【Ruby on Railsチュートリアル】rails testでエラーが出ます

Question

AWS、Cloud9でRuby on Railsチュートリアルを勉強中です。

第3章で初めてテストを行うのですが、
以下のように入力すると

rails test

下のようなエラーが返りました

Running via Spring preloader in process 12239
Run options: --seed 33311

# Running:

..

Finished in 0.333246s, 6.0016 runs/s, 6.0016 assertions/s.

2 runs, 2 assertions, 0 failures, 0 errors, 0 skips
Traceback (most recent call last):
        33: from -e:1:in `<main>'
        32: from /home/ec2-user/.rvm/rubies/ruby-2.6.0/lib/ruby/2.6.0/rubygems/core_ext/kernel_require.rb:54:in `require'
        31: from /home/ec2-user/.rvm/rubies/ruby-2.6.0/lib/ruby/2.6.0/rubygems/core_ext/kernel_require.rb:54:in `require'
        30: from /home/ec2-user/.rvm/gems/ruby-2.6.0/gems/spring-2.0.2/lib/spring/application/boot.rb:19:in `<top (required)>'
        29: from /home/ec2-user/.rvm/gems/ruby-2.6.0/gems/spring-2.0.2/lib/spring/application.rb:135:in `run'
        28: from /home/ec2-user/.rvm/gems/ruby-2.6.0/gems/spring-2.0.2/lib/spring/application.rb:135:in `loop'
        27: from /home/ec2-user/.rvm/gems/ruby-2.6.0/gems/spring-2.0.2/lib/spring/application.rb:141:in `block in run'
        26: from /home/ec2-user/.rvm/gems/ruby-2.6.0/gems/spring-2.0.2/lib/spring/application.rb:171:in `serve'
        25: from /home/ec2-user/.rvm/gems/ruby-2.6.0/gems/spring-2.0.2/lib/spring/application.rb:171:in `fork'
        24: from /home/ec2-user/.rvm/gems/ruby-2.6.0/gems/minitest-5.10.3/lib/minitest.rb:63:in `block in autorun'
        23: from /home/ec2-user/.rvm/gems/ruby-2.6.0/gems/minitest-5.10.3/lib/minitest.rb:141:in `run'
        22: from /home/ec2-user/.rvm/gems/ruby-2.6.0/gems/minitest-5.10.3/lib/minitest.rb:687:in `report'
        21: from /home/ec2-user/.rvm/gems/ruby-2.6.0/gems/minitest-5.10.3/lib/minitest.rb:687:in `each'
        20: from /home/ec2-user/.rvm/gems/ruby-2.6.0/gems/guard-minitest-2.4.4/lib/guard/minitest/reporter.rb:10:in `report'
        19: from /home/ec2-user/.rvm/gems/ruby-2.6.0/gems/guard-minitest-2.4.4/lib/guard/minitest/notifier.rb:31:in `notify'
        18: from /home/ec2-user/.rvm/gems/ruby-2.6.0/gems/guard-compat-1.2.1/lib/guard/compat/plugin.rb:113:in `notify'
        17: from /home/ec2-user/.rvm/gems/ruby-2.6.0/gems/guard-2.13.0/lib/guard/notifier.rb:31:in `notify'
        16: from /home/ec2-user/.rvm/gems/ruby-2.6.0/gems/guard-2.13.0/lib/guard/notifier.rb:11:in `connect'
        15: from /home/ec2-user/.rvm/gems/ruby-2.6.0/gems/notiffany-0.1.1/lib/notiffany/notifier.rb:42:in `connect'
        14: from /home/ec2-user/.rvm/gems/ruby-2.6.0/gems/notiffany-0.1.1/lib/notiffany/notifier.rb:42:in `new'
        13: from /home/ec2-user/.rvm/gems/ruby-2.6.0/gems/notiffany-0.1.1/lib/notiffany/notifier.rb:87:in `initialize'
        12: from /home/ec2-user/.rvm/gems/ruby-2.6.0/gems/notiffany-0.1.1/lib/notiffany/notifier.rb:198:in `_activate'
        11: from /home/ec2-user/.rvm/gems/ruby-2.6.0/gems/notiffany-0.1.1/lib/notiffany/notifier.rb:180:in `_detect_or_add_notifiers'
        10: from /home/ec2-user/.rvm/gems/ruby-2.6.0/gems/notiffany-0.1.1/lib/notiffany/notifier/detected.rb:59:in `detect'
         9: from /home/ec2-user/.rvm/gems/ruby-2.6.0/gems/notiffany-0.1.1/lib/notiffany/notifier/detected.rb:59:in `each'
         8: from /home/ec2-user/.rvm/gems/ruby-2.6.0/gems/notiffany-0.1.1/lib/notiffany/notifier/detected.rb:60:in `block in detect'
         7: from /home/ec2-user/.rvm/gems/ruby-2.6.0/gems/notiffany-0.1.1/lib/notiffany/notifier/detected.rb:60:in `detect'
         6: from /home/ec2-user/.rvm/gems/ruby-2.6.0/gems/notiffany-0.1.1/lib/notiffany/notifier/detected.rb:60:in `each'
         5: from /home/ec2-user/.rvm/gems/ruby-2.6.0/gems/notiffany-0.1.1/lib/notiffany/notifier/detected.rb:62:in `block (2 levels) in detect'
         4: from /home/ec2-user/.rvm/gems/ruby-2.6.0/gems/notiffany-0.1.1/lib/notiffany/notifier/detected.rb:100:in `_add'
         3: from /home/ec2-user/.rvm/gems/ruby-2.6.0/gems/notiffany-0.1.1/lib/notiffany/notifier/detected.rb:100:in `new'
         2: from /home/ec2-user/.rvm/gems/ruby-2.6.0/gems/notiffany-0.1.1/lib/notiffany/notifier/base.rb:59:in `initialize'
         1: from /home/ec2-user/.rvm/gems/ruby-2.6.0/gems/notiffany-0.1.1/lib/notiffany/notifier/tmux.rb:69:in `_check_available'
/home/ec2-user/.rvm/gems/ruby-2.6.0/gems/notiffany-0.1.1/lib/notiffany/notifier/tmux/client.rb:12:in `version': undefined method `[]' for nil:NilClass (NoMethodError)

