我在RailsTutorial.org上遵循Ruby on Rails教程，在3.3.1节（/ book / static_pages＃cha-static_pages）上运行＆＃39; rails test＆＃39;首次。我按照建议使用Cloud9 IDE，据我所知，我已完全按照脚本进行操作。一切都符合这一点。
我还对错误进行了一些搜索，并对有关tmux的内容提出了意见，但我在Ruby on Rails或Cloud9上没有足够的经验来确定我正在做什么。有人还建议做捆绑执行耙试验＆＃39;作为替代，但我得到同样的错误：
2 runs, 2 assertions, 0 failures, 0 errors, 0 skips
/usr/local/rvm/gems/ruby-2.4.1/gems/notiffany-0.1.1/lib/notiffany/notifier/tmux/client.rb:12:in 'version': undefined method '[]' for nil:NilClass (NoMethodError)
from /usr/local/rvm/gems/ruby-2.4.1/gems/notiffany-0.1.1/lib/notiffany/notifier/tmux.rb:69:in '_check_available'
from /usr/local/rvm/gems/ruby-2.4.1/gems/notiffany-0.1.1/lib/notiffany/notifier/base.rb:59:in 'initialize'
from /usr/local/rvm/gems/ruby-2.4.1/gems/notiffany-0.1.1/lib/notiffany/notifier/detected.rb:100:in 'new'
from /usr/local/rvm/gems/ruby-2.4.1/gems/notiffany-0.1.1/lib/notiffany/notifier/detected.rb:100:in '_add'
from /usr/local/rvm/gems/ruby-2.4.1/gems/notiffany-0.1.1/lib/notiffany/notifier/detected.rb:62:in 'block (2 levels) in detect'
from /usr/local/rvm/gems/ruby-2.4.1/gems/notiffany-0.1.1/lib/notiffany/notifier/detected.rb:60:in 'each'
from /usr/local/rvm/gems/ruby-2.4.1/gems/notiffany-0.1.1/lib/notiffany/notifier/detected.rb:60:in 'detect'
from /usr/local/rvm/gems/ruby-2.4.1/gems/notiffany-0.1.1/lib/notiffany/notifier/detected.rb:60:in 'block in detect'
from /usr/local/rvm/gems/ruby-2.4.1/gems/notiffany-0.1.1/lib/notiffany/notifier/detected.rb:59:in 'each'
from /usr/local/rvm/gems/ruby-2.4.1/gems/notiffany-0.1.1/lib/notiffany/notifier/detected.rb:59:in 'detect'
from /usr/local/rvm/gems/ruby-2.4.1/gems/notiffany-0.1.1/lib/notiffany/notifier.rb:180:in '_detect_or_add_notifiers'
from /usr/local/rvm/gems/ruby-2.4.1/gems/notiffany-0.1.1/lib/notiffany/notifier.rb:198:in '_activate'
from /usr/local/rvm/gems/ruby-2.4.1/gems/notiffany-0.1.1/lib/notiffany/notifier.rb:87:in 'initialize'
from /usr/local/rvm/gems/ruby-2.4.1/gems/notiffany-0.1.1/lib/notiffany/notifier.rb:42:in 'new'
from /usr/local/rvm/gems/ruby-2.4.1/gems/notiffany-0.1.1/lib/notiffany/notifier.rb:42:in 'connect'
from /usr/local/rvm/gems/ruby-2.4.1/gems/guard-2.13.0/lib/guard/notifier.rb:11:in 'connect'
from /usr/local/rvm/gems/ruby-2.4.1/gems/guard-2.13.0/lib/guard/notifier.rb:31:in 'notify'
from /usr/local/rvm/gems/ruby-2.4.1/gems/guard-compat-1.2.1/lib/guard/compat/plugin.rb:113:in 'notify'
from /usr/local/rvm/gems/ruby-2.4.1/gems/guard-minitest-2.4.4/lib/guard/minitest/notifier.rb:31:in 'notify'
from /usr/local/rvm/gems/ruby-2.4.1/gems/guard-minitest-2.4.4/lib/guard/minitest/reporter.rb:10:in 'report'
from /usr/local/rvm/gems/ruby-2.4.1/gems/minitest-5.11.1/lib/minitest.rb:791:in 'each'
from /usr/local/rvm/gems/ruby-2.4.1/gems/minitest-5.11.1/lib/minitest.rb:791:in 'report'
from /usr/local/rvm/gems/ruby-2.4.1/gems/minitest-5.11.1/lib/minitest.rb:141:in 'run'
from /usr/local/rvm/gems/ruby-2.4.1/gems/minitest-5.11.1/lib/minitest.rb:63:in 'block in autorun'
我在Gemfile中看不到任何名为notiffany的内容，但我发现它与Guard有关。由于我使用的是教程中指定的特定版本，因此我不确定是否需要修复新版本。
我可能只是没有搜索到正确的关键字，所以如果以前已经回答过，我会道歉。任何帮助表示赞赏。
-Jay