In general it's not possible to have those tests pass with arbitrary settings. To remedy this, the new test runner in Django 1.6 [1] won't pick up Django's tests that are part of contrib apps.
On a related note, consider upgrading to a supported version of Django (1.7+), or at least the last release in the 1.5 series (1.5.12) which remedies several security issues in 1.5.4.
[1]
https://docs.djangoproject.com/en/stable/releases/1.6/#discovery-of-tests-in-any-test-module