--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,9 @@
 2010-01-24  Bruno Haible  <bruno@clisp.org>
 
+	Tests for module 'modf'.
+	* modules/modf-tests: New file.
+	* tests/test-modf.c: New file.
+
 	Tests for module 'logb'.
 	* modules/logb-tests: New file.
 	* tests/test-logb.c: New file.

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

new file mode 100644
--- /dev/null
+++ b/tests/test-modf.c
@@ -0,0 +1,48 @@
+/* Test of modf() 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 <math.h>
+
+#include "signature.h"
+SIGNATURE_CHECK (modf, double, (double, double *));
+
+#include "macros.h"
+
+volatile double x;
+double y;
+double z;
+
+int
+main ()
+{
+  /* A particular positive value.  */
+  x = 5.972406760;
+  y = modf (x, &z);
+  ASSERT (y >= 0.972406759 && y <= 0.972406761);
+  ASSERT (z == 5.0);
+
+  /* A particular negative value.  */
+  x = -5.972406760;
+  y = modf (x, &z);
+  ASSERT (y >= -0.972406761 && y <= 0.972406759);
+  ASSERT (z == -5.0);
+
+  return 0;
+}