The Light Ranger Mobile Universal Trailer Tester (MUTT) is a portable and water resistant trailer light tester and trailer brakes tester that allows the user to perform all testing functions without the use of the vehicle. For 7-spade, 6-round and 4/5 flat pin trailer harnesses, the Light Ranger MUTT simulates all electrical circuits of standard towing vehicles for boating, RV, landscaping, hunting and similar type light duty trailers. Included with each tester is a battery charger and 3-way trailer harness adapter.