patch 8.2.0342: some code in ex_getln.c not covered by tests

Problem:    Some code in ex_getln.c not covered by tests.
Solution:   Add more tests. (Yegappan Lakshmanan, closes #5717)
diff --git a/src/testdir/test_ex_mode.vim b/src/testdir/test_ex_mode.vim
index 91ba012..e88bdf5 100644
--- a/src/testdir/test_ex_mode.vim
+++ b/src/testdir/test_ex_mode.vim
@@ -49,6 +49,8 @@
     call assert_equal(['  foo', '    foo'],       Ex("    foo\<C-d>"), e)
     call assert_equal(['foo', '    foo0'],        Ex("    foo0\<C-d>"), e)
     call assert_equal(['foo', '    foo^'],        Ex("    foo^\<C-d>"), e)
+    call assert_equal(['foo', 'foo'],
+          \ Ex("\<BS>\<C-H>\<Del>foo"), e)
   endfor
 
   set sw&
@@ -128,4 +130,13 @@
   call assert_equal("a\rb", l)
 endfunc
 
+" Test for :append! command in Ex mode
+func Test_Ex_append()
+  new
+  call setline(1, "\t   abc")
+  call feedkeys("Qappend!\npqr\nxyz\n.\nvisual\n", 'xt')
+  call assert_equal(["\t   abc", "\t   pqr", "\t   xyz"], getline(1, '$'))
+  close!
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab