patch 8.0.0032
Problem:    Tests may change the input file when something goes wrong.
Solution:   Avoid writing the input file.
diff --git a/src/testdir/test_tabpage.vim b/src/testdir/test_tabpage.vim
index 4bee795..3f69fb9 100644
--- a/src/testdir/test_tabpage.vim
+++ b/src/testdir/test_tabpage.vim
@@ -11,6 +11,7 @@
   0tabnew
   1tabnew
   $tabnew
+  %del
   tabdo call append(line('$'), tabpagenr())
   tabclose! 2
   tabrewind