The mechanical testing in heavy liquid metals is performed in order to obtain information about the influence of the liquid metal on Generation IV candidate construction materials. For testing in heavy liquid metal environment, it is required to test comparably with standards of mechanical testing in air at high temperatures. The paper summarizes the approach to the measurement of mechanical properties in such environment. Potential issues of force and deformation measurement are analyzed on examples of specific use in the project aimed on static fracture toughness testing in liquid lead. Technical solutions (e.g. extensometer and steel bellows) are discussed and suggested based on previous experimental experience.