diff --git a/string/Makefile b/string/Makefile
index 472e318aea..2eef6f1dfc 100644
--- a/string/Makefile
+++ b/string/Makefile
@@ -163,6 +163,7 @@ tests := \
   test-strncat \
   test-strncmp \
   test-strncpy \
+  test-strndup \
   test-strnlen \
   test-strpbrk \
   test-strrchr \
diff --git a/string/test-strndup.c b/string/test-strndup.c
new file mode 100644
index 0000000000..032b0775b8
--- /dev/null
+++ b/string/test-strndup.c
@@ -0,0 +1,266 @@
+/* Test strndup functions.
+   Copyright (C) 2023 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library 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
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#ifdef WIDE
+# include <wchar.h>
+# define CHAR wchar_t
+# define UCHAR wchar_t
+# define BIG_CHAR WCHAR_MAX
+# define SMALL_CHAR 1273
+# define MEMCMP wmemcmp
+# define MEMSET wmemset
+# define STRNLEN wcsnlen
+#else
+# define CHAR char
+# define UCHAR unsigned char
+# define BIG_CHAR CHAR_MAX
+# define SMALL_CHAR 127
+# define MEMCMP memcmp
+# define MEMSET memset
+# define STRNLEN strnlen
+#endif /* !WIDE */
+
+
+#ifndef STRNDUP_RESULT
+# define STRNDUP_RESULT(dst, len, n) dst
+# define TEST_MAIN
+# ifndef WIDE
+#  define TEST_NAME "strndup"
+# else
+#  define TEST_NAME "wcsndup"
+# endif /* WIDE */
+# include "test-string.h"
+# ifndef WIDE
+#  define STRNDUP strndup
+# else
+#  define STRNDUP wcsndup
+# endif /* WIDE */
+
+
+IMPL (STRNDUP, 1)
+
+
+#endif /* !STRNDUP_RESULT */
+
+typedef CHAR *(*proto_t) (const CHAR *, size_t);
+
+static void
+do_one_test (impl_t *impl, const CHAR *src, size_t len, size_t n)
+{
+  char *dst;
+  dst = CALL (impl, src, n);
+  size_t res;
+
+  res = memcmp (dst, src, (len > n ? n : len) * sizeof (CHAR));
+  if (res != 0)
+    {
+      printf("JOE: res: %ld\n", res);
+      error (0, 0, "Wrong result in function %s", impl->name);
+      ret = 1;
+      return;
+    }
+}
+
+static void
+do_test (size_t align1, size_t align2, size_t len, size_t n, int max_char)
+{
+  size_t i;
+  CHAR *s1;
+
+/* For wcsndup: align1 and align2 here mean alignment not in bytes,
+   but in wchar_ts, in bytes it will equal to align * (sizeof (wchar_t)).  */
+  align1 &= 7;
+  if ((align1 + len) * sizeof (CHAR) >= page_size)
+    return;
+
+  align2 &= 7;
+  if ((align2 + len) * sizeof (CHAR) >= page_size)
+    return;
+
+  s1 = (CHAR *) (buf1) + align1;
+
+  for (i = 0; i < len; ++i)
+    s1[i] = 32 + 23 * i % (max_char - 32);
+  s1[len] = 0;
+  for (i = len + 1; (i + align1) * sizeof (CHAR) < page_size && i < len + 64;
+       ++i)
+    s1[i] = 32 + 32 * i % (max_char - 32);
+
+  FOR_EACH_IMPL (impl, 0)
+    do_one_test (impl, s1, len, n);
+}
+
+static void
+do_page_tests (void)
+{
+  CHAR *s1;
+  const size_t maxoffset = 64;
+
+  /* Put s1 at the maxoffset from the edge of buf1's last page.  */
+  s1 = (CHAR *) buf1 + BUF1PAGES * page_size / sizeof(CHAR) - maxoffset;
+  /* s2 needs room to put a string with size of maxoffset + 1 at s2 +
+     (maxoffset - 1).  */
+
+  MEMSET (s1, 'a', maxoffset - 1);
+  s1[maxoffset - 1] = '\0';
+
+  /* Both strings are bounded to a page with read/write access and the next
+     page is protected with PROT_NONE (meaning that any access outside of the
+     page regions will trigger an invalid memory access).
