While doing a review of the Tracker module from a documentation perspective, it appears that class member variables access_user and no_access_user are not used. These at minimum should be removed and a thorough coding review of the two tests performed.
FAILED: [[SimpleTest]]: [PHP 5.4 MySQL] 81,090 pass(es), 2 fail(s), and 0 exception(s). View
FAILED: [[SimpleTest]]: [MySQL] 47,584 pass(es), 1 fail(s), and 0 exception(s). View