patch 8.2.0482: channel and sandbox code not sufficiently tested

Problem:    Channel and sandbox code not sufficiently tested.
Solution:   Add more tests. (Yegappan Lakshmanan, closes #5855)

src/testdir/test_visual.vim

@@ -267,6 +267,15 @@ func Test_virtual_replace2()
   call assert_equal(['abcd',
         \ 'efgh',
         \ 'ijkl'], getline(1, '$'))
+
+  " Test for truncating spaces in a newly added line using 'autoindent' if
+  " characters are not added to that line.
+  %d_
+  call setline(1, ['    app', '    bee', '    cat'])
+  setlocal autoindent
+  exe "normal gg$gRt\n\nr"
+  call assert_equal(['    apt', '', '    rat'], getline(1, '$'))
+
   " clean up
   %d_
   set bs&vim