The tests might not work with OSX because of some funky matploblib behavior. When the testing script tries to import matplotlib you might get an error: " RuntimeError: Python is not installed as a framework...See 'Working with Matplotlib on OSX' in the Matplotlib FAQ for more information". See this stackoverflow post .
The solution is to make a file called matplotlibrc in the directory ~/.matplotlib then add the line backend: TkAgg. In particular:
cd User/YOURNAME/.matplotlib
vi matplotlibrc
then add the line: backend: TkAgg