new file mode 100644
--- /dev/null
+++ b/tests/test-fwritable.c
@@ -0,0 +1,115 @@
+/* Test of fwritable() function.
+   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 "fwritable.h"
+
+#include <stdlib.h>
+
+#define ASSERT(expr) if (!(expr)) abort ();
+
+#define TESTFILE "t-fwritable.tmp"
+
+int
+main ()
+{
+  FILE *fp;
+
+  /* Create a file with some contents.  */
+  fp = fopen (TESTFILE, "w");
+  if (fp == NULL)
+    goto skip;
+  ASSERT (fwritable (fp));
+  if (fwrite ("foobarsh", 1, 8, fp) < 8)
+    goto skip;
+  ASSERT (fwritable (fp));
+  if (fclose (fp))
+    goto skip;
+
+  /* Open it in read-only mode.  */
+  fp = fopen (TESTFILE, "r");
+  if (fp == NULL)
+    goto skip;
+  ASSERT (!fwritable (fp));
+  if (fgetc (fp) != 'f')
+    goto skip;
+  ASSERT (!fwritable (fp));
+  if (fseek (fp, 2, SEEK_CUR))
+    goto skip;
+  ASSERT (!fwritable (fp));
+  if (fgetc (fp) != 'b')
+    goto skip;
+  ASSERT (!fwritable (fp));
+  fflush (fp);
+  ASSERT (!fwritable (fp));
+  if (fgetc (fp) != 'a')
+    goto skip;
+  ASSERT (!fwritable (fp));
+  if (fseek (fp, 0, SEEK_END))
+    goto skip;
+  ASSERT (!fwritable (fp));
+  if (fclose (fp))
+    goto skip;
+
+  /* Open it in read-write mode.  */
+  fp = fopen (TESTFILE, "r+");
+  if (fp == NULL)
+    goto skip;
+  ASSERT (fwritable (fp));
+  if (fgetc (fp) != 'f')
+    goto skip;
+  ASSERT (fwritable (fp));
+  if (fseek (fp, 2, SEEK_CUR))
+    goto skip;
+  ASSERT (fwritable (fp));
+  if (fgetc (fp) != 'b')
+    goto skip;
+  ASSERT (fwritable (fp));
+  fflush (fp);
+  ASSERT (fwritable (fp));
+  if (fgetc (fp) != 'a')
+    goto skip;
+  ASSERT (fwritable (fp));
+  if (fputc ('z', fp) != 'z')
+    goto skip;
+  ASSERT (fwritable (fp));
+  if (fseek (fp, 0, SEEK_END))
+    goto skip;
+  ASSERT (fwritable (fp));
+  if (fclose (fp))
+    goto skip;
+
+  /* Open it in append mode.  */
+  fp = fopen (TESTFILE, "a");
+  if (fp == NULL)
+    goto skip;
+  ASSERT (fwritable (fp));
+  if (fwrite ("bla", 1, 3, fp) < 3)
+    goto skip;
+  ASSERT (fwritable (fp));
+  if (fclose (fp))
+    goto skip;
+
+  return 0;
+
+ skip:
+  fprintf (stderr, "Skipping test: file operations failed.\n");
+  return 77;
+}