diff --git a/src/testdir/shared.vim b/src/testdir/shared.vim
index cf15a4c..78f204c 100644
--- a/src/testdir/shared.vim
+++ b/src/testdir/shared.vim
@@ -325,3 +325,12 @@
   endif
   return 1
 endfunc
+
+func IsRoot()
+  if !has('unix')
+    return v:false
+  elseif $USER == 'root' || system('id -un') =~ '\<root\>'
+    return v:true
+  endif
+  return v:false
+endfunc