Q: The tests send the message setSize: to the heap.
A: Oops, forgot to mention that. It's the total number of words in the heap.
NB: I unintentionally confused some people. The BitArray class we developed in class is only to be used for the marks (each word has a mark bit). The heap itself should be an array, created with Array new: n where n is how big the heap should be. The ManagedHeap class should have a heap which is a normal array, as well as a marks structure which is initialized as a BitArray.