Got our first test passing.  When Mia tries to buy something with zero dollars, she can't buy anything.
Mia cannot buy anything when she has 50 cents.
Mia can buy a pinwheel with 87 cents.
When we ask what we can buy from a store, we get multiple shopping baskets back because there are multiple options for what you can buy.  We don't have all of the tests passing yet, but it's bedtime.