Stop writing a test file in real world usage in some cases

test/test_ale_fix.vader

@@ -82,6 +82,8 @@ After:
   call ale#fix#registry#ResetToDefaults()
   call ale#linter#Reset()
 
+  setlocal buftype=nofile
+
   if filereadable('fix_test_file')
     call delete('fix_test_file')
   endif
@@ -245,6 +247,9 @@ Execute(ALEFix should save files on the save event):
 
   let g:ale_fixers.testft = ['AddDollars']
 
+  " We have to set the buftype to empty so the file will be written.
+  setlocal buftype=
+
   call SetUpLinters()
   call ale#events#SaveEvent(bufnr(''))