patch 8.2.1022: various parts of code not covered by tests

Problem:    Various parts of code not covered by tests.
Solution:   Add more tests. (Yegappan Lakshmanan, closes #6300)
diff --git a/src/testdir/test_textformat.vim b/src/testdir/test_textformat.vim
index 33daaab..d529b85 100644
--- a/src/testdir/test_textformat.vim
+++ b/src/testdir/test_textformat.vim
@@ -1116,6 +1116,20 @@
   call feedkeys("iabc abc a abc\<Esc>k0weade", 'xt')
   call assert_equal(['abc abcde ', 'a abc'], getline(1, '$'))
 
+  " when a line ends with space, it is not broken up.
+  %d
+  call feedkeys("ione two to    ", 'xt')
+  call assert_equal('one two to    ', getline(1))
+
+  " when a line ends with spaces and backspace is used in the next line, the
+  " last space in the previous line should be removed.
+  %d
+  set backspace=indent,eol,start
+  call setline(1, ['one    ', 'two'])
+  exe "normal 2Gi\<BS>"
+  call assert_equal(['one   two'], getline(1, '$'))
+  set backspace&
+
   " Test for 'a', 'w' and '1' options.
   setlocal textwidth=0
   setlocal fo=1aw