--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,8 @@
 2007-02-24  Bruno Haible  <bruno@clisp.org>
 
+	* modules/isnan-nolibm-tests: New file.
+	* tests/test-isnan.c: New file.
+
 	* modules/isnan-nolibm: New file.
 	* lib/isnan.h: New file.
 	* lib/isnan.c: New file.

new file mode 100644
--- /dev/null
+++ b/modules/isnan-nolibm-tests
@@ -0,0 +1,12 @@
+Files:
+tests/test-isnan.c
+
+Depends-on:
+
+configure.ac:
+gl_DOUBLE_EXPONENT_LOCATION
+
+Makefile.am:
+TESTS += test-isnan
+check_PROGRAMS += test-isnan
+

new file mode 100644
--- /dev/null
+++ b/tests/test-isnan.c
@@ -0,0 +1,64 @@
+/* Test of isnan() substitute.
+   Copyright (C) 2007 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 2, 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, write to the Free Software Foundation,
+   Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
+
+/* Written by Bruno Haible <bruno@clisp.org>, 2007.  */
+
+#include <config.h>
+
+#include "isnan.h"
+
+#include <limits.h>
+#include <stdlib.h>
+
+#define ASSERT(expr) if (!(expr)) abort ();
+
+int
+main ()
+{
+  /* Finite values.  */
+  ASSERT (!isnan (3.141));
+  ASSERT (!isnan (3.141e30));
+  ASSERT (!isnan (3.141e-30));
+  ASSERT (!isnan (-2.718));
+  ASSERT (!isnan (-2.718e30));
+  ASSERT (!isnan (-2.718e-30));
+  /* Infinite values.  */
+  ASSERT (!isnan (1.0 / 0.0));
+  ASSERT (!isnan (-1.0 / 0.0));
+  /* Quiet NaN.  */
+  ASSERT (isnan (0.0 / 0.0));
+#if defined DBL_EXPBIT0_WORD && defined DBL_EXPBIT0_BIT
+  /* Signalling NaN.  */
+  {
+    #define NWORDS \
+      ((sizeof (double) + sizeof (unsigned int) - 1) / sizeof (unsigned int))
+    typedef union { double value; unsigned int word[NWORDS]; } memory_double;
+    memory_double m;
+    m.value = 0.0 / 0.0;
+# if DBL_EXPBIT0_BIT > 0
+    m.word[DBL_EXPBIT0_WORD] ^= (unsigned int) 1 << (DBL_EXPBIT0_BIT - 1);
+# else
+    m.word[DBL_EXPBIT0_WORD + (DBL_EXPBIT0_WORD < NWORDS / 2 ? 1 : - 1)]
+      ^= (unsigned int) 1 << (sizeof (unsigned int) * CHAR_BIT - 1);
+# endif
+    m.word[DBL_EXPBIT0_WORD + (DBL_EXPBIT0_WORD < NWORDS / 2 ? 1 : - 1)]
+      |= (unsigned int) 1 << DBL_EXPBIT0_BIT;
+    ASSERT (isnan (m.value));
+  }
+#endif
+  return 0;
+}