new file mode 100644
--- /dev/null
+++ b/src/testdir/test_comments.vim
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+" Tests for the various flags in the 'comments' option
+
+" Test for the 'n' flag in 'comments'
+func Test_comment_nested()
+  new
+  setlocal comments=n:> fo+=ro
+  exe "normal i> B\nD\<C-C>ggOA\<C-C>joC\<C-C>Go\<BS>>>> F\nH"
+  exe "normal 5GOE\<C-C>6GoG"
+  let expected =<< trim END
+    > A
+    > B
+    > C
+    > D
+    >>>> E
+    >>>> F
+    >>>> G
+    >>>> H
+  END
+  call assert_equal(expected, getline(1, '$'))
+  close!
+endfunc
+
+" Test for the 'b' flag in 'comments'
+func Test_comment_blank()
+  new
+  setlocal comments=b:* fo+=ro
+  exe "normal i* E\nF\n\<BS>G\nH\<C-C>ggOC\<C-C>O\<BS>B\<C-C>OA\<C-C>2joD"
+  let expected =<< trim END
+    A
+    *B
+    * C
+    * D
+    * E
+    * F
+    *G
+    H
+  END
+  call assert_equal(expected, getline(1, '$'))
+  close!
+endfunc
+
+" Test for the 'f' flag in 'comments' (only the first line has a comment
+" string)
+func Test_comment_firstline()
+  new
+  setlocal comments=f:- fo+=ro
+  exe "normal i- B\nD\<C-C>ggoC\<C-C>ggOA\<C-C>"
+  call assert_equal(['A', '- B', '  C', '  D'], getline(1, '$'))
+  %d
+  setlocal comments=:-
+  exe "normal i- B\nD\<C-C>ggoC\<C-C>ggOA\<C-C>"
+  call assert_equal(['- A', '- B', '- C', '- D'], getline(1, '$'))
+  close!
+endfunc
+
+" Test for the 's', 'm' and 'e' flags in 'comments'
+" Test for automatically adding comment leaders in insert mode
+func Test_comment_threepiece()
+  new
+  setlocal expandtab
+  call setline(1, ["\t/*"])
+  setlocal formatoptions=croql
+  call cursor(1, 3)
+  call feedkeys("A\<cr>\<cr>/", 'tnix')
+  call assert_equal(["\t/*", " *", " */"], getline(1, '$'))
+
+  " If a comment ends in a single line, then don't add it in the next line
+  %d
+  call setline(1, '/* line1 */')
+  call feedkeys("A\<CR>next line", 'xt')
+  call assert_equal(['/* line1 */', 'next line'], getline(1, '$'))
+
+  %d
+  " Copy the trailing indentation from the leader comment to a new line
+  setlocal autoindent noexpandtab
+  call feedkeys("a\t/*\tone\ntwo\n/", 'xt')
+  call assert_equal(["\t/*\tone", "\t *\ttwo", "\t */"], getline(1, '$'))
+  close!
+endfunc
+
+" Test for the 'r' flag in 'comments' (right align comment)
+func Test_comment_rightalign()
+  new
+  setlocal comments=sr:/***,m:**,ex-2:******/ fo+=ro
+  exe "normal i=\<C-C>o\t  /***\nD\n/"
+  exe "normal 2GOA\<C-C>joB\<C-C>jOC\<C-C>joE\<C-C>GOF\<C-C>joG"
+  let expected =<< trim END
+    =
+    A
+    	  /***
+    	    ** B
+    	    ** C
+    	    ** D
+    	    ** E
+    	    **     F
+    	    ******/
+    G
+  END
+  call assert_equal(expected, getline(1, '$'))
+  close!
+endfunc
+
+" Test for the 'O' flag in 'comments'
+func Test_comment_O()
+  new
+  setlocal comments=Ob:* fo+=ro
+  exe "normal i* B\nD\<C-C>kOA\<C-C>joC"
+  let expected =<< trim END
+    A
+    * B
+    * C
+    * D
+  END
+  call assert_equal(expected, getline(1, '$'))
+  close!
