Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 2801 insertions, 0 deletions

diff --git a/xpcom/tests/gtest/TestStrings.cpp b/xpcom/tests/gtest/TestStrings.cpp
new file mode 100644
index 0000000000..7e0f986d29
--- /dev/null
+++ b/xpcom/tests/gtest/TestStrings.cpp
@@ -0,0 +1,2801 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include "nsASCIIMask.h"
+#include "nsCharSeparatedTokenizer.h"
+#include "nsPrintfCString.h"
+#include "nsString.h"
+#include "nsStringBuffer.h"
+#include "nsReadableUtils.h"
+#include "nsCRTGlue.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/TextUtils.h"
+#include "mozilla/Unused.h"
+#include "mozilla/Utf8.h"
+#include "nsTArray.h"
+#include "gtest/gtest.h"
+#include "gtest/MozGTestBench.h"  // For MOZ_GTEST_BENCH
+#include "gtest/BlackBox.h"
+#include "nsBidiUtils.h"
+#include "js/String.h"
+
+#define CONVERSION_ITERATIONS 50000
+
+#define CONVERSION_BENCH(name, func, src, dstType)    \
+  MOZ_GTEST_BENCH_F(Strings, name, [this] {           \
+    for (int i = 0; i < CONVERSION_ITERATIONS; i++) { \
+      dstType dst;                                    \
+      func(*BlackBox(&src), *BlackBox(&dst));         \
+    }                                                 \
+  });
+
+// Disable the C++ 2a warning. See bug #1509926
+#if defined(__clang__) && (__clang_major__ >= 6)
+#  pragma clang diagnostic push
+#  pragma clang diagnostic ignored "-Wc++2a-compat"
+#endif
+
+namespace TestStrings {
+
+using mozilla::BlackBox;
+using mozilla::fallible;
+using mozilla::IsAscii;
+using mozilla::IsUtf8;
+using mozilla::Maybe;
+using mozilla::Nothing;
+using mozilla::Some;
+using mozilla::Span;
+
+#define TestExample1                                                           \
+  "Sed ut perspiciatis unde omnis iste natus error sit voluptatem "            \
+  "accusantium doloremque laudantium,\n totam rem aperiam, eaque ipsa quae "   \
+  "ab illo inventore veritatis et quasi\r architecto beatae vitae dicta sunt " \
+  "explicabo. Nemo enim ipsam voluptatem quia voluptas sit aspernatur\n aut "  \
+  "odit aut fugit, sed quia consequuntur magni dolores eos qui ratione "       \
+  "voluptatem sequi nesciunt. Neque porro quisquam est, qui\r\n\r dolorem "    \
+  "ipsum quia dolor sit amet, consectetur, adipisci velit, sed quia non "      \
+  "numquam eius modi tempora incidunt ut labore et dolore magnam aliquam "     \
+  "quaerat voluptatem. Ut enim ad minima veniam, quis nostrum exercitationem " \
+  "ullam corporis suscipit laboriosam, nisi ut aliquid ex ea commodi "         \
+  "consequatur? Quis autem vel eum iure reprehenderit qui in ea voluptate "    \
+  "velit esse quam nihil molestiae consequatur, vel illum qui dolorem eum "    \
+  "fugiat quo voluptas nulla pariatur?"
+
+#define TestExample2                                                           \
+  "At vero eos et accusamus et iusto odio dignissimos ducimus\n\n qui "        \
+  "blanditiis praesentium voluptatum deleniti atque corrupti quos dolores et " \
+  "quas molestias excepturi sint occaecati cupiditate non provident, "         \
+  "similique sunt in culpa qui officia deserunt\r\r  \n mollitia animi, id "   \
+  "est laborum et dolorum fuga. Et harum quidem rerum facilis est et "         \
+  "expedita distinctio. Nam libero tempore, cum soluta nobis est eligendi "    \
+  "optio cumque nihil impedit quo minus id quod maxime placeat facere "        \
+  "possimus, omnis voluptas assumenda       est, omnis dolor repellendus. "    \
+  "Temporibus autem quibusdam et aut officiis debitis aut rerum "              \
+  "necessitatibus saepe eveniet ut et voluptates repudiandae sint et "         \
+  "molestiae non recusandae. Itaque earum rerum hic tenetur a sapiente "       \
+  "delectus, ut aut reiciendis voluptatibus maiores alias consequatur aut "    \
+  "perferendis doloribus asperiores repellat."
+
+#define TestExample3                                                           \
+  " Lorem ipsum dolor sit amet, consectetur adipiscing elit. Duis ac tellus "  \
+  "eget velit viverra viverra id sit amet neque. Sed id consectetur mi, "      \
+  "vestibulum aliquet arcu. Curabitur sagittis accumsan convallis. Sed eu "    \
+  "condimentum ipsum, a laoreet tortor. Orci varius natoque penatibus et "     \
+  "magnis dis    \r\r\n\n parturient montes, nascetur ridiculus mus. Sed non " \
+  "tellus nec ante sodales placerat a nec risus. Cras vel bibendum sapien, "   \
+  "nec ullamcorper felis. Pellentesque congue eget nisi sit amet vehicula. "   \
+  "Morbi pulvinar turpis justo, in commodo dolor vulputate id. Curabitur in "  \
+  "dui urna. Vestibulum placerat dui in sem congue, ut faucibus nibh rutrum. " \
+  "Duis mattis turpis facilisis ullamcorper tincidunt. Vestibulum pharetra "   \
+  "tortor at enim sagittis, dapibus consectetur ex blandit. Curabitur ac "     \
+  "fringilla quam. In ornare lectus ut ipsum mattis venenatis. Etiam in "      \
+  "mollis lectus, sed luctus risus.\nCras dapibus\f\t  \n finibus justo sit "  \
+  "amet dictum. Aliquam non elit diam. Fusce magna nulla, bibendum in massa "  \
+  "a, commodo finibus lectus. Sed rutrum a augue id imperdiet. Aliquam "       \
+  "sagittis sodales felis, a tristique ligula. Aliquam erat volutpat. "        \
+  "Pellentesque habitant morbi tristique senectus et netus et malesuada "      \
+  "fames ac turpis egestas. Duis volutpat interdum lorem et congue. "          \
+  "Phasellus porttitor posuere justo eget euismod. Nam a condimentum turpis, " \
+  "sit amet gravida lacus. Vestibulum dolor diam, lobortis ac metus et, "      \
+  "convallis dapibus tellus. Ut nec metus in velit malesuada tincidunt et "    \
+  "eget justo. Curabitur ut libero bibendum, porttitor diam vitae, aliquet "   \
+  "justo. "
+
+#define TestExample4                                                           \
+  " Donec feugiat volutpat massa. Cras ornare lacinia porta. Fusce in "        \
+  "feugiat nunc. Praesent non felis varius diam feugiat ultrices ultricies a " \
+  "risus. Donec maximus nisi nisl, non consectetur nulla eleifend in. Nulla "  \
+  "in massa interdum, eleifend orci a, vestibulum est. Mauris aliquet, massa " \
+  "et convallis mollis, felis augue vestibulum augue, in lobortis metus eros " \
+  "a quam. Nam              ac diam ornare, vestibulum elit sit amet, "        \
+  "consectetur ante. Praesent massa mauris, pulvinar sit amet sapien vel, "    \
+  "tempus gravida neque. Praesent id quam sit amet est maximus molestie eget " \
+  "at turpis. Nunc sit amet orci id arcu dapibus fermentum non eu "            \
+  "erat.\f\tSuspendisse commodo nunc sem, eu congue eros condimentum vel. "    \
+  "Nullam sit amet posuere arcu. Nulla facilisi. Mauris dapibus iaculis "      \
+  "massa sed gravida. Nullam vitae urna at tortor feugiat auctor ut sit amet " \
+  "dolor. Proin rutrum at nunc et faucibus. Quisque suscipit id nibh a "       \
+  "aliquet. Pellentesque habitant morbi tristique senectus et netus et "       \
+  "malesuada fames ac turpis egestas. Aliquam a dapibus erat, id imperdiet "   \
+  "mauris. Nulla blandit libero non magna dapibus tristique. Integer "         \
+  "hendrerit imperdiet lorem, quis facilisis lacus semper ut. Vestibulum "     \
+  "ante ipsum primis in faucibus orci luctus et ultrices posuere cubilia "     \
+  "Curae Nullam dignissim elit in congue ultricies. Quisque erat odio, "       \
+  "maximus mollis laoreet id, iaculis at turpis. "
+
+#define TestExample5                                                          \
+  "Donec id risus urna. Nunc consequat lacinia urna id bibendum. Nulla "      \
+  "faucibus faucibus enim. Cras ex risus, ultrices id semper vitae, luctus "  \
+  "ut nulla. Sed vehicula tellus sed purus imperdiet efficitur. Suspendisse " \
+  "feugiat\n\n\n     imperdiet odio, sed porta lorem feugiat nec. Curabitur " \
+  "laoreet massa venenatis\r\n risus ornare\r\n, vitae feugiat tortor "       \
+  "accumsan. Lorem ipsum dolor sit amet, consectetur adipiscing elit. "       \
+  "Maecenas id scelerisque mauris, eget facilisis erat. Ut nec pulvinar "     \
+  "risus, sed iaculis ante. Mauris tincidunt, risus et pretium elementum, "   \
+  "leo nisi consectetur ligula, tincidunt suscipit erat velit eget libero. "  \
+  "Sed ac est tempus, consequat dolor mattis, mattis mi. "
+
+// Originally ReadVPXFile in TestVPXDecoding.cpp
+static void ReadFile(const char* aPath, nsACString& aBuffer) {
+  FILE* f = fopen(aPath, "rb");
+  ASSERT_NE(f, (FILE*)nullptr);
+
+  int r = fseek(f, 0, SEEK_END);
+  ASSERT_EQ(r, 0);
+
+  long size = ftell(f);
+  ASSERT_NE(size, -1);
+  aBuffer.SetLength(size);
+
+  r = fseek(f, 0, SEEK_SET);
+  ASSERT_EQ(r, 0);
+
+  size_t got = fread(aBuffer.BeginWriting(), 1, size, f);
+  ASSERT_EQ(got, size_t(size));
+
+  r = fclose(f);
+  ASSERT_EQ(r, 0);
+}
+
+class Strings : public ::testing::Test {
+ protected:
+  void SetUp() override {
+    // Intentionally AssignASCII and not AssignLiteral
+    // to simulate the usual heap case.
