A Composite structure does not mean that the structure is biult without an alloy base. New fuselage construction involves layering alluminiums between layers of a fibre sandwich. This allows a thinner aluminium structure, hence less weight but a stronger bonded structurer.
The actual procedure for inspecting for lightening strikes is not available yet.
Given the amount of testing that goes into any new aircraft, pioneered by Boeing, you can be assured that this question has been addressed.