The MCDC paradox

Abstract

Modified Condition/Decision Coverage (MCDC) is a structural testing strategy required to verify Level A software used in commercial aviation. In DO-178B, Level A software is defined as software whose anomalous behavior would cause or contribute to a failure of system function resulting in a catastrophic failure condition for the aircraft. Paradoxically, this technique does not detect common errors, yet it consumes a large portion (approximately 25%) of the verification budget because of the number of test cases required to satisfy this coverage. Furthermore, this approach is directly applicable to only high-level languages, making its applicability of limited value to assembly language programs and machine-level code which could have been generated by auto code tools. A simpler approach is suggested in this paper that would better detect these common errors and would be more cost-effective for all applications.