+    mExample1Utf8.AssignASCII(TestExample1);
+    mExample2Utf8.AssignASCII(TestExample2);
+    mExample3Utf8.AssignASCII(TestExample3);
+    mExample4Utf8.AssignASCII(TestExample4);
+    mExample5Utf8.AssignASCII(TestExample5);
+
+    // Use span to make the resulting string as ordinary as possible
+    mAsciiOneUtf8.Append(Span(mExample3Utf8).To(1));
+    mAsciiThreeUtf8.Append(Span(mExample3Utf8).To(3));
+    mAsciiFifteenUtf8.Append(Span(mExample3Utf8).To(15));
+    mAsciiHundredUtf8.Append(Span(mExample3Utf8).To(100));
+    mAsciiThousandUtf8.Append(Span(mExample3Utf8).To(1000));
+
+    ReadFile("ar.txt", mArUtf8);
+    ReadFile("de.txt", mDeUtf8);
+    ReadFile("de-edit.txt", mDeEditUtf8);
+    ReadFile("ru.txt", mRuUtf8);
+    ReadFile("th.txt", mThUtf8);
+    ReadFile("ko.txt", mKoUtf8);
+    ReadFile("ja.txt", mJaUtf8);
+    ReadFile("tr.txt", mTrUtf8);
+    ReadFile("vi.txt", mViUtf8);
+
+    CopyASCIItoUTF16(mExample1Utf8, mExample1Utf16);
+    CopyASCIItoUTF16(mExample2Utf8, mExample2Utf16);
+    CopyASCIItoUTF16(mExample3Utf8, mExample3Utf16);
+    CopyASCIItoUTF16(mExample4Utf8, mExample4Utf16);
+    CopyASCIItoUTF16(mExample5Utf8, mExample5Utf16);
+
+    CopyASCIItoUTF16(mAsciiOneUtf8, mAsciiOneUtf16);
+    CopyASCIItoUTF16(mAsciiFifteenUtf8, mAsciiFifteenUtf16);
+    CopyASCIItoUTF16(mAsciiHundredUtf8, mAsciiHundredUtf16);
+    CopyASCIItoUTF16(mAsciiThousandUtf8, mAsciiThousandUtf16);
+
+    CopyUTF8toUTF16(mArUtf8, mArUtf16);
+    CopyUTF8toUTF16(mDeUtf8, mDeUtf16);
+    CopyUTF8toUTF16(mDeEditUtf8, mDeEditUtf16);
+    CopyUTF8toUTF16(mRuUtf8, mRuUtf16);
+    CopyUTF8toUTF16(mThUtf8, mThUtf16);
+    CopyUTF8toUTF16(mJaUtf8, mJaUtf16);
+    CopyUTF8toUTF16(mKoUtf8, mKoUtf16);
+    CopyUTF8toUTF16(mTrUtf8, mTrUtf16);
+    CopyUTF8toUTF16(mViUtf8, mViUtf16);
+
+    LossyCopyUTF16toASCII(mDeEditUtf16, mDeEditLatin1);
+
+    // Use span to make the resulting string as ordinary as possible
+    mArOneUtf16.Append(Span(mArUtf16).To(1));
+    mDeOneUtf16.Append(Span(mDeUtf16).To(1));
+    mDeEditOneUtf16.Append(Span(mDeEditUtf16).To(1));
+    mRuOneUtf16.Append(Span(mRuUtf16).To(1));
+    mThOneUtf16.Append(Span(mThUtf16).To(1));
+    mJaOneUtf16.Append(Span(mJaUtf16).To(1));
+    mKoOneUtf16.Append(Span(mKoUtf16).To(1));
+    mTrOneUtf16.Append(Span(mTrUtf16).To(1));
+    mViOneUtf16.Append(Span(mViUtf16).To(1));
+
+    mDeEditOneLatin1.Append(Span(mDeEditLatin1).To(1));
+
+    mArThreeUtf16.Append(Span(mArUtf16).To(3));
+    mDeThreeUtf16.Append(Span(mDeUtf16).To(3));
+    mDeEditThreeUtf16.Append(Span(mDeEditUtf16).To(3));
+    mRuThreeUtf16.Append(Span(mRuUtf16).To(3));
+    mThThreeUtf16.Append(Span(mThUtf16).To(3));
+    mJaThreeUtf16.Append(Span(mJaUtf16).To(3));
+    mKoThreeUtf16.Append(Span(mKoUtf16).To(3));
+    mTrThreeUtf16.Append(Span(mTrUtf16).To(3));
+    mViThreeUtf16.Append(Span(mViUtf16).To(3));
+
+    mDeEditThreeLatin1.Append(Span(mDeEditLatin1).To(3));
+
+    mArFifteenUtf16.Append(Span(mArUtf16).To(15));
+    mDeFifteenUtf16.Append(Span(mDeUtf16).To(15));
+    mDeEditFifteenUtf16.Append(Span(mDeEditUtf16).To(15));
+    mRuFifteenUtf16.Append(Span(mRuUtf16).To(15));
+    mThFifteenUtf16.Append(Span(mThUtf16).To(15));
+    mJaFifteenUtf16.Append(Span(mJaUtf16).To(15));
+    mKoFifteenUtf16.Append(Span(mKoUtf16).To(15));
+    mTrFifteenUtf16.Append(Span(mTrUtf16).To(15));
+    mViFifteenUtf16.Append(Span(mViUtf16).To(15));
+
+    mDeEditFifteenLatin1.Append(Span(mDeEditLatin1).To(15));
+
+    mArHundredUtf16.Append(Span(mArUtf16).To(100));
+    mDeHundredUtf16.Append(Span(mDeUtf16).To(100));
+    mDeEditHundredUtf16.Append(Span(mDeEditUtf16).To(100));
+    mRuHundredUtf16.Append(Span(mRuUtf16).To(100));
+    mThHundredUtf16.Append(Span(mThUtf16).To(100));
+    mJaHundredUtf16.Append(Span(mJaUtf16).To(100));
+    mKoHundredUtf16.Append(Span(mKoUtf16).To(100));
+    mTrHundredUtf16.Append(Span(mTrUtf16).To(100));
+    mViHundredUtf16.Append(Span(mViUtf16).To(100));
+
+    mDeEditHundredLatin1.Append(Span(mDeEditLatin1).To(100));
+
+    mArThousandUtf16.Append(Span(mArUtf16).To(1000));
+    mDeThousandUtf16.Append(Span(mDeUtf16).To(1000));
+    mDeEditThousandUtf16.Append(Span(mDeEditUtf16).To(1000));
+    mRuThousandUtf16.Append(Span(mRuUtf16).To(1000));
+    mThThousandUtf16.Append(Span(mThUtf16).To(1000));
+    mJaThousandUtf16.Append(Span(mJaUtf16).To(1000));
+    mKoThousandUtf16.Append(Span(mKoUtf16).To(1000));
+    mTrThousandUtf16.Append(Span(mTrUtf16).To(1000));
+    mViThousandUtf16.Append(Span(mViUtf16).To(1000));
+
+    mDeEditThousandLatin1.Append(Span(mDeEditLatin1).To(1000));
+
+    CopyUTF16toUTF8(mArOneUtf16, mArOneUtf8);
+    CopyUTF16toUTF8(mDeOneUtf16, mDeOneUtf8);
+    CopyUTF16toUTF8(mDeEditOneUtf16, mDeEditOneUtf8);
+    CopyUTF16toUTF8(mRuOneUtf16, mRuOneUtf8);
+    CopyUTF16toUTF8(mThOneUtf16, mThOneUtf8);
+    CopyUTF16toUTF8(mJaOneUtf16, mJaOneUtf8);
+    CopyUTF16toUTF8(mKoOneUtf16, mKoOneUtf8);
+    CopyUTF16toUTF8(mTrOneUtf16, mTrOneUtf8);
+    CopyUTF16toUTF8(mViOneUtf16, mViOneUtf8);
+
+    CopyUTF16toUTF8(mArThreeUtf16, mArThreeUtf8);
+    CopyUTF16toUTF8(mDeThreeUtf16, mDeThreeUtf8);
+    CopyUTF16toUTF8(mDeEditThreeUtf16, mDeEditThreeUtf8);
+    CopyUTF16toUTF8(mRuThreeUtf16, mRuThreeUtf8);
+    CopyUTF16toUTF8(mThThreeUtf16, mThThreeUtf8);
+    CopyUTF16toUTF8(mJaThreeUtf16, mJaThreeUtf8);
+    CopyUTF16toUTF8(mKoThreeUtf16, mKoThreeUtf8);
+    CopyUTF16toUTF8(mTrThreeUtf16, mTrThreeUtf8);
+    CopyUTF16toUTF8(mViThreeUtf16, mViThreeUtf8);
+
+    CopyUTF16toUTF8(mArFifteenUtf16, mArFifteenUtf8);
+    CopyUTF16toUTF8(mDeFifteenUtf16, mDeFifteenUtf8);
+    CopyUTF16toUTF8(mDeEditFifteenUtf16, mDeEditFifteenUtf8);
+    CopyUTF16toUTF8(mRuFifteenUtf16, mRuFifteenUtf8);
+    CopyUTF16toUTF8(mThFifteenUtf16, mThFifteenUtf8);
+    CopyUTF16toUTF8(mJaFifteenUtf16, mJaFifteenUtf8);
+    CopyUTF16toUTF8(mKoFifteenUtf16, mKoFifteenUtf8);
+    CopyUTF16toUTF8(mTrFifteenUtf16, mTrFifteenUtf8);
+    CopyUTF16toUTF8(mViFifteenUtf16, mViFifteenUtf8);
+
+    CopyUTF16toUTF8(mArHundredUtf16, mArHundredUtf8);
+    CopyUTF16toUTF8(mDeHundredUtf16, mDeHundredUtf8);
+    CopyUTF16toUTF8(mDeEditHundredUtf16, mDeEditHundredUtf8);
+    CopyUTF16toUTF8(mRuHundredUtf16, mRuHundredUtf8);
+    CopyUTF16toUTF8(mThHundredUtf16, mThHundredUtf8);
+    CopyUTF16toUTF8(mJaHundredUtf16, mJaHundredUtf8);
+    CopyUTF16toUTF8(mKoHundredUtf16, mKoHundredUtf8);
+    CopyUTF16toUTF8(mTrHundredUtf16, mTrHundredUtf8);
+    CopyUTF16toUTF8(mViHundredUtf16, mViHundredUtf8);
+
+    CopyUTF16toUTF8(mArThousandUtf16, mArThousandUtf8);
+    CopyUTF16toUTF8(mDeThousandUtf16, mDeThousandUtf8);
+    CopyUTF16toUTF8(mDeEditThousandUtf16, mDeEditThousandUtf8);
+    CopyUTF16toUTF8(mRuThousandUtf16, mRuThousandUtf8);
+    CopyUTF16toUTF8(mThThousandUtf16, mThThousandUtf8);
+    CopyUTF16toUTF8(mJaThousandUtf16, mJaThousandUtf8);
