This International Standard gives guidance for reliability growth during final testing or acceptance testing of unique complex systems. It gives guidance on accelerated test conditions and criteria for stopping these tests. “Unique” means that no information exists on similar systems, and the small number of produced systems means that information deducted from the test has limited use for future production. This standard concerns reliability growth of repairable complex systems consisting of hardware with embedded software. It can be used for describing the procedure for acceptance testing, "running-in", and to ensure that reliability of a delivered system is not compromised by coding errors, workmanship errors or manufacturing errors. It only covers the early failure period of the system life cycle and neither the constant failure period, nor the wear out failure period. It can also be used when a company wants to optimize the duration of internal production testing during manufacturing of prototypes, single systems or small series. It is applicable mainly to large hardware/software systems, but does not cover large networks, for example telecommunications and power networks, since new parts of such systems cannot usually be isolated during the testing.