diff --git a/libcxx/test/support/make_string.h b/libcxx/test/support/make_string.h
new file mode 100644
--- /dev/null
+++ b/libcxx/test/support/make_string.h
@@ -0,0 +1,57 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef SUPPORT_TEST_MAKE_STRING_H
+#define SUPPORT_TEST_MAKE_STRING_H
+
+#include "test_macros.h"
+
+#if TEST_STD_VER < 11
+#error This header requires C++11 or greater
+#endif
+
+#include <string>
+#include <locale>
+#include <codecvt>
+
+// Some of these std::codecvt specializations have been deprecated. At the
+// moment are no replacements in the Standard so use the deprecated facilities.
+_LIBCPP_SUPPRESS_DEPRECATED_PUSH
+// Helper function to convert a const char* string to a basic_string<CharT>.
+// This helper is used in unit tests to make them generic. The input should be
+// valid ASCII which means the input is also valid UTF-8.
+template <class CharT>
+std::basic_string<CharT> make_string(const char* str) {
+  struct convertor_type : public std::codecvt<CharT, char, std::mbstate_t> {
+    using std::codecvt<CharT, char, std::mbstate_t>::codecvt;
+    ~convertor_type() = default;
+  };
+
+  std::wstring_convert<convertor_type, CharT> convertor;
+  return convertor.from_bytes(str);
+}
+_LIBCPP_SUPPRESS_DEPRECATED_POP
+
+template <>
+std::basic_string<char> make_string(const char* str) {
+  return std::basic_string<char>(str);
+}
+
+#ifndef _LIBCPP_NO_HAS_CHAR8_T
+template <>
+std::basic_string<char8_t> make_string(const char* str) {
+  std::basic_string<char8_t> result;
+  auto out = std::back_inserter(result);
+  while (*str)
+    out = *str++;
+
+  return result;
+}
+#endif
+
+#endif
diff --git a/libcxx/test/support/test.support/make_string_header.pass.cpp b/libcxx/test/support/test.support/make_string_header.pass.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/support/test.support/make_string_header.pass.cpp
@@ -0,0 +1,52 @@
+//===----------------------------------------------------------------------===//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03
+// UNSUPPORTED: libcpp-has-no-localization
+
+// "support/make_string.h"
+
+#include "make_string.h"
+#include <cassert>
+
+#include "test_macros.h"
+
+int main(int, char**) {
+  assert(
+      make_string<char>(" !\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMN"
+                        "OPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~") ==
+      " !\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMN"
+      "OPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~");
+
+  assert(make_string<wchar_t>(
+             " !\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMN"
+             "OPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~") ==
+         L" !\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMN"
+         "OPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~");
+#ifndef _LIBCPP_NO_HAS_CHAR8_T
+  assert(make_string<char8_t>(
+             " !\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMN"
+             "OPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~") ==
+         u8" !\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMN"
+         "OPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~");
+#endif
+#ifndef _LIBCPP_HAS_NO_UNICODE_CHARS
+  assert(make_string<char16_t>(
+             " !\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMN"
+             "OPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~") ==
+         u" !\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMN"
+         "OPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~");
+
+  assert(make_string<char32_t>(
+             " !\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMN"
+             "OPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~") ==
+         U" !\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMN"
+         "OPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~");
+#endif
+
+  return 0;
+}