diff --git a/src/testdir/test_man.vim b/src/testdir/test_man.vim
new file mode 100644
index 0000000..f2c48a4
--- /dev/null
+++ b/src/testdir/test_man.vim
@@ -0,0 +1,59 @@
+runtime ftplugin/man.vim
+
+function Test_g_ft_man_open_mode()
+  let l:w = winwidth(1)
+  vnew
+  let l:h = winheight(1)
+  q
+
+  " split horizontally
+  let wincnt = winnr('$')
+  Man 'vim'
+  if wincnt == winnr('$')
+    " Vim manual page cannot be found.
+    return
+  endif
+  call assert_equal(l:w, winwidth(1))
+  call assert_true(l:h > winheight(1))
+  call assert_equal(1, tabpagenr('$'))
+  call assert_equal(1, tabpagenr())
+  q
+
+  " split horizontally
+  let g:ft_man_open_mode = "horz"
+  Man 'vim'
+  call assert_equal(l:w, winwidth(1))
+  call assert_true(l:h > winheight(1))
+  call assert_equal(1, tabpagenr('$'))
+  call assert_equal(1, tabpagenr())
+  q
+
+  " split vertically
+  let g:ft_man_open_mode = "vert"
+  Man 'vim'
+  call assert_true(l:w > winwidth(1))
+  call assert_equal(l:h, winheight(1))
+  call assert_equal(1, tabpagenr('$'))
+  call assert_equal(1, tabpagenr())
+  q
+
+  " separate tab
+  let g:ft_man_open_mode = "tab"
+  Man 'vim'
+  call assert_equal(l:w, winwidth(1))
+  call assert_equal(l:h, winheight(1))
+  call assert_equal(2, tabpagenr('$'))
+  call assert_equal(2, tabpagenr())
+  q
+endfunction
+
+function Test_nomodifiable()
+  let wincnt = winnr('$')
+  Man 'vim'
+  if wincnt == winnr('$')
+    " Vim manual page cannot be found.
+    return
+  endif
+  call assert_false(&l:modifiable)
+  q
+endfunction