+    CopyUTF16toUTF8(mKoThousandUtf16, mKoThousandUtf8);
+    CopyUTF16toUTF8(mTrThousandUtf16, mTrThousandUtf8);
+    CopyUTF16toUTF8(mViThousandUtf16, mViThousandUtf8);
+  }
+
+ public:
+  nsCString mAsciiOneUtf8;
+  nsCString mAsciiThreeUtf8;
+  nsCString mAsciiFifteenUtf8;
+  nsCString mAsciiHundredUtf8;
+  nsCString mAsciiThousandUtf8;
+  nsCString mExample1Utf8;
+  nsCString mExample2Utf8;
+  nsCString mExample3Utf8;
+  nsCString mExample4Utf8;
+  nsCString mExample5Utf8;
+  nsCString mArUtf8;
+  nsCString mDeUtf8;
+  nsCString mDeEditUtf8;
+  nsCString mRuUtf8;
+  nsCString mThUtf8;
+  nsCString mJaUtf8;
+  nsCString mKoUtf8;
+  nsCString mTrUtf8;
+  nsCString mViUtf8;
+
+  nsString mAsciiOneUtf16;
+  nsString mAsciiThreeUtf16;
+  nsString mAsciiFifteenUtf16;
+  nsString mAsciiHundredUtf16;
+  nsString mAsciiThousandUtf16;
+  nsString mExample1Utf16;
+  nsString mExample2Utf16;
+  nsString mExample3Utf16;
+  nsString mExample4Utf16;
+  nsString mExample5Utf16;
+  nsString mArUtf16;
+  nsString mDeUtf16;
+  nsString mDeEditUtf16;
+  nsString mRuUtf16;
+  nsString mThUtf16;
+  nsString mJaUtf16;
+  nsString mKoUtf16;
+  nsString mTrUtf16;
+  nsString mViUtf16;
+
+  nsCString mDeEditLatin1;
+
+  nsString mArOneUtf16;
+  nsString mDeOneUtf16;
+  nsString mDeEditOneUtf16;
+  nsString mRuOneUtf16;
+  nsString mThOneUtf16;
+  nsString mJaOneUtf16;
+  nsString mKoOneUtf16;
+  nsString mTrOneUtf16;
+  nsString mViOneUtf16;
+
+  nsCString mDeEditOneLatin1;
+
+  nsCString mArOneUtf8;
+  nsCString mDeOneUtf8;
+  nsCString mDeEditOneUtf8;
+  nsCString mRuOneUtf8;
+  nsCString mThOneUtf8;
+  nsCString mJaOneUtf8;
+  nsCString mKoOneUtf8;
+  nsCString mTrOneUtf8;
+  nsCString mViOneUtf8;
+
+  nsString mArThreeUtf16;
+  nsString mDeThreeUtf16;
+  nsString mDeEditThreeUtf16;
+  nsString mRuThreeUtf16;
+  nsString mThThreeUtf16;
+  nsString mJaThreeUtf16;
+  nsString mKoThreeUtf16;
+  nsString mTrThreeUtf16;
+  nsString mViThreeUtf16;
+
+  nsCString mDeEditThreeLatin1;
+
+  nsCString mArThreeUtf8;
+  nsCString mDeThreeUtf8;
+  nsCString mDeEditThreeUtf8;
+  nsCString mRuThreeUtf8;
+  nsCString mThThreeUtf8;
+  nsCString mJaThreeUtf8;
+  nsCString mKoThreeUtf8;
+  nsCString mTrThreeUtf8;
+  nsCString mViThreeUtf8;
+
+  nsString mArFifteenUtf16;
+  nsString mDeFifteenUtf16;
+  nsString mDeEditFifteenUtf16;
+  nsString mRuFifteenUtf16;
+  nsString mThFifteenUtf16;
+  nsString mJaFifteenUtf16;
+  nsString mKoFifteenUtf16;
+  nsString mTrFifteenUtf16;
+  nsString mViFifteenUtf16;
+
+  nsCString mDeEditFifteenLatin1;
+
+  nsCString mArFifteenUtf8;
+  nsCString mDeFifteenUtf8;
+  nsCString mDeEditFifteenUtf8;
+  nsCString mRuFifteenUtf8;
+  nsCString mThFifteenUtf8;
+  nsCString mJaFifteenUtf8;
+  nsCString mKoFifteenUtf8;
+  nsCString mTrFifteenUtf8;
+  nsCString mViFifteenUtf8;
+
+  nsString mArHundredUtf16;
+  nsString mDeHundredUtf16;
+  nsString mDeEditHundredUtf16;
+  nsString mRuHundredUtf16;
+  nsString mThHundredUtf16;
+  nsString mJaHundredUtf16;
+  nsString mKoHundredUtf16;
+  nsString mTrHundredUtf16;
+  nsString mViHundredUtf16;
+
+  nsCString mDeEditHundredLatin1;
+
+  nsCString mArHundredUtf8;
+  nsCString mDeHundredUtf8;
+  nsCString mDeEditHundredUtf8;
+  nsCString mRuHundredUtf8;
+  nsCString mThHundredUtf8;
+  nsCString mJaHundredUtf8;
+  nsCString mKoHundredUtf8;
+  nsCString mTrHundredUtf8;
+  nsCString mViHundredUtf8;
+
+  nsString mArThousandUtf16;
+  nsString mDeThousandUtf16;
+  nsString mDeEditThousandUtf16;
+  nsString mRuThousandUtf16;
+  nsString mThThousandUtf16;
+  nsString mJaThousandUtf16;
+  nsString mKoThousandUtf16;
+  nsString mTrThousandUtf16;
+  nsString mViThousandUtf16;
+
+  nsCString mDeEditThousandLatin1;
+
+  nsCString mArThousandUtf8;
+  nsCString mDeThousandUtf8;
+  nsCString mDeEditThousandUtf8;
+  nsCString mRuThousandUtf8;
+  nsCString mThThousandUtf8;
+  nsCString mJaThousandUtf8;
+  nsCString mKoThousandUtf8;
+  nsCString mTrThousandUtf8;
+  nsCString mViThousandUtf8;
+};
+
+static void test_assign_helper(const nsACString& in, nsACString& _retval) {
+  _retval = in;
+}
+
+// Simple helper struct to test if conditionally enabled string functions are
+// working.
+template <typename T>
+struct EnableTest {
+  template <typename Q = T, typename EnableIfChar16 = mozilla::Char16OnlyT<Q>>
+  bool IsChar16() {
+    return true;
+  }
+
+  template <typename Q = T, typename EnableIfChar = mozilla::CharOnlyT<Q>>
+  bool IsChar16(int dummy = 42) {
+    return false;
+  }
+
+  template <typename Q = T, typename EnableIfChar16 = mozilla::Char16OnlyT<Q>>
+  bool IsChar() {
+    return false;
+  }
+
+  template <typename Q = T, typename EnableIfChar = mozilla::CharOnlyT<Q>>
+  bool IsChar(int dummy = 42) {
+    return true;
+  }
+};
+
+TEST_F(Strings, IsChar) {
+  EnableTest<char> charTest;
+  EXPECT_TRUE(charTest.IsChar());
+  EXPECT_FALSE(charTest.IsChar16());
+
+  EnableTest<char16_t> char16Test;
+  EXPECT_TRUE(char16Test.IsChar16());
+  EXPECT_FALSE(char16Test.IsChar());
+
+#ifdef COMPILATION_FAILURE_TEST
+  nsAutoCString a_ctest;
+  nsAutoString a_test;
+
+  a_ctest.AssignLiteral("hello");
+  // This should cause a compilation failure.
+  a_ctest.AssignLiteral(u"hello");
+  a_test.AssignLiteral(u"hello");
+  a_test.AssignLiteral("hello");
+#endif
+}
+
+TEST_F(Strings, DependentStrings) {
+  // A few tests that make sure copying nsTDependentStrings behaves properly.
+  using DataFlags = mozilla::detail::StringDataFlags;
+
+  {
+    // Test copy ctor.
+    nsDependentCString tmp("foo");
+    auto data = tmp.Data();
+    nsDependentCString foo(tmp);
+    // Neither string should be using a shared buffer.
+    EXPECT_FALSE(tmp.GetDataFlags() & DataFlags::REFCOUNTED);
+    EXPECT_FALSE(foo.GetDataFlags() & DataFlags::REFCOUNTED);
+    // Both strings should be pointing to the original buffer.
+    EXPECT_EQ(data, tmp.Data());
+    EXPECT_EQ(data, foo.Data());
+  }
+  {
+    // Test move ctor.
+    nsDependentCString tmp("foo");
+    auto data = tmp.Data();
+    nsDependentCString foo(std::move(tmp));
+    // Neither string should be using a shared buffer.
+    EXPECT_FALSE(tmp.GetDataFlags() & DataFlags::REFCOUNTED);
+    EXPECT_FALSE(foo.GetDataFlags() & DataFlags::REFCOUNTED);
+    // First string should be reset, the second should be pointing to the
+    // original buffer.
+    EXPECT_NE(data, tmp.Data());
+    EXPECT_EQ(data, foo.Data());
+    EXPECT_TRUE(tmp.IsEmpty());
+  }
+  {
+    // Test copying to a nsCString.
+    nsDependentCString tmp("foo");
+    auto data = tmp.Data();
+    nsCString foo(tmp);
+    // Original string should not be shared, copy should be shared.
+    EXPECT_FALSE(tmp.GetDataFlags() & DataFlags::REFCOUNTED);
+    EXPECT_TRUE(foo.GetDataFlags() & DataFlags::REFCOUNTED);
+    // First string should remain the same, the second should be pointing to
+    // a new buffer.
