Currently there is no fusion neutron dedicated source with a high enough flux to mimic irradiation conditions relevant to those to be experienced by the First Wall in a fusion reactor. Nevertheless, very valuable information can be obtained from existing irradiation sources, in particular Materials Test Reactors, Fast neutron reactors and Ion accelerators. Partial information is provided by these irradiation facilities that can be used to down select main materials candidates for DEMO fusion reactors and evaluate their performance under limited conditions. Modelling is an indispensable tool to interpret all the available information and build a test matrix of experiments to be carried out in a dedicated fusion neutron source.Available tools for testing materials exposed to ion or neutron irradiation, including their advantages and limitations when mimicking fusion conditions, are discussed in this paper. Next generation of fusion devices, such as DEMO, will need the input provided by a dedicated fusion neutron source to enable them to proceed in an efficient and safe manner to reach their full mission and performance.