ActiveSupport::Testing::Isolation

# File activesupport/lib/active_support/testing/isolation.rb, line 18
      def self.forking_env?
        !ENV["NO_FORK"] && Process.respond_to?(:fork)
      end

# File activesupport/lib/active_support/testing/isolation.rb, line 22
      def run
        status, serialized = run_in_isolation do
          super
        end

        unless status&.success?
          error = SubprocessCrashed.new("Subprocess exited with an error: #{status.inspect}\noutput: #{serialized.inspect}")
          error.set_backtrace(caller)
          self.failures << Minitest::UnexpectedError.new(error)
          return defined?(Minitest::Result) ? Minitest::Result.from(self) : dup
        end

        Marshal.load(serialized)
      end