new file mode 100644
--- /dev/null
+++ b/modules/pwrite-tests
@@ -0,0 +1,14 @@
+Files:
+tests/test-pwrite.sh
+tests/test-pwrite.c
+tests/init.sh
+tests/signature.h
+tests/macros.h
+
+Depends-on:
+
+configure.ac:
+
+Makefile.am:
+TESTS += test-pwrite.sh
+check_PROGRAMS += test-pwrite

new file mode 100644
--- /dev/null
+++ b/tests/test-pwrite.c
@@ -0,0 +1,80 @@
+/* Test the pwrite function.
+   Copyright (C) 2009, 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/>.  */
+
+#include <config.h>
+
+#include <unistd.h>
+
+#include "signature.h"
+SIGNATURE_CHECK (pwrite, ssize_t, (int, const void *, size_t, off_t));
+
+#include <sys/types.h>
+#include <fcntl.h>
+#include <errno.h>
+
+#include "macros.h"
+
+#define N (sizeof buf - 1)
+
+int
+main (void)
+{
+  char const *file = "out";
+  int fd;
+  char buf[] = "0123456789";
+  off_t pos = 2;
+  size_t i;
+  off_t init_pos;
+
+  ASSERT (file);
+
+  fd = open (file, O_CREAT | O_WRONLY, 0600);
+  ASSERT (0 <= fd);
+  ASSERT (write (fd, buf, N) == N);
+  ASSERT (close (fd) == 0);
+
+  fd = open (file, O_WRONLY, 0600);
+  ASSERT (0 <= fd);
+
+  init_pos = lseek (fd, pos, SEEK_SET);
+  ASSERT (init_pos == pos);
+
+  for (i = 0; i < N; i+=2)
+    {
+      const char byte = 'W';
+      ASSERT (pwrite (fd, &byte, 1, i) == 1);
+      ASSERT (lseek (fd, 0, SEEK_CUR) == init_pos);
+    }
+
+  {
+    /* Invalid offset must evoke failure with EINVAL.  */
+    const char byte = 'b';
+    ASSERT (pwrite (fd, &byte, 1, (off_t) -1) == -1);
+    ASSERT (errno == EINVAL);
+  }
+
+  ASSERT (close (fd) == 0);
+
+  {
+    char read_buf[N];
+    fd = open (file, O_RDONLY);
+    ASSERT (0 <= fd);
+    ASSERT (read (fd, buf, N) == N);
+    ASSERT (close (fd) == 0);
+    ASSERT (strcmp ("W1W3W5W7W9",buf) == 0);
+  }
+  return 0;
+}

new file mode 100644
--- /dev/null
+++ b/tests/test-pwrite.sh
@@ -0,0 +1,7 @@
+#!/bin/sh
+. "${srcdir=.}/init.sh"; path_prepend_ .
+
+fail=0
+test-pwrite || fail=1
+
+Exit $fail