Here’s an interesting interview with Lori Garver, Deputy Administrator of NASA during early SLS development.
From the interview:
“I think a test flight is just that, it’s a test flight. This happy talk of it being completed—just look at the language, the celebration, NASA’s planning, and so forth for the launch. There is not another test flight planned if this doesn’t go perfectly. So then what? You’re going to put people on one in two years if the first one didn’t go well? I just have never heard anyone talk about that plan.”
This is exactly what I’ve been wondering about. SpaceX moves forward by crashing lots of rockets. I know NASA works differently, but surely you have to plan for failure in your test schedule.