test fail of actor_spec

[himrock922]

Hi.
I did execute Rspec to use this gem.
But... actor_spec failed because the following error happend.

%  bundle exec rspec spec/celluloid/io/actor_spec.rb

(skip)
 100) Celluloid::IO behaves like a Celluloid Actor raw message sends logs on unhandled messages
       Failure/Error: Thread.current[:celluloid_actor_system] || @actor_system || raise(Error, "Celluloid is not yet started; use Celluloid.boot")
       
       Celluloid::Error:
         Celluloid is not yet started; use Celluloid.boot
       Shared Example Group: "a Celluloid Actor" called from ./spec/celluloid/io/actor_spec.rb:4

All error output of above wording.
Before I running the test, I added following to the spec_helper.rb

+ require "rspec/retry"
require "celluloid/rspec"

What is this error?

Regards.