We'll start by reviewing a harness which is a typical example..
Harnesses are generally subjected to a 15kN tensile force. These forces are applied and held for at least 3 minutes, to ensure the breaking strength of the product is in excess of the force specified by the standard. This is in addition to dynamic test forces.
Although a harness will be subjected to relatively high test forces, the normal safe working load of a harness will range between 100kg-140kg dependent on the manufacturer to ensure there is an adequate factor of safety.