Depends - as it's designed (using GRC's Paramarine - http://www.qinetiq.com/what/capabilities/maritime/Pages/naval-architecture-design-analysis.aspx http://www.

Depends - as it's designed (using GRC's Paramarine - http://www.qinetiq.com/what/capabilities/maritime/Pages/naval-architecture-design-analysis.aspx http://www.qinetiq.com/what/capabilities/maritime/Pages/nava...) you can virtually unit test things like propulsion, stability and buoyancy. Once it's been assembled into one complete system, it's very difficult to do that - individual systems on-board from a systems perspective could be unit tested, but actual physical items - not so much - generally they only find out about mismatches when they try and assemble the warship/sub from different sections (sometimes built by different companies) and they discover their tolerances were off.