“The NBC Clause of Article II must be tested.”
Would you demand that “shall not be infringed” be tested?
Bravo! That is precisely what is at risk if we seek the "opinion" of any court, let alone a USSC that is one vote from castrating the 2dA.
Neither NBC or the 2dA needs to be "tested" or "decided".
I would prefer that an apolitical U.S. History professor explain the terms to any who fail to understand the context in which they were used and the purpose for which they were used. Such is plain to most that are not politically bent on misconstruing the Constitution.