+    EXPECT_EQ(data, tmp.Data());
+    EXPECT_NE(data, foo.Data());
+  }
+}
+
+TEST_F(Strings, assign) {
+  nsCString result;
+  test_assign_helper("a"_ns + "b"_ns, result);
+  EXPECT_STREQ(result.get(), "ab");
+}
+
+TEST_F(Strings, assign_c) {
+  nsCString c;
+  c.Assign('c');
+  EXPECT_STREQ(c.get(), "c");
+}
+
+TEST_F(Strings, test1) {
+  constexpr auto empty = u""_ns;
+  const nsAString& aStr = empty;
+
+  nsAutoString buf(aStr);
+
+  int32_t n = buf.FindChar(',');
+  EXPECT_EQ(n, kNotFound);
+
+  n = buf.Length();
+
+  buf.Cut(0, n + 1);
+  n = buf.FindChar(',');
+
+  EXPECT_EQ(n, kNotFound);
+}
+
+TEST_F(Strings, test2) {
+  nsCString data("hello world");
+  const nsACString& aStr = data;
+
+  nsCString temp(aStr);
+  temp.Cut(0, 6);
+
+  EXPECT_STREQ(temp.get(), "world");
+}
+
+TEST_F(Strings, find) {
+  nsCString src("<!DOCTYPE blah blah blah>");
+
+  int32_t i = src.Find("DOCTYPE", 2);
+  EXPECT_EQ(i, 2);
+
+  i = src.Find("DOCTYPE");
+  EXPECT_EQ(i, 2);
+}
+
+TEST_F(Strings, lower_case_find) {
+  nsCString src("<!DOCTYPE blah blah blah>");
+
+  int32_t i = src.LowerCaseFindASCII("doctype", 2);
+  EXPECT_EQ(i, 2);
+
+  i = src.LowerCaseFindASCII("doctype");
+  EXPECT_EQ(i, 2);
+}
+
+TEST_F(Strings, rfind) {
+  const char text[] = "<!DOCTYPE blah bLaH bLaH>";
+  nsCString src(text);
+  int32_t i;
+
+  i = src.RFind("bLaH");
+  EXPECT_EQ(i, 20);
+
+  i = src.RFind("blah");
+  EXPECT_EQ(i, 10);
+
+  i = src.RFind("BLAH");
+  EXPECT_EQ(i, kNotFound);
+}
+
+TEST_F(Strings, rfind_2) {
+  const char text[] = "<!DOCTYPE blah blah blah>";
+  nsCString src(text);
+  int32_t i = src.RFind("TYPE");
+  EXPECT_EQ(i, 5);
+}
+
+TEST_F(Strings, rfind_3) {
+  const char text[] = "urn:mozilla:locale:en-US:necko";
+  nsAutoCString value(text);
+  int32_t i = value.RFind(":");
+  EXPECT_EQ(i, 24);
+}
+
+TEST_F(Strings, rfind_4) {
+  nsCString value("a.msf");
+  int32_t i = value.RFind(".msf");
+  EXPECT_EQ(i, 1);
+}
+
+TEST_F(Strings, findinreadable) {
+  const char text[] =
+      "jar:jar:file:///c:/software/mozilla/mozilla_2006_02_21.jar!/browser/"
+      "chrome/classic.jar!/";
+  nsAutoCString value(text);
+
+  nsACString::const_iterator begin, end;
+  value.BeginReading(begin);
+  value.EndReading(end);
+  nsACString::const_iterator delim_begin(begin), delim_end(end);
+
+  // Search for last !/ at the end of the string
+  EXPECT_TRUE(FindInReadable("!/"_ns, delim_begin, delim_end));
+  char* r = ToNewCString(Substring(delim_begin, delim_end));
+  // Should match the first "!/" but not the last
+  EXPECT_NE(delim_end, end);
+  EXPECT_STREQ(r, "!/");
+  free(r);
+
+  delim_begin = begin;
+  delim_end = end;
+
+  // Search for first jar:
+  EXPECT_TRUE(FindInReadable("jar:"_ns, delim_begin, delim_end));
+
+  r = ToNewCString(Substring(delim_begin, delim_end));
+  // Should not match the first jar:, but the second one
+  EXPECT_EQ(delim_begin, begin);
+  EXPECT_STREQ(r, "jar:");
+  free(r);
+
+  // Search for jar: in a Substring
+  delim_begin = begin;
+  delim_begin++;
+  delim_end = end;
+  EXPECT_TRUE(FindInReadable("jar:"_ns, delim_begin, delim_end));
+
+  r = ToNewCString(Substring(delim_begin, delim_end));
+  // Should not match the first jar:, but the second one
+  EXPECT_NE(delim_begin, begin);
+  EXPECT_STREQ(r, "jar:");
+  free(r);
+
+  // Should not find a match
+  EXPECT_FALSE(FindInReadable("gecko"_ns, delim_begin, delim_end));
+
+  // When no match is found, range should be empty
+  EXPECT_EQ(delim_begin, delim_end);
+
+  // Should not find a match (search not beyond Substring)
+  delim_begin = begin;
+  for (int i = 0; i < 6; i++) delim_begin++;
+  delim_end = end;
+  EXPECT_FALSE(FindInReadable("jar:"_ns, delim_begin, delim_end));
+
+  // When no match is found, range should be empty
+  EXPECT_EQ(delim_begin, delim_end);
+
+  // Should not find a match (search not beyond Substring)
+  delim_begin = begin;
+  delim_end = end;
+  for (int i = 0; i < 7; i++) delim_end--;
+  EXPECT_FALSE(FindInReadable("classic"_ns, delim_begin, delim_end));
+
+  // When no match is found, range should be empty
+  EXPECT_EQ(delim_begin, delim_end);
+}
+
+TEST_F(Strings, rfindinreadable) {
+  const char text[] =
+      "jar:jar:file:///c:/software/mozilla/mozilla_2006_02_21.jar!/browser/"
+      "chrome/classic.jar!/";
+  nsAutoCString value(text);
+
+  nsACString::const_iterator begin, end;
+  value.BeginReading(begin);
+  value.EndReading(end);
+  nsACString::const_iterator delim_begin(begin), delim_end(end);
+
+  // Search for last !/ at the end of the string
+  EXPECT_TRUE(RFindInReadable("!/"_ns, delim_begin, delim_end));
+  char* r = ToNewCString(Substring(delim_begin, delim_end));
+  // Should match the last "!/"
+  EXPECT_EQ(delim_end, end);
+  EXPECT_STREQ(r, "!/");
+  free(r);
+
+  delim_begin = begin;
+  delim_end = end;
+
+  // Search for last jar: but not the first one...
+  EXPECT_TRUE(RFindInReadable("jar:"_ns, delim_begin, delim_end));
+
+  r = ToNewCString(Substring(delim_begin, delim_end));
+  // Should not match the first jar:, but the second one
+  EXPECT_NE(delim_begin, begin);
+  EXPECT_STREQ(r, "jar:");
+  free(r);
+
+  // Search for jar: in a Substring
+  delim_begin = begin;
+  delim_end = begin;
+  for (int i = 0; i < 6; i++) delim_end++;
+  EXPECT_TRUE(RFindInReadable("jar:"_ns, delim_begin, delim_end));
+
+  r = ToNewCString(Substring(delim_begin, delim_end));
+  // Should not match the first jar:, but the second one
+  EXPECT_EQ(delim_begin, begin);
+  EXPECT_STREQ(r, "jar:");
+  free(r);
+
+  // Should not find a match
+  delim_begin = begin;
+  delim_end = end;
+  EXPECT_FALSE(RFindInReadable("gecko"_ns, delim_begin, delim_end));
+
+  // When no match is found, range should be empty
+  EXPECT_EQ(delim_begin, delim_end);
+
+  // Should not find a match (search not before Substring)
+  delim_begin = begin;
+  for (int i = 0; i < 6; i++) delim_begin++;
+  delim_end = end;
+  EXPECT_FALSE(RFindInReadable("jar:"_ns, delim_begin, delim_end));
+
+  // When no match is found, range should be empty
+  EXPECT_EQ(delim_begin, delim_end);
+
+  // Should not find a match (search not beyond Substring)
+  delim_begin = begin;
+  delim_end = end;
+  for (int i = 0; i < 7; i++) delim_end--;
+  EXPECT_FALSE(RFindInReadable("classic"_ns, delim_begin, delim_end));
+
+  // When no match is found, range should be empty
+  EXPECT_EQ(delim_begin, delim_end);
+}
+
+TEST_F(Strings, distance) {
+  const char text[] = "abc-xyz";
+  nsCString s(text);
+  nsCString::const_iterator begin, end;
+  s.BeginReading(begin);
+  s.EndReading(end);
+  size_t d = Distance(begin, end);
+  EXPECT_EQ(d, sizeof(text) - 1);
+}
+
+TEST_F(Strings, length) {
+  const char text[] = "abc-xyz";
+  nsCString s(text);
+  size_t d = s.Length();
+  EXPECT_EQ(d, sizeof(text) - 1);
+}
+
+TEST_F(Strings, trim) {
+  const char text[] = " a\t    $   ";
+  const char set[] = " \t$";
+
+  nsCString s(text);
+  s.Trim(set);
+  EXPECT_STREQ(s.get(), "a");
+
+  s.AssignLiteral("\t  \t\t  \t");
+  s.Trim(set);
+  EXPECT_STREQ(s.get(), "");
+
+  s.AssignLiteral(" ");
+  s.Trim(set);
+  EXPECT_STREQ(s.get(), "");
+
+  s.AssignLiteral(" ");
+  s.Trim(set, false, true);
+  EXPECT_STREQ(s.get(), "");
+
+  s.AssignLiteral(" ");
+  s.Trim(set, true, false);
+  EXPECT_STREQ(s.get(), "");
+}
+
+TEST_F(Strings, replace_substr) {
+  const char text[] = "abc-ppp-qqq-ppp-xyz";
+  nsCString s(text);
+  s.ReplaceSubstring("ppp", "www");
+  EXPECT_STREQ(s.get(), "abc-www-qqq-www-xyz");
+
+  s.AssignLiteral("foobar");
+  s.ReplaceSubstring("foo", "bar");
+  s.ReplaceSubstring("bar", "");
+  EXPECT_STREQ(s.get(), "");
+
+  s.AssignLiteral("foofoofoo");
+  s.ReplaceSubstring("foo", "foo");
+  EXPECT_STREQ(s.get(), "foofoofoo");
+
+  s.AssignLiteral("foofoofoo");
+  s.ReplaceSubstring("of", "fo");
+  EXPECT_STREQ(s.get(), "fofoofooo");
+}
+
+TEST_F(Strings, replace_substr_2) {
+  const char* newName = "user";
+  nsString acctName;
+  acctName.AssignLiteral("forums.foo.com");
+  nsAutoString newAcctName, oldVal, newVal;
+  CopyASCIItoUTF16(mozilla::MakeStringSpan(newName), newVal);
+  newAcctName.Assign(acctName);
+
+  // here, oldVal is empty.  we are testing that this function
+  // does not hang.  see bug 235355.
+  newAcctName.ReplaceSubstring(oldVal, newVal);
+
+  // we expect that newAcctName will be unchanged.
