool.
Consumer Reports says before you buy a mini-fridge for a dorm room, check the rules at your school. Some colleges don't allow fridges, and others require that you rent them from the school itself.