diff --git a/libcxx/test/std/language.support/cmp/cmp.concept/three_way_comparable.compile.pass.cpp b/libcxx/test/std/language.support/cmp/cmp.concept/three_way_comparable.compile.pass.cpp
index 1fd2a171d807a..b65b77e96ef60 100644
--- a/libcxx/test/std/language.support/cmp/cmp.concept/three_way_comparable.compile.pass.cpp
+++ b/libcxx/test/std/language.support/cmp/cmp.concept/three_way_comparable.compile.pass.cpp
@@ -27,7 +27,7 @@ static_assert(std::three_way_comparable<char const*>);
 static_assert(std::three_way_comparable<char volatile*>);
 static_assert(std::three_way_comparable<char const volatile*>);
 static_assert(std::three_way_comparable<wchar_t&>);
-#ifndef _LIBCPP_HAS_NO_CHAR8_T
+#ifndef TEST_HAS_NO_CHAR8_T
 static_assert(std::three_way_comparable<char8_t const&>);
 #endif
 #ifndef TEST_HAS_NO_UNICODE_CHARS
diff --git a/libcxx/test/std/numerics/bit/bit.pow.two/bit_ceil.pass.cpp b/libcxx/test/std/numerics/bit/bit.pow.two/bit_ceil.pass.cpp
index e1dd88e85bf35..f18d52a0ed574 100644
--- a/libcxx/test/std/numerics/bit/bit.pow.two/bit_ceil.pass.cpp
+++ b/libcxx/test/std/numerics/bit/bit.pow.two/bit_ceil.pass.cpp
@@ -95,7 +95,7 @@ int main(int, char**)
     static_assert(!std::is_invocable_v<L, bool>);
     static_assert(!std::is_invocable_v<L, char>);
     static_assert(!std::is_invocable_v<L, wchar_t>);
-#ifndef _LIBCPP_HAS_NO_CHAR8_T
+#ifndef TEST_HAS_NO_CHAR8_T
     static_assert(!std::is_invocable_v<L, char8_t>);
 #endif
     static_assert(!std::is_invocable_v<L, char16_t>);
diff --git a/libcxx/test/std/numerics/bit/bit.pow.two/bit_floor.pass.cpp b/libcxx/test/std/numerics/bit/bit.pow.two/bit_floor.pass.cpp
index 045b1cc9a7ada..f89029017fa8d 100644
--- a/libcxx/test/std/numerics/bit/bit.pow.two/bit_floor.pass.cpp
+++ b/libcxx/test/std/numerics/bit/bit.pow.two/bit_floor.pass.cpp
@@ -91,7 +91,7 @@ int main(int, char**)
     static_assert(!std::is_invocable_v<L, bool>);
     static_assert(!std::is_invocable_v<L, char>);
     static_assert(!std::is_invocable_v<L, wchar_t>);
-#ifndef _LIBCPP_HAS_NO_CHAR8_T
+#ifndef TEST_HAS_NO_CHAR8_T
     static_assert(!std::is_invocable_v<L, char8_t>);
 #endif
     static_assert(!std::is_invocable_v<L, char16_t>);
diff --git a/libcxx/test/std/numerics/bit/bit.pow.two/bit_width.pass.cpp b/libcxx/test/std/numerics/bit/bit.pow.two/bit_width.pass.cpp
index 43f47d36bfe90..84b00efa7ed49 100644
--- a/libcxx/test/std/numerics/bit/bit.pow.two/bit_width.pass.cpp
+++ b/libcxx/test/std/numerics/bit/bit.pow.two/bit_width.pass.cpp
@@ -96,7 +96,7 @@ int main(int, char**)
     static_assert(!std::is_invocable_v<L, bool>);
     static_assert(!std::is_invocable_v<L, char>);
     static_assert(!std::is_invocable_v<L, wchar_t>);
-#ifndef _LIBCPP_HAS_NO_CHAR8_T
+#ifndef TEST_HAS_NO_CHAR8_T
     static_assert(!std::is_invocable_v<L, char8_t>);
 #endif
     static_assert(!std::is_invocable_v<L, char16_t>);
diff --git a/libcxx/test/std/numerics/bit/bit.pow.two/has_single_bit.pass.cpp b/libcxx/test/std/numerics/bit/bit.pow.two/has_single_bit.pass.cpp
index 687f9ad45ff1a..35343c5542404 100644
--- a/libcxx/test/std/numerics/bit/bit.pow.two/has_single_bit.pass.cpp
