The reliability of marine renewable energy (MRE) converters is a key issue that has to be addressed and included in a whole system approach, in order to make the energy extraction from these sources a viable option. At the current development stage of MRE converters, an increasing number of devices are being field tested at pre-commercial demonstration scale, yielding field experience and load data useful for refining, demonstrating and improving the reliability of devices. This paper gives a brief review of the most advanced technologies and common reliability aspects that provide the rationale for dedicated component testing. It describes a service simulation test approach and the development of a unique large-scale component test facility. The test rig is capable of replicating the forces and motions experienced by components for a range of floating marine applications. The replication of motion angles is demonstrated in this paper. The service simulation test of a marine power cable is presented as a case study on how component performance can be assessed and demonstrated prior to long-term field deployments in order to ensure the reliability of crucial sub-systems and components in the harsh marine environment.