--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,9 @@
 2011-10-14  Bruno Haible  <bruno@clisp.org>
 
+	Tests for module 'integer_length_l'.
+	* modules/integer_length_l-tests: New file.
+	* tests/test-integer_length_l.c: New file.
+
 	New module 'integer_length_l'.
 	* lib/integer_length_l.c: New file.
 	* modules/integer_length_l: New file.

new file mode 100644
--- /dev/null
+++ b/modules/integer_length_l-tests
@@ -0,0 +1,11 @@
+Files:
+tests/test-integer_length_l.c
+tests/macros.h
+
+Depends-on:
+
+configure.ac:
+
+Makefile.am:
+TESTS += test-integer_length_l
+check_PROGRAMS += test-integer_length_l

new file mode 100644
--- /dev/null
+++ b/tests/test-integer_length_l.c
@@ -0,0 +1,66 @@
+/* Test of integer_length_l().
+   Copyright (C) 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/>.  */
+
+#include <config.h>
+
+#include "integer_length.h"
+
+#include <limits.h>
+
+#include "macros.h"
+
+#define NBITS (sizeof (unsigned long) * CHAR_BIT)
+
+static int
+naive (unsigned long x)
+{
+  int j;
+  for (j = NBITS - 1; j >= 0; j--)
+    if (x & (1UL << j))
+      return j + 1;
+  return 0;
+}
+
+int
+main (int argc, char *argv[])
+{
+  unsigned long x;
+  int i;
+
+  for (x = 0; x <= 256; x++)
+    ASSERT (integer_length_l (x) == naive (x));
+  for (i = 0; i < NBITS; i++)
+    {
+      ASSERT (integer_length_l (1UL << i) == naive (1UL << i));
+      ASSERT (integer_length_l (1UL << i) == i + 1);
+      ASSERT (integer_length_l (-1UL << i) == NBITS);
+    }
+  for (i = 0; i < NBITS - 1; i++)
+    ASSERT (integer_length_l (3UL << i) == i + 2);
+  for (i = 0; i < NBITS - 2; i++)
+    ASSERT (integer_length_l (-3UL << i) == NBITS);
+  for (i = 0; i < NBITS - 2; i++)
+    {
+      ASSERT (integer_length_l (5UL << i) == i + 3);
+      ASSERT (integer_length_l (7UL << i) == i + 3);
+    }
+  for (i = 0; i < NBITS - 3; i++)
+    {
+      ASSERT (integer_length_l (-5UL << i) == NBITS);
+      ASSERT (integer_length_l (-7UL << i) == NBITS);
+    }
+  return 0;
+}