First test, expect bike not to be broken by default
second test case for Bike class, bike should be able to be broken
Third test case for Bike class, bike can now be fixed
DockingStation class first test case, create an empty docking station
DockingStaiotn second test case, docking station should be able to accept bikes
DockingStaiotn third test case, docking station should be able to release bikes
DockingStaiotn fourth test case, docking station should be able to know when it is full
DockingStaiotn fifth test case, docking station should raise an error when trying to dock more bikes after it is full
DockingStaiotn sixth test case, docking station should give a list of working bikes