+
+     The loop copies the string s1 for all possible offsets up to maxoffset
+     for both inputs with a size larger than s1 (so memory access outside the
+     expected memory regions might trigger invalid access).  */
+
+  for (size_t off1 = 0; off1 < maxoffset; off1++)
+    {
+      for (size_t off2 = 0; off2 < maxoffset; off2++)
+	{
+	  FOR_EACH_IMPL (impl, 0)
+	    do_one_test (impl, s1 + off1, maxoffset - off1 - 1,
+			 maxoffset + (maxoffset - off2));
+	}
+    }
+}
+
+static void
+do_random_tests (void)
+{
+  size_t i, j, n, align1, align2, len, size, mode;
+  UCHAR *p1 = (UCHAR *) (buf1 + page_size) - 512;
+  UCHAR *res;
+
+  for (n = 0; n < ITERATIONS; n++)
+    {
+      /* For wcsndup: align1 and align2 here mean align not in bytes,
+	 but in wchar_ts, in bytes it will equal to align * (sizeof
+	 (wchar_t)).  */
+
+      mode = random ();
+      if (mode & 1)
+	{
+	  size = random () & 255;
+	  align1 = 512 - size - (random () & 15);
+	  if (mode & 2)
+	    align2 = align1 - (random () & 24);
+	  else
+	    align2 = align1 - (random () & 31);
+	  if (mode & 4)
+	    {
+	      j = align1;
+	      align1 = align2;
+	      align2 = j;
+	    }
+	  if (mode & 8)
+	    len = size - (random () & 31);
+	  else
+	    len = 512;
+	  if (len >= 512)
+	    len = random () & 511;
+	}
+      else
+	{
+	  align1 = random () & 31;
+	  if (mode & 2)
+	    align2 = random () & 31;
+	  else
+	    align2 = align1 + (random () & 24);
+	  len = random () & 511;
+	  j = align1;
+	  if (align2 > j)
+	    j = align2;
+	  if (mode & 4)
+	    {
+	      size = random () & 511;
+	      if (size + j > 512)
+		size = 512 - j - (random () & 31);
+	    }
+	  else
+	    size = 512 - j;
+	  if ((mode & 8) && len + j >= 512)
+	    len = 512 - j - (random () & 7);
+	}
+      j = len + align1 + 64;
+      if (j > 512)
+	j = 512;
+      for (i = 0; i < j; i++)
+	{
+	  if (i == len + align1)
+	    p1[i] = 0;
+	  else
+	    {
+	      p1[i] = random () & BIG_CHAR;
+	      if (i >= align1 && i < len + align1 && !p1[i])
+		p1[i] = (random () & SMALL_CHAR) + 3;
+	    }
+	}
+
+      FOR_EACH_IMPL (impl, 1)
+	{
+	  res = (UCHAR *) CALL (impl, (CHAR *) (p1 + align1), size);
+	  j = len + 1;
+	  if (size < j)
+	    j = size;
+	  if (MEMCMP (p1 + align1, res, j))
+	    {
+	      error (0, 0, "Iteration %zd - different strings, %s (%zd, %zd, %zd)",
+		     n, impl->name, align1, align2, len);
+	      ret = 1;
+	    }
+	}
+    }
+}
+
+int
+test_main (void)
+{
+  size_t i;
+
+  test_init ();
+
+  printf ("%28s", "");
+  FOR_EACH_IMPL (impl, 0)
+    printf ("\t%s", impl->name);
+  putchar ('\n');
+
+  for (i = 1; i < 8; ++i)
+    {
+      do_test (i, i, 16, 16, SMALL_CHAR);
+      do_test (i, i, 16, 16, BIG_CHAR);
+      do_test (i, 2 * i, 16, 16, SMALL_CHAR);
+      do_test (2 * i, i, 16, 16, BIG_CHAR);
+      do_test (8 - i, 2 * i, 1 << i, 2 << i, SMALL_CHAR);
+      do_test (2 * i, 8 - i, 2 << i, 1 << i, SMALL_CHAR);
+      do_test (8 - i, 2 * i, 1 << i, 2 << i, BIG_CHAR);
+      do_test (2 * i, 8 - i, 2 << i, 1 << i, BIG_CHAR);
+    }
+
+  for (i = 1; i < 8; ++i)
+    {
+      do_test (0, 0, 4 << i, 8 << i, SMALL_CHAR);
+      do_test (0, 0, 16 << i, 8 << i, SMALL_CHAR);
+      do_test (8 - i, 2 * i, 4 << i, 8 << i, SMALL_CHAR);
+      do_test (8 - i, 2 * i, 16 << i, 8 << i, SMALL_CHAR);
+    }
+
+  do_random_tests ();
+  do_page_tests ();
+  return ret;
+}
+
+#include <support/test-driver.c>