+++ b/libcxx/test/std/numerics/bit/bit.pow.two/has_single_bit.pass.cpp
@@ -94,7 +94,7 @@ int main(int, char**)
     static_assert(!std::is_invocable_v<L, bool>);
     static_assert(!std::is_invocable_v<L, char>);
     static_assert(!std::is_invocable_v<L, wchar_t>);
-#ifndef _LIBCPP_HAS_NO_CHAR8_T
+#ifndef TEST_HAS_NO_CHAR8_T
     static_assert(!std::is_invocable_v<L, char8_t>);
 #endif
     static_assert(!std::is_invocable_v<L, char16_t>);
diff --git a/libcxx/test/std/numerics/bit/bitops.count/countl_one.pass.cpp b/libcxx/test/std/numerics/bit/bitops.count/countl_one.pass.cpp
index 23196aa6ecf3d..9ee60a210d828 100644
--- a/libcxx/test/std/numerics/bit/bitops.count/countl_one.pass.cpp
+++ b/libcxx/test/std/numerics/bit/bitops.count/countl_one.pass.cpp
@@ -91,7 +91,7 @@ int main(int, char**)
     static_assert(!std::is_invocable_v<L, bool>);
     static_assert(!std::is_invocable_v<L, char>);
     static_assert(!std::is_invocable_v<L, wchar_t>);
-#ifndef _LIBCPP_HAS_NO_CHAR8_T
+#ifndef TEST_HAS_NO_CHAR8_T
     static_assert(!std::is_invocable_v<L, char8_t>);
 #endif
     static_assert(!std::is_invocable_v<L, char16_t>);
diff --git a/libcxx/test/std/numerics/bit/bitops.count/countl_zero.pass.cpp b/libcxx/test/std/numerics/bit/bitops.count/countl_zero.pass.cpp
index 51675808f8340..87d5cf2b7be5d 100644
--- a/libcxx/test/std/numerics/bit/bitops.count/countl_zero.pass.cpp
+++ b/libcxx/test/std/numerics/bit/bitops.count/countl_zero.pass.cpp
@@ -90,7 +90,7 @@ int main(int, char**)
     static_assert(!std::is_invocable_v<L, bool>);
     static_assert(!std::is_invocable_v<L, char>);
     static_assert(!std::is_invocable_v<L, wchar_t>);
-#ifndef _LIBCPP_HAS_NO_CHAR8_T
+#ifndef TEST_HAS_NO_CHAR8_T
     static_assert(!std::is_invocable_v<L, char8_t>);
 #endif
     static_assert(!std::is_invocable_v<L, char16_t>);
diff --git a/libcxx/test/std/numerics/bit/bitops.count/countr_one.pass.cpp b/libcxx/test/std/numerics/bit/bitops.count/countr_one.pass.cpp
index 448fdcbf12fe8..e57125e7e701f 100644
--- a/libcxx/test/std/numerics/bit/bitops.count/countr_one.pass.cpp
+++ b/libcxx/test/std/numerics/bit/bitops.count/countr_one.pass.cpp
@@ -95,7 +95,7 @@ int main(int, char**)
     static_assert(!std::is_invocable_v<L, bool>);
     static_assert(!std::is_invocable_v<L, char>);
     static_assert(!std::is_invocable_v<L, wchar_t>);
-#ifndef _LIBCPP_HAS_NO_CHAR8_T
+#ifndef TEST_HAS_NO_CHAR8_T
     static_assert(!std::is_invocable_v<L, char8_t>);
 #endif
     static_assert(!std::is_invocable_v<L, char16_t>);
diff --git a/libcxx/test/std/numerics/bit/bitops.count/countr_zero.pass.cpp b/libcxx/test/std/numerics/bit/bitops.count/countr_zero.pass.cpp
index ffe5031d7e4d1..e8aa7f777acdc 100644
--- a/libcxx/test/std/numerics/bit/bitops.count/countr_zero.pass.cpp
+++ b/libcxx/test/std/numerics/bit/bitops.count/countr_zero.pass.cpp
@@ -92,7 +92,7 @@ int main(int, char**)
     static_assert(!std::is_invocable_v<L, bool>);
     static_assert(!std::is_invocable_v<L, char>);
     static_assert(!std::is_invocable_v<L, wchar_t>);
-#ifndef _LIBCPP_HAS_NO_CHAR8_T
+#ifndef TEST_HAS_NO_CHAR8_T
     static_assert(!std::is_invocable_v<L, char8_t>);
 #endif
     static_assert(!std::is_invocable_v<L, char16_t>);
