> do they run unit tests on those My initial glib answer is “no, the engineers are stuck to deal with the bad design afterwards” :) My less glib answer would

> do they run unit tests on those My initial glib answer is “no, the engineers are stuck to deal with the bad design afterwards” :) My less glib answer would be that most disciplines of engineering do do modelling and “virtual testing”. I’ve been working on largish drones for about 18 months. Electronics get specced out, circuits get drawn and simulated, currents are estimated and components are specced based on those estimates, etc. On the mechanical side, parts are drawn in CAD, analyzed for proper fit and assemble-ability, FEA is used to determine whether a part is likely to be strong enough for the static and dynamic loads that will be placed on the aircraft, etc. All of this happens, generally, before circuit boards or modules get ordered or before the first chunk of aluminum goes into the CNC. As far as building software goes, I’ve recently had to start digging into DO-178C, and I’m pretty impressed so far. Despite having been through engineering school (EE), I haven’t ever really had to put this level of rigour into practice for software before. It feels slow and somewhat time consuming, but I’m feeling more and more confident that the module I’m working on is going to be pretty damned robust. It’s not a “certification required” unit, but it would be a huge pain in the ass if it failed and couldn’t recover without human intervention; as a result I’m doing more of a “DO-178C lite” with detailed low-level requirements stated explicitly, system architecture drawn out first, sequence diagrams for the complicated event-driven parts, state charts for the different parallel systems, etc.