fix broken guard list cmd and its spec

lib/guard/dsl_describer.rb

@@ -35,11 +35,13 @@ def initialize(options = {})
     # @see CLI#list
     #
     def list
+      _evaluate_guardfile
       names = ::Guard::PluginUtil.plugin_names.sort.uniq
       final_rows = names.inject([]) do |rows, name|
+        used = ::Guard.plugins(name).any?
         rows << {
           Plugin: name.capitalize,
-          Guardfile: ::Guard.plugins(name) ? "✔" : "✘"
+          Guardfile: used ? "✔" : "✘"
         }
       end
 

spec/lib/guard/dsl_describer_spec.rb

@@ -67,13 +67,15 @@
     end
 
     before do
+      stub_user_guard_rb
       allow(::Guard::PluginUtil).to receive(:plugin_names) do
         %w(test another even more)
       end
     end
 
     it "lists the available Guards declared as strings or symbols" do
       ::Guard::DslDescriber.new(guardfile_contents: guardfile).list
+      expect(@output).to eq result
     end
   end