Tests: Dir.mktmpdir neatly wraps up tmpdir + join

test/service/disk_service_test.rb

-require "tmpdir"
 require "service/shared_service_tests"
 
 class ActiveStorage::Service::DiskServiceTest < ActiveSupport::TestCase

test/service/mirror_service_test.rb

-require "tmpdir"
 require "service/shared_service_tests"
 
 class ActiveStorage::Service::MirrorServiceTest < ActiveSupport::TestCase
   mirror_config = (1..3).map do |i|
     [ "mirror_#{i}",
       service: "Disk",
-      root: File.join(Dir.tmpdir, "active_storage_mirror_#{i}") ]
+      root: Dir.mktmpdir("active_storage_tests_mirror_#{i}") ]
   end.to_h
 
   config = mirror_config.merge \
     mirror:   { service: "Mirror", primary: 'primary', mirrors: mirror_config.keys },
-    primary:  { service: "Disk", root: File.join(Dir.tmpdir, "active_storage") }
+    primary:  { service: "Disk", root: Dir.mktmpdir("active_storage_tests_primary") }
 
   SERVICE = ActiveStorage::Service.configure :mirror, config
 

test/test_helper.rb

@@ -17,7 +17,8 @@
 
 
 require "active_storage/service/disk_service"
-ActiveStorage::Blob.service = ActiveStorage::Service::DiskService.new(root: File.join(Dir.tmpdir, "active_storage"))
+require "tmpdir"
+ActiveStorage::Blob.service = ActiveStorage::Service::DiskService.new(root: Dir.mktmpdir("active_storage_tests"))
 ActiveStorage::Service.logger = ActiveSupport::Logger.new(STDOUT)
 
 require "active_storage/verified_key_with_expiration"
@@ -47,4 +48,4 @@ class ActionController::TestCase
 require "global_id"
 GlobalID.app = "ActiveStorageExampleApp"
 ActiveRecord::Base.send :include, GlobalID::Identification
-SignedGlobalID.verifier = ActiveStorage::VerifiedKeyWithExpiration.verifier
\ No newline at end of file
+SignedGlobalID.verifier = ActiveStorage::VerifiedKeyWithExpiration.verifier