+  EXPECT_TRUE(newAcctName.Equals(acctName));
+}
+
+TEST_F(Strings, replace_substr_3) {
+  nsCString s;
+  s.AssignLiteral("abcabcabc");
+  s.ReplaceSubstring("ca", "X");
+  EXPECT_STREQ(s.get(), "abXbXbc");
+
+  s.AssignLiteral("abcabcabc");
+  s.ReplaceSubstring("ca", "XYZ");
+  EXPECT_STREQ(s.get(), "abXYZbXYZbc");
+
+  s.AssignLiteral("abcabcabc");
+  s.ReplaceSubstring("ca", "XY");
+  EXPECT_STREQ(s.get(), "abXYbXYbc");
+
+  s.AssignLiteral("abcabcabc");
+  s.ReplaceSubstring("ca", "XYZ!");
+  EXPECT_STREQ(s.get(), "abXYZ!bXYZ!bc");
+
+  s.AssignLiteral("abcdabcdabcd");
+  s.ReplaceSubstring("bcd", "X");
+  EXPECT_STREQ(s.get(), "aXaXaX");
+
+  s.AssignLiteral("abcdabcdabcd");
+  s.ReplaceSubstring("bcd", "XYZ!");
+  EXPECT_STREQ(s.get(), "aXYZ!aXYZ!aXYZ!");
+
+  s.AssignLiteral("abcdabcdabcd");
+  s.ReplaceSubstring("bcd", "XY");
+  EXPECT_STREQ(s.get(), "aXYaXYaXY");
+
+  s.AssignLiteral("abcdabcdabcd");
+  s.ReplaceSubstring("bcd", "XYZABC");
+  EXPECT_STREQ(s.get(), "aXYZABCaXYZABCaXYZABC");
+
+  s.AssignLiteral("abcdabcdabcd");
+  s.ReplaceSubstring("bcd", "XYZ");
+  EXPECT_STREQ(s.get(), "aXYZaXYZaXYZ");
+
+  s.AssignLiteral("abcdabcdabcd");
+  s.ReplaceSubstring("bcd", "XYZ!");
+  EXPECT_STREQ(s.get(), "aXYZ!aXYZ!aXYZ!");
+
+  s.AssignLiteral("abcdabcdabcd");
+  s.ReplaceSubstring("ab", "X");
+  EXPECT_STREQ(s.get(), "XcdXcdXcd");
+
+  s.AssignLiteral("abcdabcdabcd");
+  s.ReplaceSubstring("ab", "XYZABC");
+  EXPECT_STREQ(s.get(), "XYZABCcdXYZABCcdXYZABCcd");
+
+  s.AssignLiteral("abcdabcdabcd");
+  s.ReplaceSubstring("ab", "XY");
+  EXPECT_STREQ(s.get(), "XYcdXYcdXYcd");
+
+  s.AssignLiteral("abcdabcdabcd");
+  s.ReplaceSubstring("ab", "XYZ!");
+  EXPECT_STREQ(s.get(), "XYZ!cdXYZ!cdXYZ!cd");
+
+  s.AssignLiteral("abcdabcdabcd");
+  s.ReplaceSubstring("notfound", "X");
+  EXPECT_STREQ(s.get(), "abcdabcdabcd");
+
+  s.AssignLiteral("abcdabcdabcd");
+  s.ReplaceSubstring("notfound", "longlongstring");
+  EXPECT_STREQ(s.get(), "abcdabcdabcd");
+}
+
+TEST_F(Strings, strip_ws) {
+  const char* texts[] = {"", " a    $   ", "Some\fother\t thing\r\n",
+                         "And   \f\t\r\n even\nmore\r \f"};
+  const char* results[] = {"", "a$", "Someotherthing", "Andevenmore"};
+  for (size_t i = 0; i < sizeof(texts) / sizeof(texts[0]); i++) {
+    nsCString s(texts[i]);
+    s.StripWhitespace();
+    EXPECT_STREQ(s.get(), results[i]);
+  }
+}
+
+TEST_F(Strings, equals_ic) {
+  nsCString s;
+  EXPECT_FALSE(s.LowerCaseEqualsLiteral("view-source"));
+}
+
+TEST_F(Strings, concat) {
+  nsCString bar("bar");
+  const nsACString& barRef = bar;
+
+  const nsPromiseFlatCString& result =
+      PromiseFlatCString("foo"_ns + ","_ns + barRef);
+  EXPECT_STREQ(result.get(), "foo,bar");
+}
+
+TEST_F(Strings, concat_2) {
+  nsCString fieldTextStr("xyz");
+  nsCString text("text");
+  const nsACString& aText = text;
+
+  nsAutoCString result(fieldTextStr + aText);
+
+  EXPECT_STREQ(result.get(), "xyztext");
+}
+
+TEST_F(Strings, concat_3) {
+  nsCString result;
+  nsCString ab("ab"), c("c");
+
+  result = ab + result + c;
+  EXPECT_STREQ(result.get(), "abc");
+}
+
+TEST_F(Strings, empty_assign) {
+  nsCString a;
+  a.AssignLiteral("");
+
+  a.AppendLiteral("");
+
+  nsCString b;
+  b.SetCapacity(0);
+}
+
+TEST_F(Strings, set_length) {
+  const char kText[] = "Default Plugin";
+  nsCString buf;
+  buf.SetCapacity(sizeof(kText) - 1);
+  buf.Assign(kText);
+  buf.SetLength(sizeof(kText) - 1);
+  EXPECT_STREQ(buf.get(), kText);
+}
+
+TEST_F(Strings, substring) {
+  nsCString super("hello world"), sub("hello");
+
+  // this tests that |super| starts with |sub|,
+
+  EXPECT_TRUE(sub.Equals(StringHead(super, sub.Length())));
+
+  // and verifies that |sub| does not start with |super|.
+
+  EXPECT_FALSE(super.Equals(StringHead(sub, super.Length())));
+}
+
+#define test_append_expect(str, int, suffix, expect) \
+  str.Truncate();                                    \
+  str.AppendInt(suffix = int);                       \
+  EXPECT_TRUE(str.EqualsLiteral(expect));
+
+#define test_appends_expect(int, suffix, expect) \
+  test_append_expect(str, int, suffix, expect)   \
+      test_append_expect(cstr, int, suffix, expect)
+
+#define test_appendbase(str, prefix, int, suffix, base) \
+  str.Truncate();                                       \
+  str.AppendInt(suffix = prefix##int##suffix, base);    \
+  EXPECT_TRUE(str.EqualsLiteral(#int));
+
+#define test_appendbases(prefix, int, suffix, base) \
+  test_appendbase(str, prefix, int, suffix, base)   \
+      test_appendbase(cstr, prefix, int, suffix, base)
+
+TEST_F(Strings, appendint) {
+  nsString str;
+  nsCString cstr;
+  int32_t L;
+  uint32_t UL;
+  int64_t LL;
+  uint64_t ULL;
+  test_appends_expect(INT32_MAX, L, "2147483647");
+  test_appends_expect(INT32_MIN, L, "-2147483648");
+  test_appends_expect(UINT32_MAX, UL, "4294967295");
+  test_appends_expect(INT64_MAX, LL, "9223372036854775807");
+  test_appends_expect(INT64_MIN, LL, "-9223372036854775808");
+  test_appends_expect(UINT64_MAX, ULL, "18446744073709551615");
+  test_appendbases(0, 17777777777, L, 8);
+  test_appendbases(0, 20000000000, L, 8);
+  test_appendbases(0, 37777777777, UL, 8);
+  test_appendbases(0, 777777777777777777777, LL, 8);
+  test_appendbases(0, 1000000000000000000000, LL, 8);
+  test_appendbases(0, 1777777777777777777777, ULL, 8);
+  test_appendbases(0x, 7fffffff, L, 16);
+  test_appendbases(0x, 80000000, L, 16);
+  test_appendbases(0x, ffffffff, UL, 16);
+  test_appendbases(0x, 7fffffffffffffff, LL, 16);
+  test_appendbases(0x, 8000000000000000, LL, 16);
+  test_appendbases(0x, ffffffffffffffff, ULL, 16);
+}
+
+TEST_F(Strings, appendint64) {
+  nsCString str;
+
+  int64_t max = INT64_MAX;
+  static const char max_expected[] = "9223372036854775807";
+  int64_t min = INT64_MIN;
+  static const char min_expected[] = "-9223372036854775808";
+  static const char min_expected_oct[] = "1000000000000000000000";
+  int64_t maxint_plus1 = 1LL << 32;
+  static const char maxint_plus1_expected[] = "4294967296";
+  static const char maxint_plus1_expected_x[] = "100000000";
+
+  str.AppendInt(max);
+
+  EXPECT_TRUE(str.Equals(max_expected));
+
+  str.Truncate();
+  str.AppendInt(min);
+  EXPECT_TRUE(str.Equals(min_expected));
+  str.Truncate();
+  str.AppendInt(min, 8);
+  EXPECT_TRUE(str.Equals(min_expected_oct));
+
+  str.Truncate();
+  str.AppendInt(maxint_plus1);
+  EXPECT_TRUE(str.Equals(maxint_plus1_expected));
+  str.Truncate();
+  str.AppendInt(maxint_plus1, 16);
+  EXPECT_TRUE(str.Equals(maxint_plus1_expected_x));
+}
+
+TEST_F(Strings, inttotstring) {
+  EXPECT_EQ("42"_ns, IntToCString(42));
+  EXPECT_EQ(u"42"_ns, IntToString(42));
+
+  EXPECT_EQ("2a"_ns, IntToCString(42, 16));
+  EXPECT_EQ(u"2a"_ns, IntToString(42, 16));
+}
+
+TEST_F(Strings, appendfloat) {
+  nsCString str;
+  double bigdouble = 11223344556.66;
+  static const char double_expected[] = "11223344556.66";
+  static const char float_expected[] = "0.01";
+
+  // AppendFloat is used to append doubles, therefore the precision must be
+  // large enough (see bug 327719)
+  str.AppendFloat(bigdouble);
+  EXPECT_TRUE(str.Equals(double_expected));
+
+  str.Truncate();
+  // AppendFloat is used to append floats (bug 327719 #27)
+  str.AppendFloat(0.1f * 0.1f);
+  EXPECT_TRUE(str.Equals(float_expected));
+}
+
+TEST_F(Strings, findcharinset) {
+  nsCString buf("hello, how are you?");
+
+  int32_t index = buf.FindCharInSet(",?", 5);
+  EXPECT_EQ(index, 5);
+
+  index = buf.FindCharInSet("helo", 0);
+  EXPECT_EQ(index, 0);
+
+  index = buf.FindCharInSet("z?", 6);
+  EXPECT_EQ(index, (int32_t)buf.Length() - 1);
+}
+
+TEST_F(Strings, rfindcharinset) {
+  nsCString buf("hello, how are you?");
+
+  int32_t index = buf.RFindCharInSet(",?", 5);
+  EXPECT_EQ(index, 5);
+
+  index = buf.RFindCharInSet("helo", 0);
+  EXPECT_EQ(index, 0);
+
+  index = buf.RFindCharInSet("z?", 6);
+  EXPECT_EQ(index, kNotFound);
+
+  index = buf.RFindCharInSet("l", 5);
+  EXPECT_EQ(index, 3);
+
+  buf.AssignLiteral("abcdefghijkabc");
+
+  index = buf.RFindCharInSet("ab");
+  EXPECT_EQ(index, 12);
+
+  index = buf.RFindCharInSet("ab", 11);
