class SimpleCov::ParallelAdapters::ParallelTestsAdapter

empty string).
`TEST_ENV_NUMBER` is "" and `first_process?` tests for that
handles `PARALLEL_TEST_GROUPS=1` naturally (the only worker's
side avoids the cross-process deadlock #922 reported. Also
overwhelmingly waits in the first process — picking the same
`wait_for_other_processes_to_finish` in an `RSpec.after(:suite)`
finishes" hooks, so user code that has its own
`first_process?` for "do something once after every worker
not the last. The parallel_tests README recommends
Pick the *first* started process to do the final-result work,

def first_worker?
  ::ParallelTests.first_process?
end