patch 8.2.0261: some code not covered by tests

Problem:    Some code not covered by tests.
Solution:   Add test cases. (Yegappan Lakshmanan, closes #5645)
diff --git a/src/testdir/test_fileformat.vim b/src/testdir/test_fileformat.vim
index 394c274..efc5a0d 100644
--- a/src/testdir/test_fileformat.vim
+++ b/src/testdir/test_fileformat.vim
@@ -276,3 +276,23 @@
   call delete('XXUxDsMc')
   call delete('Xtest')
 endfunc
+
+" Test for changing the fileformat using ++read
+func Test_fileformat_plusplus_read()
+  new
+  call setline(1, ['one', 'two', 'three'])
+  w ++ff=dos Xfile1
+  enew!
+  r ++fileformat=unix Xfile1
+  call assert_equal('unix', &fileformat)
+  3r ++edit Xfile1
+  call assert_equal('dos', &fileformat)
+  close!
+  call delete('Xfile1')
+  set fileformat&
+  call assert_fails('e ++fileformat Xfile1', 'E474:')
+  call assert_fails('e ++ff=abc Xfile1', 'E474:')
+  call assert_fails('e ++abc1 Xfile1', 'E474:')
+endfunc
+
+" vim: shiftwidth=2 sts=2 expandtab