Better categorize test coverage results

Also marks a few things as uncovered, and removes an unused class.

app/controllers/unicorn_test_controller.rb

+# :nocov:
 if Rails.env.test?
   class UnicornTestController < ActionController::Base
     def pid
@@ -10,3 +11,4 @@ if Rails.env.test?
     end
   end
 end
+# :nocov:

lib/file_streamer.rb

-class FileStreamer #:nodoc:
-  attr_reader :to_path
-
-  def initialize(path)
-    @to_path = path
-  end
-
-  # Stream the file's contents if Rack::Sendfile isn't present.
-  def each
-    File.open(to_path, 'rb') do |file|
-      while chunk = file.read(16384)
-        yield chunk
-      end
-    end
-  end
-end

lib/gitlab/middleware/webpack_proxy.rb

 # This Rack middleware is intended to proxy the webpack assets directory to the
 # webpack-dev-server.  It is only intended for use in development.
 
+# :nocov:
 module Gitlab
   module Middleware
     class WebpackProxy < Rack::Proxy
@@ -22,3 +23,4 @@ module Gitlab
     end
   end
 end
+# :nocov:

lib/gitlab/o_auth/session.rb

+# :nocov:
 module Gitlab
   module OAuth
     module Session
@@ -15,3 +16,4 @@ module Gitlab
     end
   end
 end
+# :nocov:

lib/gitlab/seeder.rb

+# :nocov:
 module DeliverNever
   def deliver_later
     self
@@ -21,3 +22,4 @@ module Gitlab
     end
   end
 end
+# :nocov:

spec/simplecov_env.rb

@@ -36,18 +36,25 @@ module SimpleCovEnv
       track_files '{app,lib}/**/*.rb'
 
       add_filter '/vendor/ruby/'
+      add_filter 'app/controllers/sherlock/'
       add_filter 'config/initializers/'
+      add_filter 'db/fixtures/'
+      add_filter 'lib/gitlab/sidekiq_middleware/'
+      add_filter 'lib/system_check/'
 
       add_group 'Controllers', 'app/controllers'
-      add_group 'Models', 'app/models'
-      add_group 'Mailers', 'app/mailers'
+      add_group 'Finders',     'app/finders'
       add_group 'Helpers',     'app/helpers'
-      add_group 'Workers', %w(app/jobs app/workers)
       add_group 'Libraries',   'lib'
+      add_group 'Mailers',     'app/mailers'
+      add_group 'Models',      'app/models'
+      add_group 'Policies',    'app/policies'
+      add_group 'Presenters',  'app/presenters'
+      add_group 'Serializers', 'app/serializers'
       add_group 'Services',    'app/services'
-      add_group 'Finders', 'app/finders'
       add_group 'Uploaders',   'app/uploaders'
       add_group 'Validators',  'app/validators'
+      add_group 'Workers',     %w(app/jobs app/workers)
 
       merge_timeout 365.days
     end