class Inspec::Formatters::RspecJson

def format_example(example)

either explicitly specified or auto-generated by rspec itself.
rspec's example id here corresponds to an inspec test's control name -

See https://github.com/rspec/rspec-core/blob/master/lib/rspec/core/formatters/json_formatter.rb
and dump_profile (both of which call format_example).
This is to avoid having to repeat this id functionality in both dump_summary
We are cheating and overriding a private method in RSpec's core JsonFormatter. 
def format_example(example)
  res = super(example)
  res[:id] = example.metadata[:id]
  res
end