patch 8.1.1336: some eval functionality is not covered by tests

Problem:    Some eval functionality is not covered by tests.
Solution:   Add a few more test cases. (Masato Nishihata, closes #4374)
diff --git a/src/testdir/test_cindent.vim b/src/testdir/test_cindent.vim
index 7c2c5e3..3b57360 100644
--- a/src/testdir/test_cindent.vim
+++ b/src/testdir/test_cindent.vim
@@ -102,4 +102,14 @@
   bw!
 endfunc
 
+func Test_cindent_func()
+  new
+  setlocal cindent
+  call setline(1, ['int main(void)', '{', 'return 0;', '}'])
+  call assert_equal(cindent(0), -1)
+  call assert_equal(cindent(3), &sw)
+  call assert_equal(cindent(line('$')+1), -1)
+  bwipe!
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab