instance method add_test

# File activesupport/lib/active_support/testing/parallelization/test_distributor.rb, line 87
        def add_test(test)
          @mutex.synchronize do
            return if @closed || !@queues

            worker_id = @next_worker
            @next_worker = (@next_worker + 1) % @worker_count
            queue = @queues[worker_id]
            queue << test unless queue.closed?
            @cv.signal  # Wake one waiting worker
          end
        end