+  EXPECT_EQ(index, 11);
+
+  index = buf.RFindCharInSet("ab", 10);
+  EXPECT_EQ(index, 1);
+
+  index = buf.RFindCharInSet("ab", 0);
+  EXPECT_EQ(index, 0);
+
+  index = buf.RFindCharInSet("cd", 1);
+  EXPECT_EQ(index, kNotFound);
+
+  index = buf.RFindCharInSet("h");
+  EXPECT_EQ(index, 7);
+}
+
+TEST_F(Strings, stringbuffer) {
+  const char kData[] = "hello world";
+
+  RefPtr<nsStringBuffer> buf;
+
+  buf = nsStringBuffer::Alloc(sizeof(kData));
+  EXPECT_TRUE(!!buf);
+
+  buf = nsStringBuffer::Alloc(sizeof(kData));
+  EXPECT_TRUE(!!buf);
+  char* data = (char*)buf->Data();
+  memcpy(data, kData, sizeof(kData));
+
+  nsCString str;
+  buf->ToString(sizeof(kData) - 1, str);
+
+  nsStringBuffer* buf2;
+  buf2 = nsStringBuffer::FromString(str);
+
+  EXPECT_EQ(buf, buf2);
+}
+
+TEST_F(Strings, voided) {
+  const char kData[] = "hello world";
+
+  nsCString str;
+  EXPECT_TRUE(!str.IsVoid());
+  EXPECT_TRUE(str.IsEmpty());
+  EXPECT_STREQ(str.get(), "");
+
+  str.SetIsVoid(true);
+  EXPECT_TRUE(str.IsVoid());
+  EXPECT_TRUE(str.IsEmpty());
+  EXPECT_STREQ(str.get(), "");
+
+  str.Assign(kData);
+  EXPECT_TRUE(!str.IsVoid());
+  EXPECT_TRUE(!str.IsEmpty());
+  EXPECT_STREQ(str.get(), kData);
+
+  str.SetIsVoid(true);
+  EXPECT_TRUE(str.IsVoid());
+  EXPECT_TRUE(str.IsEmpty());
+  EXPECT_STREQ(str.get(), "");
+
+  str.SetIsVoid(false);
+  EXPECT_TRUE(!str.IsVoid());
+  EXPECT_TRUE(str.IsEmpty());
+  EXPECT_STREQ(str.get(), "");
+
+  str.Assign(kData);
+  EXPECT_TRUE(!str.IsVoid());
+  EXPECT_TRUE(!str.IsEmpty());
+  EXPECT_STREQ(str.get(), kData);
+
+  str.Adopt(nullptr);
+  EXPECT_TRUE(str.IsVoid());
+  EXPECT_TRUE(str.IsEmpty());
+  EXPECT_STREQ(str.get(), "");
+}
+
+TEST_F(Strings, voided_autostr) {
+  const char kData[] = "hello world";
+
+  nsAutoCString str;
+  EXPECT_FALSE(str.IsVoid());
+  EXPECT_TRUE(str.IsEmpty());
+
+  str.Assign(kData);
+  EXPECT_STREQ(str.get(), kData);
+
+  str.SetIsVoid(true);
+  EXPECT_TRUE(str.IsVoid());
+  EXPECT_TRUE(str.IsEmpty());
+
+  str.Assign(kData);
+  EXPECT_FALSE(str.IsVoid());
+  EXPECT_FALSE(str.IsEmpty());
+  EXPECT_STREQ(str.get(), kData);
+}
+
+TEST_F(Strings, voided_assignment) {
+  nsCString a, b;
+  b.SetIsVoid(true);
+  a = b;
+  EXPECT_TRUE(a.IsVoid());
+  EXPECT_EQ(a.get(), b.get());
+}
+
+TEST_F(Strings, empty_assignment) {
+  nsCString a, b;
+  a = b;
+  EXPECT_EQ(a.get(), b.get());
+}
+
+struct ToIntegerTest {
+  const char* str;
+  uint32_t radix;
+  int32_t result;
+  nsresult rv;
+};
+
+static const ToIntegerTest kToIntegerTests[] = {
+    {"123", 10, 123, NS_OK},
+    {"7b", 16, 123, NS_OK},
+    {"90194313659", 10, 0, NS_ERROR_ILLEGAL_VALUE},
+    {nullptr, 0, 0, NS_OK}};
+
+TEST_F(Strings, string_tointeger) {
+  nsresult rv;
+  for (const ToIntegerTest* t = kToIntegerTests; t->str; ++t) {
+    int32_t result = nsAutoCString(t->str).ToInteger(&rv, t->radix);
+    EXPECT_EQ(rv, t->rv);
+    EXPECT_EQ(result, t->result);
+    result = nsAutoCString(t->str).ToInteger(&rv, t->radix);
+    EXPECT_EQ(rv, t->rv);
+    EXPECT_EQ(result, t->result);
+  }
+}
+
+static void test_parse_string_helper(const char* str, char separator, int len,
+                                     const char* s1, const char* s2) {
+  nsCString data(str);
+  nsTArray<nsCString> results;
+  ParseString(data, separator, results);
+  EXPECT_EQ(int(results.Length()), len);
+  const char* strings[] = {s1, s2};
+  for (int i = 0; i < len; ++i) {
+    EXPECT_TRUE(results[i].Equals(strings[i]));
+  }
+}
+
+static void test_parse_string_helper0(const char* str, char separator) {
+  test_parse_string_helper(str, separator, 0, nullptr, nullptr);
+}
+
+static void test_parse_string_helper1(const char* str, char separator,
+                                      const char* s1) {
+  test_parse_string_helper(str, separator, 1, s1, nullptr);
+}
+
+static void test_parse_string_helper2(const char* str, char separator,
+                                      const char* s1, const char* s2) {
+  test_parse_string_helper(str, separator, 2, s1, s2);
+}
+
+TEST(String, parse_string)
+{
+  test_parse_string_helper1("foo, bar", '_', "foo, bar");
+  test_parse_string_helper2("foo, bar", ',', "foo", " bar");
+  test_parse_string_helper2("foo, bar ", ' ', "foo,", "bar");
+  test_parse_string_helper2("foo,bar", 'o', "f", ",bar");
+  test_parse_string_helper0("", '_');
+  test_parse_string_helper0("  ", ' ');
+  test_parse_string_helper1(" foo", ' ', "foo");
+  test_parse_string_helper1("  foo", ' ', "foo");
+}
+
+static void test_strip_chars_helper(const char16_t* str, const char16_t* strip,
+                                    const nsAString& result) {
+  nsAutoString data(str);
+  data.StripChars(strip);
+  EXPECT_TRUE(data.Equals(result));
+}
+
+TEST(String, strip_chars)
+{
+  test_strip_chars_helper(u"foo \r \nbar", u" \n\r", u"foobar"_ns);
+  test_strip_chars_helper(u"\r\nfoo\r\n", u" \n\r", u"foo"_ns);
+  test_strip_chars_helper(u"foo", u" \n\r", u"foo"_ns);
+  test_strip_chars_helper(u"foo", u"fo", u""_ns);
+  test_strip_chars_helper(u"foo", u"foo", u""_ns);
+  test_strip_chars_helper(u" foo", u" ", u"foo"_ns);
+}
+
+TEST_F(Strings, append_with_capacity) {
+  nsAutoString s;
+  const char16_t* origPtr = s.BeginReading();
+  s.SetCapacity(8000);
+  const char16_t* ptr = s.BeginReading();
+  EXPECT_NE(origPtr, ptr);
+  for (int i = 0; i < 100; i++) {
+    s.Append(u'a');
+    EXPECT_EQ(s.BeginReading(), ptr);
+    EXPECT_EQ(s.Length(), uint32_t(i + 1));
+  }
+}
+
+TEST_F(Strings, append_string_with_capacity) {
+  nsAutoString aa;
+  aa.Append(u'a');
+  aa.Append(u'a');
+  nsAutoString s;
+  const char16_t* origPtr = s.BeginReading();
+  s.SetCapacity(8000);
+  const char16_t* ptr = s.BeginReading();
+  EXPECT_NE(origPtr, ptr);
+  nsAutoString empty;
+  s.Append(empty);
+  EXPECT_EQ(s.BeginReading(), ptr);
+  for (int i = 0; i < 100; i++) {
+    s.Append(aa);
+    EXPECT_EQ(s.BeginReading(), ptr);
+    EXPECT_EQ(s.Length(), uint32_t(2 * (i + 1)));
+  }
+}
+
+TEST_F(Strings, append_literal_with_capacity) {
+  nsAutoString s;
+  const char16_t* origPtr = s.BeginReading();
+  s.SetCapacity(8000);
+  const char16_t* ptr = s.BeginReading();
+  EXPECT_NE(origPtr, ptr);
+  s.AppendLiteral(u"");
+  EXPECT_EQ(s.BeginReading(), ptr);
+  for (int i = 0; i < 100; i++) {
+    s.AppendLiteral(u"aa");
+    EXPECT_EQ(s.BeginReading(), ptr);
+    EXPECT_EQ(s.Length(), uint32_t(2 * (i + 1)));
+  }
+}
+
+// The following test is intentionally not memory
+// checking-clean.
+#if !(defined(MOZ_HAVE_MEM_CHECKS) || defined(MOZ_MSAN))
+TEST_F(Strings, legacy_set_length_semantics) {
+  const char* foobar = "foobar";
+  nsCString s;
+  s.SetCapacity(2048);
+  memcpy(s.BeginWriting(), foobar, strlen(foobar));
+  s.SetLength(strlen(foobar));
+  EXPECT_FALSE(s.EqualsASCII(foobar));
+}
+#endif
+
+TEST_F(Strings, bulk_write) {
+  nsCString s;
+  const char* ptrTwoThousand;
+  {
+    auto handleOrErr = s.BulkWrite(500, 0, true);
+    EXPECT_TRUE(handleOrErr.isOk());
+
+    auto handle = handleOrErr.unwrap();
+
+    auto span = handle.AsSpan();
+    for (auto&& c : span) {
+      c = 'a';
+    }
+    mozilla::Unused << handle.RestartBulkWrite(2000, 500, false);
+    span = handle.AsSpan().From(500);
+    for (auto&& c : span) {
+      c = 'b';
+    }
+    ptrTwoThousand = handle.Elements();
+    handle.Finish(1000, true);
+  }
+  EXPECT_EQ(s.Length(), 1000U);
+  EXPECT_NE(s.BeginReading(), ptrTwoThousand);
+  EXPECT_EQ(s.BeginReading()[1000], '\0');
+  for (uint32_t i = 0; i < 500; i++) {
+    EXPECT_EQ(s[i], 'a');
+  }
+  for (uint32_t i = 500; i < 1000; i++) {
+    EXPECT_EQ(s[i], 'b');
+  }
+}
+
+TEST_F(Strings, bulk_write_fail) {
+  nsCString s;
+  {
+    auto handleOrErr = s.BulkWrite(500, 0, true);
+    EXPECT_TRUE(handleOrErr.isOk());
+  }
+  EXPECT_EQ(s.Length(), 3U);
+  EXPECT_TRUE(s.Equals(u8"\uFFFD"));
+}
+
+TEST_F(Strings, huge_capacity) {
+  nsString a, b, c, d, e, f, g, h, i, j, k, l, m, n, o;
+  nsCString n1, o1;
+
+  // Ignore the result if the address space is less than 64-bit because
+  // some of the allocations above will exhaust the address space.
