Solder low-cycle fatigue damage caused by temperature changes is one major reliability concern in electronics. In the paper, two fundamental approaches to characterize the solder joint fatigue resistance are introduced: testing and theoretical modelling. Thermal test cycling, which is applied to the majority of electronic products, is discussed in more detail and reference to different standards is made. Additionally, theoretical modelling based on analytical estimates as well as on numerical models, i.e. finite element models, is briefly introduced.