utc may months later i have also used test driven development and noticed that even a few representative tests can be used to detect problems it was not necessary to have complete test coverage of all functions just a few limited tests would provide a sanity check to the usability of the unit in general the limited tests approach reduces the amount of test cases that must be updated if the unit changes significantly although it could be argued that more tests would provide more protection reliability in the future and pay for themselves even when needing to be updated to match significant changes dr deming advocated a return to mass inspection to handle extreme safety concerns may