'The property should return None if an upgrade cannot be upgraded.'

@skip_unless_lms
@ddt.data(*(set(CourseMode.ALL_MODES) - set(CourseMode.AUDIT_MODES)))
def test_upgrade_deadline_for_non_upgradeable_enrollment(self, mode):

    enrollment = CourseEnrollmentFactory(course_id=self.course.id, mode=mode)
    self.assertIsNone(enrollment.upgrade_deadline)
