> A better analogy might be for rockets / spaceflight-- where individual systems are rigorously tested independently, but a live launch is the only place that t

> A better analogy might be for rockets / spaceflight-- where individual systems are rigorously tested independently, but a live launch is the only place that they all come together and have to function as one tightly coupled system. I understand the point that you are trying to make, but your analogy is a bit poorly chosen. Speaking from my days as a sounding rocket telemetry engineer, we performed lots of tests of the individual systems, as you say. But then we also put everything together and performed several "sequence tests" where the entire vehicle (minus the motor) was assembled and tested as if the countdown were real. All events were triggered as if the vehicle were in flight, and experiment systems were tested to ensure they would power on as expected and provide real data. If we had any deployables, the deployment mechanism would be tested to the maximum extent possible. These sequence tests happened off the rail (in special testing facilities) and on the rail (fully assembled in launch configuration, with a motor). Basically, if you wait until the actual launch to perform integration tests of all of this, you WILL fail. There are too many pieces that need to function in concert to expect them to all work without integration testing.