diff --git a/libcxx/test/std/numerics/bit/bitops.count/popcount.pass.cpp b/libcxx/test/std/numerics/bit/bitops.count/popcount.pass.cpp
index 3dd994b0868ad..3be240fb25a56 100644
--- a/libcxx/test/std/numerics/bit/bitops.count/popcount.pass.cpp
+++ b/libcxx/test/std/numerics/bit/bitops.count/popcount.pass.cpp
@@ -102,7 +102,7 @@ int main(int, char**)
     static_assert(!std::is_invocable_v<L, bool>);
     static_assert(!std::is_invocable_v<L, char>);
     static_assert(!std::is_invocable_v<L, wchar_t>);
-#ifndef _LIBCPP_HAS_NO_CHAR8_T
+#ifndef TEST_HAS_NO_CHAR8_T
     static_assert(!std::is_invocable_v<L, char8_t>);
 #endif
     static_assert(!std::is_invocable_v<L, char16_t>);
diff --git a/libcxx/test/std/numerics/bit/bitops.rot/rotl.pass.cpp b/libcxx/test/std/numerics/bit/bitops.rot/rotl.pass.cpp
index 1432aee7fe732..78fac6267d18b 100644
--- a/libcxx/test/std/numerics/bit/bitops.rot/rotl.pass.cpp
+++ b/libcxx/test/std/numerics/bit/bitops.rot/rotl.pass.cpp
@@ -90,7 +90,7 @@ int main(int, char**)
     static_assert(!std::is_invocable_v<L, bool>);
     static_assert(!std::is_invocable_v<L, char>);
     static_assert(!std::is_invocable_v<L, wchar_t>);
-#ifndef _LIBCPP_HAS_NO_CHAR8_T
+#ifndef TEST_HAS_NO_CHAR8_T
     static_assert(!std::is_invocable_v<L, char8_t>);
 #endif
     static_assert(!std::is_invocable_v<L, char16_t>);
diff --git a/libcxx/test/std/numerics/bit/bitops.rot/rotr.pass.cpp b/libcxx/test/std/numerics/bit/bitops.rot/rotr.pass.cpp
index 8c8505a2d5882..f930f40c5d18c 100644
--- a/libcxx/test/std/numerics/bit/bitops.rot/rotr.pass.cpp
+++ b/libcxx/test/std/numerics/bit/bitops.rot/rotr.pass.cpp
@@ -91,7 +91,7 @@ int main(int, char**)
     static_assert(!std::is_invocable_v<L, bool>);
     static_assert(!std::is_invocable_v<L, char>);
     static_assert(!std::is_invocable_v<L, wchar_t>);
-#ifndef _LIBCPP_HAS_NO_CHAR8_T
+#ifndef TEST_HAS_NO_CHAR8_T
     static_assert(!std::is_invocable_v<L, char8_t>);
 #endif
     static_assert(!std::is_invocable_v<L, char16_t>);
diff --git a/libcxx/test/std/strings/string.view/trivially_copyable.compile.pass.cpp b/libcxx/test/std/strings/string.view/trivially_copyable.compile.pass.cpp
index 6a22864b23f10..e8072585a6601 100644
--- a/libcxx/test/std/strings/string.view/trivially_copyable.compile.pass.cpp
+++ b/libcxx/test/std/strings/string.view/trivially_copyable.compile.pass.cpp
@@ -19,7 +19,7 @@ static_assert(std::is_trivially_copyable<std::basic_string_view<char> >::value,
 #ifndef TEST_HAS_NO_WIDE_CHARACTERS
 static_assert(std::is_trivially_copyable<std::basic_string_view<wchar_t> >::value, "");
 #endif
-#ifndef _LIBCPP_HAS_NO_CHAR8_T
+#ifndef TEST_HAS_NO_CHAR8_T
 static_assert(std::is_trivially_copyable<std::basic_string_view<char8_t> >::value, "");
 #endif
 static_assert(std::is_trivially_copyable<std::basic_string_view<char16_t> >::value, "");
diff --git a/libcxx/test/std/utilities/format/format.arguments/format.arg/ctor.pass.cpp b/libcxx/test/std/utilities/format/format.arguments/format.arg/ctor.pass.cpp
index 56fb05f1ad233..a15fe91ff638b 100644
--- a/libcxx/test/std/utilities/format/format.arguments/format.arg/ctor.pass.cpp
