In this work, a pre-synchronization strategy for Grid-Forming inverters is proposed. This strategy is inspired by the phenomena of spontaneous synchronization of networked oscillators. Contrary to previous works, this solution does not rely upon power set-points, so that implementation for operation in non-rated grid conditions is straightforward, without a control structure to adjust these set-points. The proposed strategy is applied to Dispatchable Virtual Oscillator and Syn-chronverter Grid-forming inverters in a Controller Hardware-In-the-Loop (CHIL) testbed. The results obtained shows that pre-synchronization is achieved in both rated and non-rated grid conditions. The results also shows that the Grid-Forming inverters are able to seamlessly transition to grid-connected operation for the studied Grid-forming strategies.