patch 8.2.2979: not all options code is covered by tests

Problem:    Not all options code is covered by tests.
Solution:   Add more tests for options. (Yegappan Lakshmanan, closes #8369)
diff --git a/src/testdir/test_help.vim b/src/testdir/test_help.vim
index ff2bc41..15cc642 100644
--- a/src/testdir/test_help.vim
+++ b/src/testdir/test_help.vim
@@ -123,5 +123,15 @@
   call delete('Xdir', 'rf')
 endfunc
 
+" Test for setting the 'helpheight' option in the help window
+func Test_help_window_height()
+  let &cmdheight = &lines - 24
+  set helpheight=10
+  help
+  set helpheight=14
+  call assert_equal(14, winheight(0))
+  set helpheight& cmdheight=1
+  close
+endfunc
 
 " vim: shiftwidth=2 sts=2 expandtab