It is not the purpose, or possible, within the scope of this book to provide a detailed step-by-step guide on the procedures to be followed when conducting development and type testing of switchgear. Indeed, such a guide would run into several volumes and, due to detailed changes in specifications that take place from time to time, it would quickly become obsolete. It would also have to cover all types of switchgear including circuit breakers, switches, fuse switches, fuses, earth switches and disconnectors. However, the intention here is to give an overview of the important stages in testing that have to be completed in order to provide switchgear that is safe and able to operate correctly in the circuits and ambient conditions for which it is intended. By way of example, particular reference will be made to circuit breakers. The opportunity will be taken to highlight certain aspects of each type test in order to show the relative importance and the way in which solutions to encountered problems can, and usually will, have an influence on the performance of other type tests.