+  if (sizeof(void*) >= 8) {
+    EXPECT_TRUE(a.SetCapacity(1, fallible));
+    EXPECT_FALSE(a.SetCapacity(uint32_t(-1) / 2, fallible));
+    a.Truncate();  // free the allocated memory
+
+    EXPECT_TRUE(b.SetCapacity(1, fallible));
+    EXPECT_FALSE(b.SetCapacity(uint32_t(-1) / 2 - 1, fallible));
+    b.Truncate();
+
+    EXPECT_TRUE(c.SetCapacity(1, fallible));
+    EXPECT_FALSE(c.SetCapacity(uint32_t(-1) / 2, fallible));
+    c.Truncate();
+
+    EXPECT_FALSE(d.SetCapacity(uint32_t(-1) / 2 - 1, fallible));
+    EXPECT_FALSE(d.SetCapacity(uint32_t(-1) / 2, fallible));
+    d.Truncate();
+
+    EXPECT_FALSE(e.SetCapacity(uint32_t(-1) / 4, fallible));
+    EXPECT_FALSE(e.SetCapacity(uint32_t(-1) / 4 + 1, fallible));
+    e.Truncate();
+
+    EXPECT_FALSE(f.SetCapacity(uint32_t(-1) / 2, fallible));
+    f.Truncate();
+
+    EXPECT_FALSE(g.SetCapacity(uint32_t(-1) / 4 + 1000, fallible));
+    EXPECT_FALSE(g.SetCapacity(uint32_t(-1) / 4 + 1001, fallible));
+    g.Truncate();
+
+    EXPECT_FALSE(h.SetCapacity(uint32_t(-1) / 4 + 1, fallible));
+    EXPECT_FALSE(h.SetCapacity(uint32_t(-1) / 2, fallible));
+    h.Truncate();
+
+    EXPECT_TRUE(i.SetCapacity(1, fallible));
+    EXPECT_TRUE(i.SetCapacity(uint32_t(-1) / 4 - 1000, fallible));
+    EXPECT_FALSE(i.SetCapacity(uint32_t(-1) / 4 + 1, fallible));
+    i.Truncate();
+
+    EXPECT_TRUE(j.SetCapacity(uint32_t(-1) / 4 - 1000, fallible));
+    EXPECT_FALSE(j.SetCapacity(uint32_t(-1) / 4 + 1, fallible));
+    j.Truncate();
+
+// Disabled due to intermittent failures.
+// https://bugzilla.mozilla.org/show_bug.cgi?id=1493458
+#if 0
+    EXPECT_TRUE(k.SetCapacity(uint32_t(-1)/8 - 1000, fallible));
+    EXPECT_TRUE(k.SetCapacity(uint32_t(-1)/4 - 1001, fallible));
+    EXPECT_TRUE(k.SetCapacity(uint32_t(-1)/4 - 998, fallible));
+    EXPECT_FALSE(k.SetCapacity(uint32_t(-1)/4 + 1, fallible));
+    k.Truncate();
+#endif
+
+    EXPECT_TRUE(l.SetCapacity(uint32_t(-1) / 8, fallible));
+    EXPECT_TRUE(l.SetCapacity(uint32_t(-1) / 8 + 1, fallible));
+    EXPECT_TRUE(l.SetCapacity(uint32_t(-1) / 8 + 2, fallible));
+    l.Truncate();
+
+    EXPECT_TRUE(m.SetCapacity(uint32_t(-1) / 8 + 1000, fallible));
+    EXPECT_TRUE(m.SetCapacity(uint32_t(-1) / 8 + 1001, fallible));
+    m.Truncate();
+
+    EXPECT_TRUE(n.SetCapacity(uint32_t(-1) / 8 + 1, fallible));
+    EXPECT_FALSE(n.SetCapacity(uint32_t(-1) / 4, fallible));
+    n.Truncate();
+
+    n.Truncate();
+    EXPECT_TRUE(n.SetCapacity((uint32_t(-1) / 2) / 2 - 1, fallible));
+    n.Truncate();
+    EXPECT_FALSE(n.SetCapacity((uint32_t(-1) / 2) / 2, fallible));
+    n.Truncate();
+    n1.Truncate();
+    EXPECT_TRUE(n1.SetCapacity((uint32_t(-1) / 2) / 1 - 1, fallible));
+    n1.Truncate();
+    EXPECT_FALSE(n1.SetCapacity((uint32_t(-1) / 2) / 1, fallible));
+    n1.Truncate();
+
+    // The longest possible JS string should fit within both a `nsString` and
+    // nsCString.
+    EXPECT_TRUE(o.SetCapacity(JS::MaxStringLength, fallible));
+    o.Truncate();
+    EXPECT_TRUE(o1.SetCapacity(JS::MaxStringLength, fallible));
+    o1.Truncate();
+  }
+}
+
+static void test_tofloat_helper(const nsString& aStr,
+                                mozilla::Maybe<float> aExpected) {
+  nsresult result;
+  float value = aStr.ToFloat(&result);
+  if (aExpected) {
+    EXPECT_TRUE(NS_SUCCEEDED(result));
+    EXPECT_EQ(value, *aExpected);
+  } else {
+    EXPECT_TRUE(NS_FAILED(result));
+  }
+}
+
+TEST_F(Strings, tofloat) {
+  test_tofloat_helper(u"42"_ns, Some(42.f));
+  test_tofloat_helper(u"42.0"_ns, Some(42.f));
+  test_tofloat_helper(u"-42"_ns, Some(-42.f));
+  test_tofloat_helper(u"+42"_ns, Some(42));
+  test_tofloat_helper(u"13.37"_ns, Some(13.37f));
+  test_tofloat_helper(u"1.23456789"_ns, Some(1.23456789f));
+  test_tofloat_helper(u"1.98765432123456"_ns, Some(1.98765432123456f));
+  test_tofloat_helper(u"0"_ns, Some(0.f));
+  test_tofloat_helper(u"1.e5"_ns, Some(100000));
+  test_tofloat_helper(u""_ns, Nothing());
+  test_tofloat_helper(u"42foo"_ns, Nothing());
+  test_tofloat_helper(u"foo"_ns, Nothing());
+  test_tofloat_helper(u"1.5e-"_ns, Nothing());
+
+  // Leading spaces are ignored
+  test_tofloat_helper(u"  \t5"_ns, Some(5.f));
+
+  // Values which are too large generate an error
+  test_tofloat_helper(u"3.402823e38"_ns, Some(3.402823e+38));
+  test_tofloat_helper(u"1e39"_ns, Nothing());
+  test_tofloat_helper(u"-3.402823e38"_ns, Some(-3.402823e+38));
+  test_tofloat_helper(u"-1e39"_ns, Nothing());
+
+  // Values which are too small round to zero
+  test_tofloat_helper(u"1.4013e-45"_ns, Some(1.4013e-45f));
+  test_tofloat_helper(u"1e-46"_ns, Some(0.f));
+  test_tofloat_helper(u"-1.4013e-45"_ns, Some(-1.4013e-45f));
+  test_tofloat_helper(u"-1e-46"_ns, Some(-0.f));
+}
+
+static void test_tofloat_allow_trailing_chars_helper(const nsString& aStr,
+                                                     Maybe<float> aExpected) {
+  nsresult result;
+  float value = aStr.ToFloatAllowTrailingChars(&result);
+  if (aExpected) {
+    EXPECT_TRUE(NS_SUCCEEDED(result));
+    EXPECT_EQ(value, *aExpected);
+  } else {
+    EXPECT_TRUE(NS_FAILED(result));
+  }
+}
+
+TEST_F(Strings, ToFloatAllowTrailingChars) {
+  test_tofloat_allow_trailing_chars_helper(u""_ns, Nothing());
+  test_tofloat_allow_trailing_chars_helper(u"foo"_ns, Nothing());
+  test_tofloat_allow_trailing_chars_helper(u"42foo"_ns, Some(42.f));
+  test_tofloat_allow_trailing_chars_helper(u"42-5"_ns, Some(42.f));
+  test_tofloat_allow_trailing_chars_helper(u"13.37.8"_ns, Some(13.37f));
+  test_tofloat_allow_trailing_chars_helper(u"1.5e-"_ns, Some(1.5f));
+}
+
+static void test_todouble_helper(const nsString& aStr,
+                                 Maybe<double> aExpected) {
+  nsresult result;
+  double value = aStr.ToDouble(&result);
+  if (aExpected) {
+    EXPECT_TRUE(NS_SUCCEEDED(result));
+    EXPECT_EQ(value, *aExpected);
+  } else {
+    EXPECT_TRUE(NS_FAILED(result));
+  }
+}
+
+TEST_F(Strings, todouble) {
+  test_todouble_helper(u"42"_ns, Some(42));
+  test_todouble_helper(u"42.0"_ns, Some(42));
+  test_todouble_helper(u"-42"_ns, Some(-42));
+  test_todouble_helper(u"+42"_ns, Some(42));
+  test_todouble_helper(u"13.37"_ns, Some(13.37));
+  test_todouble_helper(u"1.23456789"_ns, Some(1.23456789));
+  test_todouble_helper(u"1.98765432123456"_ns, Some(1.98765432123456));
+  test_todouble_helper(u"123456789.98765432123456"_ns,
+                       Some(123456789.98765432123456));
+  test_todouble_helper(u"0"_ns, Some(0));
+  test_todouble_helper(u"1.e5"_ns, Some(100000));
+  test_todouble_helper(u""_ns, Nothing());
+  test_todouble_helper(u"42foo"_ns, Nothing());
+  test_todouble_helper(u"foo"_ns, Nothing());
+  test_todouble_helper(u"1.5e-"_ns, Nothing());
+
+  // Leading spaces are ignored
+  test_todouble_helper(u"  \t5"_ns, Some(5.));
+
+  // Values which are too large generate an error
+  test_todouble_helper(u"1.797693e+308"_ns, Some(1.797693e+308));
+  test_todouble_helper(u"1e309"_ns, Nothing());
+  test_todouble_helper(u"-1.797693e+308"_ns, Some(-1.797693e+308));
+  test_todouble_helper(u"-1e309"_ns, Nothing());
+
+  // Values which are too small round to zero
+  test_todouble_helper(u"4.940656e-324"_ns, Some(4.940656e-324));
+  test_todouble_helper(u"1e-325"_ns, Some(0.));
+  test_todouble_helper(u"-4.940656e-324"_ns, Some(-4.940656e-324));
+  test_todouble_helper(u"-1e-325"_ns, Some(-0.));
+}
+
+static void test_todouble_allow_trailing_chars_helper(const nsString& aStr,
+                                                      Maybe<double> aExpected) {
+  nsresult result;
+  double value = aStr.ToDoubleAllowTrailingChars(&result);
+  if (aExpected) {
+    EXPECT_TRUE(NS_SUCCEEDED(result));
+    EXPECT_EQ(value, *aExpected);
+  } else {
+    EXPECT_TRUE(NS_FAILED(result));
+  }
+}
+
+TEST_F(Strings, ToDoubleAllowTrailingChars) {
+  test_todouble_allow_trailing_chars_helper(u""_ns, Nothing());
+  test_todouble_allow_trailing_chars_helper(u"foo"_ns, Nothing());
+  test_todouble_allow_trailing_chars_helper(u"42foo"_ns, Some(42));
+  test_todouble_allow_trailing_chars_helper(u"42-5"_ns, Some(42));
+  test_todouble_allow_trailing_chars_helper(u"13.37.8"_ns, Some(13.37));
+  test_todouble_allow_trailing_chars_helper(u"1.5e-"_ns, Some(1.5));
+}
+
+TEST_F(Strings, Split) {
+  nsCString one("one"), two("one;two"), three("one--three"), empty(""),
+      delimStart("-two"), delimEnd("one-");
+
+  nsString wide(u"hello world");
+
+  size_t counter = 0;
+  for (const nsACString& token : one.Split(',')) {
+    EXPECT_TRUE(token.EqualsLiteral("one"));
+    counter++;
+  }
+  EXPECT_EQ(counter, (size_t)1);
+
+  counter = 0;
+  for (const nsACString& token : two.Split(';')) {
+    if (counter == 0) {
+      EXPECT_TRUE(token.EqualsLiteral("one"));
+    } else if (counter == 1) {
+      EXPECT_TRUE(token.EqualsLiteral("two"));
+    }
+    counter++;
+  }
+  EXPECT_EQ(counter, (size_t)2);
+
+  counter = 0;
+  for (const nsACString& token : three.Split('-')) {
+    if (counter == 0) {
+      EXPECT_TRUE(token.EqualsLiteral("one"));
+    } else if (counter == 1) {
+      EXPECT_TRUE(token.EqualsLiteral(""));
+    } else if (counter == 2) {
+      EXPECT_TRUE(token.EqualsLiteral("three"));
+    }
+    counter++;
+  }
+  EXPECT_EQ(counter, (size_t)3);
+
+  counter = 0;
+  for (const nsACString& token : empty.Split(',')) {
+    mozilla::Unused << token;
+    counter++;
+  }
+  EXPECT_EQ(counter, (size_t)0);
+
+  counter = 0;
+  for (const nsACString& token : delimStart.Split('-')) {
+    if (counter == 0) {
+      EXPECT_TRUE(token.EqualsLiteral(""));
+    } else if (counter == 1) {
+      EXPECT_TRUE(token.EqualsLiteral("two"));
+    }
+    counter++;
+  }
+  EXPECT_EQ(counter, (size_t)2);
+
+  counter = 0;
+  for (const nsACString& token : delimEnd.Split('-')) {
+    if (counter == 0) {
+      EXPECT_TRUE(token.EqualsLiteral("one"));
+    } else if (counter == 1) {
+      EXPECT_TRUE(token.EqualsLiteral(""));
+    }
+    counter++;
+  }
+  EXPECT_EQ(counter, (size_t)2);
+
+  counter = 0;
+  for (const nsAString& token : wide.Split(' ')) {
+    if (counter == 0) {
+      EXPECT_TRUE(token.Equals(u"hello"_ns));
+    } else if (counter == 1) {
+      EXPECT_TRUE(token.Equals(u"world"_ns));
+    }
+    counter++;
+  }
+  EXPECT_EQ(counter, (size_t)2);
+}
+
+TEST_F(Strings, Join) {
+  // Join a sequence of strings.
