Answer:
Test the working prototype
Step-by-step explanation:
After the prototype is built, it is put through basic operational tests and purpose of applicability or performance test
The prototype is also laboratory tested to determine how reliable it is with tests performed to determine the modes of failure. Performance of tests are carried out by subjecting the prototype to stresses beyond its designed stress such as to discover failure modes
The system is however tested in isolation at this stage and the performance and risks of the prototype are quantified after the test, with improvement requirement outlined for modification of the design.