The general planning procedure for development testing at the author's firm is outlined. Strains in static tests of cast iron components under loads simulating service conditions are surveyed by brittle coatings and measured by strain gauges with incremental and shake‐down load application. The fatigue life is then estimated in a novel manner by reference to the S/N curves established by Deere in push‐pull tests on various cast irons. For nonzero mean strains, reference is also made to the static stress‐strain curves for the tested material and to its Goodman diagram so that an equivalent strain reversal can be deduced and the Deere curve applied. For varying loads Miner's rule is in