railsアプリは以下のように作成しました

rails _5.1.6_ new sample_app

チュートリアルと同じ内容ですがGemfile

source 'https://rubygems.org'

gem 'rails',        '5.1.6'
gem 'puma',         '3.9.1'
gem 'sass-rails',   '5.0.6'
gem 'uglifier',     '3.2.0'
gem 'coffee-rails', '4.2.2'
gem 'jquery-rails', '4.3.1'
gem 'turbolinks',   '5.0.1'
gem 'jbuilder',     '2.7.0'

group :development, :test do
  gem 'sqlite3', '1.3.13'
  gem 'byebug',  '9.0.6', platform: :mri
end

group :development do
  gem 'web-console',           '3.5.1'
  gem 'listen',                '3.1.5'
  gem 'spring',                '2.0.2'
  gem 'spring-watcher-listen', '2.0.1'
end

group :test do
  gem 'rails-controller-testing', '1.0.2'
  gem 'minitest',                 '5.10.3'
  gem 'minitest-reporters',       '1.1.14'
  gem 'guard',                    '2.13.0'
  gem 'guard-minitest',           '2.4.4'
end

group :production do
  gem 'pg', '0.20.0'
end

# Windows環境ではtzinfo-dataというgemを含める必要があります
gem 'tzinfo-data', platforms: [:mingw, :mswin, :x64_mingw, :jruby]

分かる方教えていただけないでしょうか。

Answer 1

同じ現象、解決法が見つかりました。

https://ty-engineer.com/ruby-on-rails/rails-tutorial-3-error-tmux/#rais_test

有難う御座いました。