I wrote a set of test cases, see mini2_test.erl. I've tried these with both of my solutions to the mini assignment, and they both pass all of the tests. While this isn't surprising -- I wrote both the solutions and the tests -- it gives me some hope that these tests should work well with other solutions as well, including yours.
I found that it's handy to be able to run the tests with any output from the the code actually being printed. In particular, this let me put io:format statements in my code to trace the interaction between the different processes. Yeah, it's debugging with printf statements, but it got the job done. The standard EUnit interface suppresses output from the code under test. So, I wrote function try_it/0, try_it/1, and try_it/2 at the end of mini2_test.erl that let you run sets of tests on particular refrigerators with the output displayed. I found I could debug pretty quickly once I had that.