--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,9 @@
 2011-10-09  Bruno Haible  <bruno@clisp.org>
 
+	Tests for module 'copysignl'.
+	* modules/copysignl-tests: New file.
+	* tests/test-copysignl.c: New file.
+
 	New module 'copysignl'.
 	* lib/math.in.h (copysignl): New declaration.
 	* lib/copysignl.c: New file.

new file mode 100644
--- /dev/null
+++ b/modules/copysignl-tests
@@ -0,0 +1,14 @@
+Files:
+tests/test-copysignl.c
+tests/signature.h
+tests/minus-zero.h
+tests/macros.h
+
+Depends-on:
+
+configure.ac:
+
+Makefile.am:
+TESTS += test-copysignl
+check_PROGRAMS += test-copysignl
+test_copysignl_LDADD = $(LDADD) @COPYSIGNL_LIBM@

new file mode 100644
--- /dev/null
+++ b/tests/test-copysignl.c
@@ -0,0 +1,111 @@
+/* Test of copysignl() 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 (copysignl, long double, (long double, long double));
+
+#include "macros.h"
+#include "minus-zero.h"
+
+#include <string.h>
+
+volatile long double x;
+volatile long double y;
+long double z;
+long double zero = 0.0L;
+
+int
+main ()
+{
+  /* A particular value in the first quadrant.  */
+  x = 0.6L;
+  y = 0.8L;
+  z = copysignl (x, y);
+  ASSERT (z == 0.6L);
+
+  /* A particular value in the second quadrant.  */
+  x = -0.6L;
+  y = 0.8L;
+  z = copysignl (x, y);
+  ASSERT (z == 0.6L);
+
+  /* A particular value in the third quadrant.  */
+  x = -0.6L;
+  y = -0.8L;
+  z = copysignl (x, y);
+  ASSERT (z == -0.6L);
+
+  /* A particular value in the fourth quadrant.  */
+  x = 0.6L;
+  y = -0.8L;
+  z = copysignl (x, y);
+  ASSERT (z == -0.6L);
+
+  /* From signed zero.  */
+  x = 1.0L;
+  y = 0.0L;
+  z = copysignl (x, y);
+  ASSERT (z == 1.0L);
+
+  x = 1.0L;
+  y = minus_zerol;
+  z = copysignl (x, y);
+  /* Assume all gnulib targets support -0.0L, until proven otherwise.  */
+  ASSERT (z == -1.0L);
+
+  x = -1.0L;
+  y = 0.0L;
+  z = copysignl (x, y);
+  ASSERT (z == 1.0L);
+
+  x = -1.0L;
+  y = minus_zerol;
+  z = copysignl (x, y);
+  ASSERT (z == -1.0L);
+
+  /* To signed zero.  */
+  x = 0.0L;
+  y = 1.0L;
+  z = copysignl (x, y);
+  ASSERT (z == 0.0L);
+  ASSERT (memcmp (&z, &zero, sizeof z) == 0);
+
+  x = 0.0L;
+  y = -1.0L;
+  z = copysignl (x, y);
+  ASSERT (z == 0.0L);
+  ASSERT (memcmp (&z, &zero, sizeof z) != 0);
+
+  x = minus_zerol;
+  y = 1.0L;
+  z = copysignl (x, y);
+  ASSERT (z == 0.0L);
+  ASSERT (memcmp (&z, &zero, sizeof z) == 0);
+
+  x = minus_zerol;
+  y = -1.0L;
+  z = copysignl (x, y);
+  ASSERT (z == 0.0L);
+  ASSERT (memcmp (&z, &zero, sizeof z) != 0);
+
+  return 0;
+}