--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,9 @@
 2010-01-24  Bruno Haible  <bruno@clisp.org>
 
+	Tests for module 'logb'.
+	* modules/logb-tests: New file.
+	* tests/test-logb.c: New file.
+
 	Tests for module 'log1p'.
 	* modules/log1p-tests: New file.
 	* tests/test-log1p.c: New file.

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

new file mode 100644
--- /dev/null
+++ b/tests/test-logb.c
@@ -0,0 +1,62 @@
+/* Test of logb() 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 (logb, double, (double));
+
+#include <float.h>
+
+#include "macros.h"
+
+volatile double x;
+double y;
+
+int
+main ()
+{
+  /* Some particular values.  */
+  x = 0.6;
+  y = logb (x);
+  ASSERT (y == -1.0);
+
+  x = 1.2;
+  y = logb (x);
+  ASSERT (y == 0.0);
+
+  x = 2.1;
+  y = logb (x);
+  ASSERT (y == 1.0);
+
+  x = 3.9;
+  y = logb (x);
+  ASSERT (y == 1.0);
+
+  x = 4.0;
+  y = logb (x);
+  ASSERT (y == (FLT_RADIX == 2 ? 2.0 : 1.0));
+
+  x = 0.25;
+  y = logb (x);
+  ASSERT (y == (FLT_RADIX == 2 ? -2.0 : -1.0));
+
+  return 0;
+}