+++ b/libcxx/test/std/utilities/format/format.arguments/format.arg/ctor.pass.cpp
@@ -34,7 +34,7 @@ void test() {
 void test() {
   test<char>();
   test<wchar_t>();
-#ifndef _LIBCPP_HAS_NO_CHAR8_T
+#ifndef TEST_HAS_NO_CHAR8_T
   test<char8_t>();
 #endif
 #ifndef TEST_HAS_NO_UNICODE_CHARS
diff --git a/libcxx/test/std/utilities/format/format.formatter/format.context/format.context/advance_to.pass.cpp b/libcxx/test/std/utilities/format/format.formatter/format.context/format.context/advance_to.pass.cpp
index a2afa786e0bb6..14b430580060b 100644
--- a/libcxx/test/std/utilities/format/format.formatter/format.context/format.context/advance_to.pass.cpp
+++ b/libcxx/test/std/utilities/format/format.formatter/format.context/format.context/advance_to.pass.cpp
@@ -52,7 +52,7 @@ void test() {
       std::make_format_args<std::basic_format_context<
           std::back_insert_iterator<std::basic_string<wchar_t>>, wchar_t>>()));
 #endif
-#ifndef _LIBCPP_HAS_NO_CHAR8_T
+#ifndef TEST_HAS_NO_CHAR8_T
   test(std::basic_format_args(
       std::make_format_args<std::basic_format_context<
           std::back_insert_iterator<std::basic_string<char8_t>>, char8_t>>()));
diff --git a/libcxx/test/std/utilities/format/format.formatter/format.context/format.context/arg.pass.cpp b/libcxx/test/std/utilities/format/format.formatter/format.context/format.context/arg.pass.cpp
index 3b4834110e847..8e8afa9edc405 100644
--- a/libcxx/test/std/utilities/format/format.formatter/format.context/format.context/arg.pass.cpp
+++ b/libcxx/test/std/utilities/format/format.formatter/format.context/format.context/arg.pass.cpp
@@ -51,7 +51,7 @@ int main(int, char**) {
 #ifndef TEST_HAS_NO_WIDE_CHARACTERS
   test<std::back_insert_iterator<std::basic_string<wchar_t>>, wchar_t>();
 #endif
-#ifndef _LIBCPP_HAS_NO_CHAR8_T
+#ifndef TEST_HAS_NO_CHAR8_T
   test<std::back_insert_iterator<std::basic_string<char8_t>>, char8_t>();
 #endif
 #ifndef TEST_HAS_NO_UNICODE_CHARS
diff --git a/libcxx/test/std/utilities/format/format.formatter/format.context/format.context/ctor.pass.cpp b/libcxx/test/std/utilities/format/format.formatter/format.context/format.context/ctor.pass.cpp
index 049672f30f1db..e56d872670644 100644
--- a/libcxx/test/std/utilities/format/format.formatter/format.context/format.context/ctor.pass.cpp
+++ b/libcxx/test/std/utilities/format/format.formatter/format.context/format.context/ctor.pass.cpp
@@ -129,7 +129,7 @@ void test() {
 #ifndef TEST_HAS_NO_WIDE_CHARACTERS
   test<std::back_insert_iterator<std::basic_string<wchar_t>>, wchar_t>();
 #endif
-#ifndef _LIBCPP_HAS_NO_CHAR8_T
+#ifndef TEST_HAS_NO_CHAR8_T
   test<std::back_insert_iterator<std::basic_string<char8_t>>, char8_t>();
 #endif
 #ifndef TEST_HAS_NO_UNICODE_CHARS
diff --git a/libcxx/test/std/utilities/format/format.formatter/format.context/format.context/locale.pass.cpp b/libcxx/test/std/utilities/format/format.formatter/format.context/format.context/locale.pass.cpp
index 3286991e69fd3..6a85d3de0cdd3 100644
--- a/libcxx/test/std/utilities/format/format.formatter/format.context/format.context/locale.pass.cpp
+++ b/libcxx/test/std/utilities/format/format.formatter/format.context/format.context/locale.pass.cpp
