Tests for marks.

STARTTEST
:so small.vim
:" test that a deleted mark is restored after delete-undo-redo-undo
:/^\t/+1
:set nocp viminfo+=nviminfo
madduu
:let a = string(getpos("'a"))
:$put ='Mark after delete-undo-redo-undo: '.a
:''
ENDTEST

	textline A
	textline B
	textline C

STARTTEST
:" test that CTRL-A and CTRL-X updates last changed mark '[, '].
:/^123/
:execute "normal! \<C-A>`[v`]rAjwvjw\<C-X>`[v`]rX"
ENDTEST

CTRL-A CTRL-X:
123 123 123
123 123 123
123 123 123

STARTTEST
:g/^STARTTEST/.,/^ENDTEST/d
:wq! test.out
ENDTEST

Results: