When installation tests are run on a user system using the OS X installer, the three tests fail with a crash.  Similar results would be expected on other unix-y platforms when tests are run from the install destination, and not the source or build directories (which do not exist on user systems using installers). On 3.1.2rc1 and py3k, each crashes on an import error:

  test test_{tk,ttk_guionly,ttk_textonly} crashed -- <class 'ImportError'>: No module named test

On trunk (2.7), they crash with;
  test test_{tk,ttk_guionly,ttk_textonly} crashed -- <type 'exceptions.ImportError'>: No module named runtktests

The problem is that the test subdirectories are not being installed by the libinstall Makefile target.  For 3.1.2rc1 and py3k, adding the directories to LIBSUBDIRS should get them installed:
  LIBSUBDIRS= tkinter site-packages test test/output test/data \
    tkinter/test tkinter/test/test_tkinter tkinter/test/test_ttk \
    test/decimaltestdata \ {...}
(Trunk is slightly different.)

Fixed in r79056.