Assume a product requires a MAINS to 12Vdc power supply < 50W
A suitable power supply is specified and it meets all required surge testing requirements, it is located within the product.
Now if the power supply is moved outside of the device, from what I recall once the distance of the interconnecting dc power cables exceeds a certain length (1M possibly), then I think surge testing is required on the DC input terminals in addition to the MAINS, can anyone confirm this?