--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,9 @@
 2010-01-10  Bruno Haible  <bruno@clisp.org>
 
+	Tests for module 'unistr/u16-next'.
+	* modules/unistr/u16-next-tests: New file.
+	* tests/unistr/test-u16-next.c: New file.
+
 	Tests for module 'unistr/u8-next'.
 	* modules/unistr/u8-next-tests: New file.
 	* tests/unistr/test-u8-next.c: New file.

new file mode 100644
--- /dev/null
+++ b/modules/unistr/u16-next-tests
@@ -0,0 +1,12 @@
+Files:
+tests/unistr/test-u16-next.c
+tests/macros.h
+
+Depends-on:
+
+configure.ac:
+
+Makefile.am:
+TESTS += test-u16-next
+check_PROGRAMS += test-u16-next
+test_u16_next_SOURCES = unistr/test-u16-next.c

new file mode 100644
--- /dev/null
+++ b/tests/unistr/test-u16-next.c
@@ -0,0 +1,91 @@
+/* Test of u16_next() function.
+   Copyright (C) 2010 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>, 2010.  */
+
+#include <config.h>
+
+#include "unistr.h"
+
+#include "macros.h"
+
+int
+main ()
+{
+  ucs4_t uc;
+  const uint16_t *ret;
+
+  /* Test NUL unit input.  */
+  {
+    static const uint16_t input[] = { 0 };
+    uc = 0xBADFACE;
+    ret = u16_next (&uc, input);
+    ASSERT (ret == NULL);
+    ASSERT (uc == 0);
+  }
+
+  /* Test ISO 646 unit input.  */
+  {
+    ucs4_t c;
+    uint16_t buf[2];
+
+    for (c = 1; c < 0x80; c++)
+      {
+        buf[0] = c;
+        buf[1] = 0;
+        uc = 0xBADFACE;
+        ret = u16_next (&uc, buf);
+        ASSERT (ret == buf + 1);
+        ASSERT (uc == c);
+      }
+  }
+
+  /* Test BMP unit input.  */
+  {
+    static const uint16_t input[] = { 0x20AC, 0 };
+    uc = 0xBADFACE;
+    ret = u16_next (&uc, input);
+    ASSERT (ret == input + 1);
+    ASSERT (uc == 0x20AC);
+  }
+
+  /* Test 2-units character input.  */
+  {
+    static const uint16_t input[] = { 0xD835, 0xDD1F, 0 };
+    uc = 0xBADFACE;
+    ret = u16_next (&uc, input);
+    ASSERT (ret == input + 2);
+    ASSERT (uc == 0x1D51F);
+  }
+
+  /* Test incomplete/invalid 1-unit input.  */
+  {
+    static const uint16_t input[] = { 0xD835, 0 };
+    uc = 0xBADFACE;
+    ret = u16_next (&uc, input);
+    ASSERT (ret == NULL);
+    ASSERT (uc == 0xFFFD);
+  }
+  {
+    static const uint16_t input[] = { 0xDD1F, 0 };
+    uc = 0xBADFACE;
+    ret = u16_next (&uc, input);
+    ASSERT (ret == NULL);
+    ASSERT (uc == 0xFFFD);
+  }
+
+  return 0;
+}