@@ -85,7 +85,7 @@ void test() {
 #ifndef TEST_HAS_NO_WIDE_CHARACTERS
   test<std::back_insert_iterator<std::basic_string<wchar_t>>, wchar_t>();
 #endif
-#ifndef _LIBCPP_HAS_NO_CHAR8_T
+#ifndef TEST_HAS_NO_CHAR8_T
   test<std::back_insert_iterator<std::basic_string<char8_t>>, char8_t>();
 #endif
 #ifndef TEST_HAS_NO_UNICODE_CHARS
diff --git a/libcxx/test/std/utilities/format/format.formatter/format.context/format.context/out.pass.cpp b/libcxx/test/std/utilities/format/format.formatter/format.context/format.context/out.pass.cpp
index b211dfd3e7fab..506c485d4a5b2 100644
--- a/libcxx/test/std/utilities/format/format.formatter/format.context/format.context/out.pass.cpp
+++ b/libcxx/test/std/utilities/format/format.formatter/format.context/format.context/out.pass.cpp
@@ -48,7 +48,7 @@ void test() {
       std::make_format_args<std::basic_format_context<
           std::back_insert_iterator<std::basic_string<wchar_t>>, wchar_t>>()));
 #endif
-#ifndef _LIBCPP_HAS_NO_CHAR8_T
+#ifndef TEST_HAS_NO_CHAR8_T
   test(std::basic_format_args(
       std::make_format_args<std::basic_format_context<
           std::back_insert_iterator<std::basic_string<char8_t>>, char8_t>>()));
diff --git a/libcxx/test/std/utilities/format/format.formatter/format.parse.ctx/advance_to.pass.cpp b/libcxx/test/std/utilities/format/format.formatter/format.parse.ctx/advance_to.pass.cpp
index 88c7cf5171898..7bb0d3e26610c 100644
--- a/libcxx/test/std/utilities/format/format.formatter/format.parse.ctx/advance_to.pass.cpp
+++ b/libcxx/test/std/utilities/format/format.formatter/format.parse.ctx/advance_to.pass.cpp
@@ -52,7 +52,7 @@ constexpr void test(const CharT* fmt) {
 constexpr bool test() {
   test("abc");
   test(L"abc");
-#ifndef _LIBCPP_HAS_NO_CHAR8_T
+#ifndef TEST_HAS_NO_CHAR8_T
   test(u8"abc");
 #endif
 #ifndef TEST_HAS_NO_UNICODE_CHARS
diff --git a/libcxx/test/std/utilities/format/format.formatter/format.parse.ctx/begin.pass.cpp b/libcxx/test/std/utilities/format/format.formatter/format.parse.ctx/begin.pass.cpp
index c78c995543179..fd209e611c6bc 100644
--- a/libcxx/test/std/utilities/format/format.formatter/format.parse.ctx/begin.pass.cpp
+++ b/libcxx/test/std/utilities/format/format.formatter/format.parse.ctx/begin.pass.cpp
@@ -38,7 +38,7 @@ constexpr void test(const CharT* fmt) {
 constexpr bool test() {
   test("abc");
   test(L"abc");
-#ifndef _LIBCPP_HAS_NO_CHAR8_T
+#ifndef TEST_HAS_NO_CHAR8_T
   test(u8"abc");
 #endif
 #ifndef TEST_HAS_NO_UNICODE_CHARS
diff --git a/libcxx/test/std/utilities/format/format.formatter/format.parse.ctx/ctor.pass.cpp b/libcxx/test/std/utilities/format/format.formatter/format.parse.ctx/ctor.pass.cpp
index e11d000f0e902..195f07742a016 100644
--- a/libcxx/test/std/utilities/format/format.formatter/format.parse.ctx/ctor.pass.cpp
+++ b/libcxx/test/std/utilities/format/format.formatter/format.parse.ctx/ctor.pass.cpp
@@ -61,7 +61,7 @@ constexpr void test(const CharT* fmt) {
 constexpr bool test() {
   test("abc");
   test(L"abc");
-#ifndef _LIBCPP_HAS_NO_CHAR8_T
+#ifndef TEST_HAS_NO_CHAR8_T
   test(u8"abc");
 #endif
 #ifndef TEST_HAS_NO_UNICODE_CHARS
