--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,9 @@
 2009-11-22  Bruno Haible  <bruno@clisp.org>
 
+	Tests for module 'duplocale'.
+	* modules/duplocale-tests: New file.
+	* tests/test-duplocale.c: New file.
+
 	New module 'duplocale'.
 	* m4/duplocale.m4: New file.
 	* lib/locale.in.h (duplocale): New declaration.

new file mode 100644
--- /dev/null
+++ b/modules/duplocale-tests
@@ -0,0 +1,11 @@
+Files:
+tests/test-duplocale.c
+
+Depends-on:
+
+configure.ac:
+AC_CHECK_FUNCS_ONCE([duplocale])
+
+Makefile.am:
+TESTS += test-duplocale
+check_PROGRAMS += test-duplocale

new file mode 100644
--- /dev/null
+++ b/tests/test-duplocale.c
@@ -0,0 +1,107 @@
+/* Test of duplicating a locale object.
+   Copyright (C) 2009 Free Software Foundation, Inc.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+/* Written by Bruno Haible <bruno@clisp.org>, 2007.  */
+
+#include <config.h>
+
+#include <locale.h>
+
+#if HAVE_DUPLOCALE
+
+#include <langinfo.h>
+#include <monetary.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define ASSERT(expr) \
+  do									     \
+    {									     \
+      if (!(expr))							     \
+        {								     \
+          fprintf (stderr, "%s:%d: assertion failed\n", __FILE__, __LINE__); \
+          fflush (stderr);						     \
+          abort ();							     \
+        }								     \
+    }									     \
+  while (0)
+
+struct locale_dependent_values
+{
+  char monetary[100];
+  char numeric[100];
+  char time[100];
+};
+
+static void
+get_locale_dependent_values (struct locale_dependent_values *result)
+{
+  strfmon (result->monetary, sizeof (result->monetary),
+	   "%n", 123.75);
+  /* result->monetary is usually "$123.75" */
+  snprintf (result->numeric, sizeof (result->numeric),
+	    "%g", 3.5);
+  /* result->numeric is usually "3,5" */
+  strcpy (result->time, nl_langinfo (MON_1));
+  /* result->time is usually "janvier" */
+}
+
+int
+main ()
+{
+  struct locale_dependent_values expected_results;
+  locale_t mixed;
+
+  /* Set up a locale which is a mix between different system locales.  */
+  setlocale (LC_ALL, "en_US.UTF-8");
+  setlocale (LC_NUMERIC, "de_DE.UTF-8");
+  setlocale (LC_TIME, "fr_FR.UTF-8");
+  get_locale_dependent_values (&expected_results);
+
+  /* Save the locale in a locale_t object.  */
+  mixed = duplocale (LC_GLOBAL_LOCALE);
+  ASSERT (mixed != NULL);
+
+  /* Set up a default locale.  */
+  setlocale (LC_ALL, "C");
+  {
+    struct locale_dependent_values c_results;
+    get_locale_dependent_values (&c_results);
+  }
+
+  /* Now use the saved locale again.  */
+  uselocale (mixed);
+  {
+    struct locale_dependent_values results;
+    get_locale_dependent_values (&results);
+    ASSERT (strcmp (results.monetary, expected_results.monetary) == 0);
+    ASSERT (strcmp (results.numeric, expected_results.numeric) == 0);
+    ASSERT (strcmp (results.time, expected_results.time) == 0);
+  }
+
+  return 0;
+}
+
+#else
+
+int
+main ()
+{
+  return 77;
+}
+
+#endif