+endfunc
+
+" Test for using a multibyte character as a comment leader
+func Test_comment_multibyte_leader()
+  new
+  let t =<< trim END
+    {
+    Ｘ
+    Ｘa
+    ＸaＹ
+    ＸＹ
+    ＸＹＺ
+    Ｘ Ｙ
+    Ｘ ＹＺ
+    ＸＸ
+    ＸＸa
+    ＸＸＹ
+    }
+  END
+  call setline(1, t)
+  call cursor(2, 1)
+
+  set tw=2 fo=cqm comments=n:Ｘ
+  exe "normal gqgqjgqgqjgqgqjgqgqjgqgqjgqgqjgqgqjgqgqjgqgqjgqgq"
+  let t =<< trim END
+    Ｘ
+    Ｘa
+    ＸaＹ
+    ＸＹ
+    ＸＹＺ
+    Ｘ Ｙ
+    Ｘ ＹＺ
+    ＸＸ
+    ＸＸa
+    ＸＸＹ
+  END
+  exe "normal o\n" . join(t, "\n")
+
+  let expected =<< trim END
+    {
+    Ｘ
+    Ｘa
+    Ｘa
+    ＸＹ
+    ＸＹ
+    ＸＹ
+    ＸＺ
+    Ｘ Ｙ
+    Ｘ Ｙ
+    Ｘ Ｚ
+    ＸＸ
+    ＸＸa
+    ＸＸＹ
+
+    Ｘ
+    Ｘa
+    Ｘa
+    ＸＹ
+    ＸＹ
+    ＸＹ
+    ＸＺ
+    Ｘ Ｙ
+    Ｘ Ｙ
+    Ｘ Ｚ
+    ＸＸ
+    ＸＸa
+    ＸＸＹ
+    }
+  END
+  call assert_equal(expected, getline(1, '$'))
+
+  set tw& fo& comments&
+  close!
+endfunc
+
+" Test for a space character in 'comments' setting
+func Test_comment_space()
+  new
+  setlocal comments=b:\ > fo+=ro
+  exe "normal i> B\nD\<C-C>ggOA\<C-C>joC"
+  exe "normal Go > F\nH\<C-C>kOE\<C-C>joG"
+  let expected =<< trim END
+    A
+    > B
+    C
+    D
+     > E
+     > F
+     > G
+     > H
+  END
+  call assert_equal(expected, getline(1, '$'))
+  close!
+endfunc
+
+" Test for formatting lines with and without comments
+func Test_comment_format_lines()
+  new
+  call setline(1, ['one', '/* two */', 'three'])
+  normal gggqG
+  call assert_equal(['one', '/* two */', 'three'], getline(1, '$'))
+  close!
+endfunc
+
+" Test for using 'a' in 'formatoptions' with comments
+func Test_comment_autoformat()
+  new
+  setlocal formatoptions+=a
+  call feedkeys("a- one\n- two\n", 'xt')
+  call assert_equal(['- one', '- two', ''], getline(1, '$'))
+
+  %d
+  call feedkeys("a\none\n", 'xt')
+  call assert_equal(['', 'one', ''], getline(1, '$'))
+
+  setlocal formatoptions+=aw
+  %d
+  call feedkeys("aone \ntwo\n", 'xt')
+  call assert_equal(['one two', ''], getline(1, '$'))
+
+  %d
+  call feedkeys("aone\ntwo\n", 'xt')
+  call assert_equal(['one', 'two', ''], getline(1, '$'))
+
+  close!
+endfunc
+
+" Test for joining lines with comments ('j' flag in 'formatoptions')
+func Test_comment_join_lines_fo_j()
+  new
+  setlocal fo+=j comments=://
+  call setline(1, ['i++; // comment1', '           // comment2'])
+  normal J
+  call assert_equal('i++; // comment1 comment2', getline(1))
+  setlocal fo-=j
+  call setline(1, ['i++; // comment1', '           // comment2'])
+  normal J
+  call assert_equal('i++; // comment1 // comment2', getline(1))
+  " Test with nested comments
+  setlocal fo+=j comments=n:>,n:)
+  call setline(1, ['i++; > ) > ) comment1', '           > ) comment2'])
+  normal J
+  call assert_equal('i++; > ) > ) comment1 comment2', getline(1))
+  close!
+endfunc
+
+" Test for formatting lines where only the first line has a comment.
+func Test_comment_format_firstline_comment()
+  new
+  setlocal formatoptions=tcq
+  call setline(1, ['- one two', 'three'])
+  normal gggqG
+  call assert_equal(['- one two three'], getline(1, '$'))
+
+  %d
+  call setline(1, ['- one', '- two'])
+  normal gggqG
+  call assert_equal(['- one', '- two'], getline(1, '$'))
+  close!
+endfunc
+
+" vim: shiftwidth=2 sts=2 expandtab