diff --git a/libcxx/test/std/utilities/format/format.formatter/format.parse.ctx/end.pass.cpp b/libcxx/test/std/utilities/format/format.formatter/format.parse.ctx/end.pass.cpp
index 9f6c8dc65c6a9..9a878ef42ba18 100644
--- a/libcxx/test/std/utilities/format/format.formatter/format.parse.ctx/end.pass.cpp
+++ b/libcxx/test/std/utilities/format/format.formatter/format.parse.ctx/end.pass.cpp
@@ -38,7 +38,7 @@ constexpr void test(const CharT* fmt) {
 constexpr bool test() {
   test("abc");
   test(L"abc");
-#ifndef _LIBCPP_HAS_NO_CHAR8_T
+#ifndef TEST_HAS_NO_CHAR8_T
   test(u8"abc");
 #endif
 #ifndef TEST_HAS_NO_UNICODE_CHARS
diff --git a/libcxx/test/std/utilities/format/format.formatter/format.parse.ctx/types.compile.pass.cpp b/libcxx/test/std/utilities/format/format.formatter/format.parse.ctx/types.compile.pass.cpp
index 412bff7f2c91a..bc1398266b6c3 100644
--- a/libcxx/test/std/utilities/format/format.formatter/format.parse.ctx/types.compile.pass.cpp
+++ b/libcxx/test/std/utilities/format/format.formatter/format.parse.ctx/types.compile.pass.cpp
@@ -50,7 +50,7 @@ constexpr void test() {
 #ifndef TEST_HAS_NO_WIDE_CHARACTERS
   test<wchar_t>();
 #endif
-#ifndef _LIBCPP_HAS_NO_CHAR8_T
+#ifndef TEST_HAS_NO_CHAR8_T
   test<char8_t>();
 #endif
 #ifndef TEST_HAS_NO_UNICODE_CHARS
diff --git a/libcxx/test/std/utilities/utility/utility.intcmp/intcmp.fail.cpp b/libcxx/test/std/utilities/utility/utility.intcmp/intcmp.fail.cpp
index e822e73210872..a399cc7c1aee6 100644
--- a/libcxx/test/std/utilities/utility/utility.intcmp/intcmp.fail.cpp
+++ b/libcxx/test/std/utilities/utility/utility.intcmp/intcmp.fail.cpp
@@ -72,7 +72,7 @@ constexpr void test() {
   std::in_range<T>(int()); // expected-error 10-11 {{no matching function for call to 'in_range'}}
   std::in_range<int>(T()); // expected-error 10-11 {{no matching function for call to 'in_range'}}
 }
-#ifndef _LIBCPP_HAS_NO_CHAR8_T
+#ifndef TEST_HAS_NO_CHAR8_T
 template <class T>
 constexpr void test_char8t() {
   std::cmp_equal(T(), T()); // expected-error 1 {{no matching function for call to 'cmp_equal'}}
@@ -96,7 +96,7 @@ constexpr void test_char8t() {
   std::in_range<T>(int()); // expected-error 1 {{no matching function for call to 'in_range'}}
   std::in_range<int>(T()); // expected-error 1 {{no matching function for call to 'in_range'}}
 }
-#endif // _LIBCPP_HAS_NO_CHAR8_T
+#endif // TEST_HAS_NO_CHAR8_T
 
 #ifndef TEST_HAS_NO_UNICODE_CHARS
 template <class T>
@@ -139,9 +139,9 @@ int main(int, char**) {
   test<std::nullptr_t>();
   test<EmptyT>();
 
-#ifndef _LIBCPP_HAS_NO_CHAR8_T
+#ifndef TEST_HAS_NO_CHAR8_T
   test_char8t<char8_t>();
-#endif // _LIBCPP_HAS_NO_CHAR8_T
+#endif // TEST_HAS_NO_CHAR8_T
 
 #ifndef TEST_HAS_NO_UNICODE_CHARS
   test_uchars<char16_t>();
diff --git a/libcxx/test/support/test_macros.h b/libcxx/test/support/test_macros.h
index c3794ab4685dd..321347f801c76 100644
--- a/libcxx/test/support/test_macros.h
+++ b/libcxx/test/support/test_macros.h
@@ -380,6 +380,10 @@ inline void DoNotOptimize(Tp const& value) {
 #  define TEST_HAS_NO_LOCALIZATION
 #endif
 
+#if TEST_STD_VER <= 17 || !defined(__cpp_char8_t)
+#  define TEST_HAS_NO_CHAR8_T
+#endif
+
 #if defined(__GNUC__)
 #pragma GCC diagnostic pop
 #endif