--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,9 @@
 2010-01-24  Bruno Haible  <bruno@clisp.org>
 
+	Tests for module 'yn'.
+	* modules/yn-tests: New file.
+	* tests/test-yn.c: New file.
+
 	Tests for module 'y1'.
 	* modules/y1-tests: New file.
 	* tests/test-y1.c: New file.

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

new file mode 100644
--- /dev/null
+++ b/tests/test-yn.c
@@ -0,0 +1,90 @@
+/* Test of yn() 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 (yn, double, (int, double));
+
+#include "macros.h"
+
+volatile double x;
+double y;
+
+int
+main ()
+{
+  /* A particular value.  */
+  x = 3.8;
+  y = yn (0, x);
+  ASSERT (y >= 0.0645032466 && y <= 0.0645032467);
+
+  /* A particular value.  */
+  x = 3.8;
+  y = yn (1, x);
+  ASSERT (y >= 0.4141146893 && y <= 0.4141146894);
+
+  /* A particular value.  */
+  x = 3.8;
+  y = yn (2, x);
+  ASSERT (y >= 0.1534518529 && y <= 0.1534518530);
+
+  /* A particular value.  */
+  x = 3.8;
+  y = yn (3, x);
+  ASSERT (y >= -0.2525864231 && y <= -0.2525864230);
+
+  /* A particular value.  */
+  x = 3.8;
+  y = yn (4, x);
+  ASSERT (y >= -0.5522725209 && y <= -0.5522725208);
+
+  /* A particular value.  */
+  x = 3.8;
+  y = yn (5, x);
+  ASSERT (y >= -0.9100925684 && y <= -0.9100925683);
+
+  /* A particular value.  */
+  x = 3.8;
+  y = yn (6, x);
+  ASSERT (y >= -1.842707923 && y <= -1.842707922);
+
+  /* A particular value.  */
+  x = 3.8;
+  y = yn (7, x);
+  ASSERT (y >= -4.908985081 && y <= -4.908985080);
+
+  /* A particular value.  */
+  x = 3.8;
+  y = yn (8, x);
+  ASSERT (y >= -16.24302659 && y <= -16.24302658);
+
+  /* A particular value.  */
+  x = 3.8;
+  y = yn (9, x);
+  ASSERT (y >= -63.48270581 && y <= -63.48270580);
+
+  /* A particular value.  */
+  x = 3.8;
+  y = yn (10, x);
+  ASSERT (y >= -284.4645273 && y <= -284.4645272);
+
+  return 0;
+}