This article describes the specifics of WEC physical testing compared to offshore platform testing and exposes the reasons of performing initial tests at small scales. The first difference is that WECs have larger and thus more nonlinear motions. These large amplitudes of motions imply the necessity of a rigorous representation of the rotation of the device. The second difference is the definite influence on the PTO on the WEC motions. The PTO has therefore to be physically modeled. The third difference is in the mooring philosophy: in case of floating WECs, the mooring is to be designed to give the maximal freedom of motion to the devices, which is not usually the case for offshore platforms. WEC design is today not an established technique; the uncertain points still have to be assessed with a sufficient level of confidence. This implies their physical testing at the preliminary study stage at small scales and subsequently their physical testing at larger scales. The testing of the OE Buoy WEC at these larger scales validated the results obtained at small scales.