For "WikiControllerTest#test_update_with_deleted_attachment_ids":https://www.redmine.org/projects/redmine/repository/entry/trunk/test/functional/wiki_controller_test.rb#L469 and "WikiControllerTest#test_update_with_deleted_attachment_ids_and_failure_should_preserve_selected_attachments":https://www.redmine.org/projects/redmine/repository/entry/trunk/test/functional/wiki_controller_test.rb#L488 , the files under test/fixtures/files/ may be deleted depending on the test execution order.
Need to call @set_tmp_attachments_directory@ as follows.

diff --git a/test/functional/wiki_controller_test.rb b/test/functional/wiki_controller_test.rb
index e3ac6cb4e..70b892ba5 100644
--- a/test/functional/wiki_controller_test.rb
+++ b/test/functional/wiki_controller_test.rb
@@ -467,6 +467,7 @@ class WikiControllerTest < Redmine::ControllerTest
   end

   def test_update_with_deleted_attachment_ids
+    set_tmp_attachments_directory
     @request.session[:user_id] = 2
     page = WikiPage.find(4)
     attachment = page.attachments.first
@@ -486,6 +487,7 @@ class WikiControllerTest < Redmine::ControllerTest
   end

   def test_update_with_deleted_attachment_ids_and_failure_should_preserve_selected_attachments
+    set_tmp_attachments_directory
     @request.session[:user_id] = 2
     page = WikiPage.find(4)
     attachment = page.attachments.first