diff --git a/src/testdir/test_functions.vim b/src/testdir/test_functions.vim
index 6e54095..1c463f0 100644
--- a/src/testdir/test_functions.vim
+++ b/src/testdir/test_functions.vim
@@ -475,6 +475,11 @@
   call assert_equal('./file',      simplify('./dir/../file'))
   call assert_equal('../dir/file', simplify('dir/../../dir/file'))
   call assert_equal('./file',      simplify('dir/.././file'))
+  call assert_equal('../dir',      simplify('./../dir'))
+  call assert_equal('..',          simplify('../testdir/..'))
+  call mkdir('Xdir')
+  call assert_equal('.',           simplify('Xdir/../.'))
+  call delete('Xdir', 'd')
 
   call assert_fails('call simplify({->0})', 'E729:')
   call assert_fails('call simplify([])', 'E730:')