Before any test flight(s).
Before ANY test flight(s), as a simple member of the public I think it would be reasonable to see at least something along the following lines.
I understand that two of the first 787 airframes were written off.
I would expect one of these airframes to be fitted out with the new battery containment system, complete with its fully charged battery, with visible and infra-red cameras and video cameras both inside and outside the airframe.
On the ground, bring about the most sudden run-away possible in the battery and let the world see what happens.
Only after that should any test flight be permitted.
Safety is not concerned with any theory of how failure occurs, or with any statistics of probability of failure, but only with the consequences of a run-away, which someday, somewhere, will occur.
What argument could be put forward against this proposal?