Simplify Cask `spec_helper`.

Library/Homebrew/cask/lib/hbc/locations.rb

@@ -15,6 +15,8 @@ module Hbc
         @default_caskroom ||= HOMEBREW_PREFIX.join("Caskroom")
       end
 
+      attr_writer :caskroom
+
       def caskroom
         @caskroom ||= begin
           if Utils.path_occupied?(legacy_caskroom)
@@ -36,14 +38,12 @@ module Hbc
         end
       end
 
-      def caskroom=(caskroom)
-        @caskroom = caskroom
-      end
-
       def legacy_cache
         @legacy_cache ||= HOMEBREW_CACHE.join("Casks")
       end
 
+      attr_writer :cache
+
       def cache
         @cache ||= HOMEBREW_CACHE.join("Cask")
       end

Library/Homebrew/cask/spec/spec_helper.rb

-require "pathname"
 require "rspec/its"
 require "rspec/wait"
 
@@ -22,9 +21,6 @@ Pathname.glob(HOMEBREW_LIBRARY_PATH.join("cask", "spec", "support", "**", "*.rb"
 require "hbc"
 
 # create and override default directories
-Hbc.appdir = Pathname.new(TEST_TMPDIR).join("Applications").tap(&:mkpath)
-Hbc.cache.mkpath
-Hbc.caskroom = Hbc.default_caskroom.tap(&:mkpath)
 Hbc.default_tap = Tap.fetch("caskroom", "spec").tap do |tap|
   # link test casks
   FileUtils.mkdir_p tap.path.dirname
@@ -37,6 +33,7 @@ FileUtils.ln_s Pathname.new(ENV["HOMEBREW_LIBRARY"]).join("Taps", "caskroom", "h
 HOMEBREW_CASK_DIRS = [
   :appdir,
   :caskroom,
+  :cache,
   :prefpanedir,
   :qlplugindir,
   :servicedir,