--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,9 @@
 2011-10-05  Bruno Haible  <bruno@clisp.org>
 
+	Tests for module 'modff'.
+	* modules/modff-tests: New file.
+	* tests/test-modff.c: New file.
+
 	New module 'modff'.
 	* lib/math.in.h (modff): New declaration.
 	* lib/modff.c: New file.

new file mode 100644
--- /dev/null
+++ b/modules/modff-tests
@@ -0,0 +1,13 @@
+Files:
+tests/test-modff.c
+tests/signature.h
+tests/macros.h
+
+Depends-on:
+
+configure.ac:
+
+Makefile.am:
+TESTS += test-modff
+check_PROGRAMS += test-modff
+test_modff_LDADD = $(LDADD) @MODFF_LIBM@

new file mode 100644
--- /dev/null
+++ b/tests/test-modff.c
@@ -0,0 +1,48 @@
+/* Test of modff() function.
+   Copyright (C) 2010-2011 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>, 2010-2011.  */
+
+#include <config.h>
+
+#include <math.h>
+
+#include "signature.h"
+SIGNATURE_CHECK (modff, float, (float, float *));
+
+#include "macros.h"
+
+volatile float x;
+float y;
+float z;
+
+int
+main ()
+{
+  /* A particular positive value.  */
+  x = 5.972407f;
+  y = modff (x, &z);
+  ASSERT (y >= 0.972406f && y <= 0.972408f);
+  ASSERT (z == 5.0f);
+
+  /* A particular negative value.  */
+  x = -5.972407f;
+  y = modff (x, &z);
+  ASSERT (y >= -0.972408f && y <= -0.972406f);
+  ASSERT (z == -5.0f);
+
+  return 0;
+}