A continuity tester should be utilized to located and isolate shorts in wiring and never used to to test cables or any distribution equipment for possible shorts.
A megger can be used for predictive maintenance if utilized when equipment is new to establish a base line, then periodically for tracking equipment insulation values at a point based upon company standards or published standards the equipment can be slated for replacement prior to failure (in theory).
A megger will show a short from carbon in a fault distribution equipment a continuity tester won't unless the equipment is so trashed it is visibly obvious.
In the picture below a continuity tester would show no fault the megger shows issues.
Standard school paper, pencil lead (carbon), 1000 VDC test voltage