class SimpleCov::ParallelAdapters::ParallelTestsAdapter

def ensure_loaded

off). See #1018.
`SimpleCov.parallel_tests true` (force on) or `false` (force
it. Users who want to override the auto-detect can set
parallel_tests" — silently skip and let GenericAdapter handle
convention), so a missing gem is treated as "user isn't using
the parallel_rspec gem which intentionally mirrors the env-var
for other reasons (custom subprocess coordination, CI sharding,
and `TEST_ENV_NUMBER` / `PARALLEL_TEST_GROUPS` are commonly set
optional dependency (see https://github.com/grosser/parallel_tests/issues/772),
`defined?(::ParallelTests)` downstream. parallel_tests is an
vars it sets are present, so callers can rely on
Auto-require `parallel_tests` when it's installed AND the env 
def ensure_loaded
  return if defined?(::ParallelTests) # simplecov:disable — only true after a previous load
  return if SimpleCov.parallel_tests == false # simplecov:disable — only fires when user opts out
  # simplecov:disable — env-var-only path
  return unless SimpleCov.parallel_tests || env_suggests_parallel_tests?
  # simplecov:disable — only fires under a real parallel_tests setup
  require "parallel_tests"
rescue LoadError
  # Gem isn't installed; stay quiet — warning here regressed
  # users who use those env vars for their own subprocess
  # coordination.
  # simplecov:enable
end