+  {
+    // 8-bit strings
+    EXPECT_EQ(""_ns, StringJoin(","_ns, std::array<nsCString, 0>{}));
+    EXPECT_EQ("foo"_ns, StringJoin(","_ns, std::array{"foo"_ns}));
+    EXPECT_EQ("foo,bar"_ns, StringJoin(","_ns, std::array{"foo"_ns, "bar"_ns}));
+
+    // 16-bit strings
+    EXPECT_EQ(u""_ns, StringJoin(u","_ns, std::array<nsString, 0>{}));
+    EXPECT_EQ(u"foo"_ns, StringJoin(u","_ns, std::array{u"foo"_ns}));
+    EXPECT_EQ(u"foo,bar"_ns,
+              StringJoin(u","_ns, std::array{u"foo"_ns, u"bar"_ns}));
+  }
+
+  // Join a sequence of strings, appending.
+  {
+    // 8-bit string
+    {
+      nsAutoCString dst{"prefix:"_ns};
+      StringJoinAppend(dst, ","_ns, std::array{"foo"_ns, "bar"_ns});
+      EXPECT_EQ("prefix:foo,bar"_ns, dst);
+    }
+
+    // 16-bit string
+    {
+      nsAutoString dst{u"prefix:"_ns};
+      StringJoinAppend(dst, u","_ns, std::array{u"foo"_ns, u"bar"_ns});
+      EXPECT_EQ(u"prefix:foo,bar"_ns, dst);
+    }
+  }
+}
+
+TEST_F(Strings, JoinWithAppendingTransformation) {
+  const auto toCString = [](nsACString& dst, int val) { dst.AppendInt(val); };
+  const auto toString = [](nsAString& dst, int val) { dst.AppendInt(val); };
+
+  // Join a sequence of elements transformed to a string.
+  {
+    // 8-bit strings
+    EXPECT_EQ(""_ns, StringJoin(","_ns, std::array<int, 0>{}, toCString));
+    EXPECT_EQ("7"_ns, StringJoin(","_ns, std::array{7}, toCString));
+    EXPECT_EQ("7,42"_ns, StringJoin(","_ns, std::array{7, 42}, toCString));
+
+    // 16-bit strings
+    EXPECT_EQ(u""_ns, StringJoin(u","_ns, std::array<int, 0>{}, toString));
+    EXPECT_EQ(u"7"_ns, StringJoin(u","_ns, std::array{7}, toString));
+    EXPECT_EQ(u"7,42"_ns, StringJoin(u","_ns, std::array{7, 42}, toString));
+  }
+
+  // Join a sequence of elements transformed to a string, appending.
+  {
+    // 8-bit string
+    {
+      nsAutoCString dst{"prefix:"_ns};
+      StringJoinAppend(dst, ","_ns, std::array{7, 42}, toCString);
+      EXPECT_EQ("prefix:7,42"_ns, dst);
+    }
+
+    // 16-bit string
+    {
+      nsAutoString dst{u"prefix:"_ns};
+      StringJoinAppend(dst, u","_ns, std::array{7, 42}, toString);
+      EXPECT_EQ(u"prefix:7,42"_ns, dst);
+    }
+  }
+}
+
+constexpr bool TestSomeChars(char c) {
+  return c == 'a' || c == 'c' || c == 'e' || c == '7' || c == 'G' || c == 'Z' ||
+         c == '\b' || c == '?';
+}
+TEST_F(Strings, ASCIIMask) {
+  const ASCIIMaskArray& maskCRLF = mozilla::ASCIIMask::MaskCRLF();
+  EXPECT_TRUE(maskCRLF['\n'] && mozilla::ASCIIMask::IsMasked(maskCRLF, '\n'));
+  EXPECT_TRUE(maskCRLF['\r'] && mozilla::ASCIIMask::IsMasked(maskCRLF, '\r'));
+  EXPECT_FALSE(maskCRLF['g'] || mozilla::ASCIIMask::IsMasked(maskCRLF, 'g'));
+  EXPECT_FALSE(maskCRLF[' '] || mozilla::ASCIIMask::IsMasked(maskCRLF, ' '));
+  EXPECT_FALSE(maskCRLF['\0'] || mozilla::ASCIIMask::IsMasked(maskCRLF, '\0'));
+  EXPECT_FALSE(mozilla::ASCIIMask::IsMasked(maskCRLF, 14324));
+
+  const ASCIIMaskArray& mask0to9 = mozilla::ASCIIMask::Mask0to9();
+  EXPECT_TRUE(mask0to9['9'] && mozilla::ASCIIMask::IsMasked(mask0to9, '9'));
+  EXPECT_TRUE(mask0to9['0'] && mozilla::ASCIIMask::IsMasked(mask0to9, '0'));
+  EXPECT_TRUE(mask0to9['4'] && mozilla::ASCIIMask::IsMasked(mask0to9, '4'));
+  EXPECT_FALSE(mask0to9['g'] || mozilla::ASCIIMask::IsMasked(mask0to9, 'g'));
+  EXPECT_FALSE(mask0to9[' '] || mozilla::ASCIIMask::IsMasked(mask0to9, ' '));
+  EXPECT_FALSE(mask0to9['\n'] || mozilla::ASCIIMask::IsMasked(mask0to9, '\n'));
+  EXPECT_FALSE(mask0to9['\0'] || mozilla::ASCIIMask::IsMasked(mask0to9, '\0'));
+  EXPECT_FALSE(mozilla::ASCIIMask::IsMasked(maskCRLF, 14324));
+
+  const ASCIIMaskArray& maskWS = mozilla::ASCIIMask::MaskWhitespace();
+  EXPECT_TRUE(maskWS[' '] && mozilla::ASCIIMask::IsMasked(maskWS, ' '));
+  EXPECT_TRUE(maskWS['\t'] && mozilla::ASCIIMask::IsMasked(maskWS, '\t'));
+  EXPECT_FALSE(maskWS['8'] || mozilla::ASCIIMask::IsMasked(maskWS, '8'));
+  EXPECT_FALSE(maskWS['\0'] || mozilla::ASCIIMask::IsMasked(maskWS, '\0'));
+  EXPECT_FALSE(mozilla::ASCIIMask::IsMasked(maskCRLF, 14324));
+
+  constexpr ASCIIMaskArray maskSome = mozilla::CreateASCIIMask(TestSomeChars);
+  EXPECT_TRUE(maskSome['a'] && mozilla::ASCIIMask::IsMasked(maskSome, 'a'));
+  EXPECT_TRUE(maskSome['c'] && mozilla::ASCIIMask::IsMasked(maskSome, 'c'));
+  EXPECT_TRUE(maskSome['e'] && mozilla::ASCIIMask::IsMasked(maskSome, 'e'));
+  EXPECT_TRUE(maskSome['7'] && mozilla::ASCIIMask::IsMasked(maskSome, '7'));
+  EXPECT_TRUE(maskSome['G'] && mozilla::ASCIIMask::IsMasked(maskSome, 'G'));
+  EXPECT_TRUE(maskSome['Z'] && mozilla::ASCIIMask::IsMasked(maskSome, 'Z'));
+  EXPECT_TRUE(maskSome['\b'] && mozilla::ASCIIMask::IsMasked(maskSome, '\b'));
+  EXPECT_TRUE(maskSome['?'] && mozilla::ASCIIMask::IsMasked(maskSome, '?'));
+  EXPECT_FALSE(maskSome['8'] || mozilla::ASCIIMask::IsMasked(maskSome, '8'));
+  EXPECT_FALSE(maskSome['\0'] || mozilla::ASCIIMask::IsMasked(maskSome, '\0'));
+  EXPECT_FALSE(mozilla::ASCIIMask::IsMasked(maskCRLF, 14324));
+}
+
+template <typename T>
+void CompressWhitespaceHelper() {
+  T s;
+  s.AssignLiteral("abcabcabc");
+  s.CompressWhitespace(true, true);
+  EXPECT_TRUE(s.EqualsLiteral("abcabcabc"));
+
+  s.AssignLiteral("   \n\rabcabcabc\r\n");
+  s.CompressWhitespace(true, true);
+  EXPECT_TRUE(s.EqualsLiteral("abcabcabc"));
+
+  s.AssignLiteral("   \n\rabc   abc   abc\r\n");
+  s.CompressWhitespace(true, true);
+  EXPECT_TRUE(s.EqualsLiteral("abc abc abc"));
+
+  s.AssignLiteral("   \n\rabc\r   abc\n   abc\r\n");
+  s.CompressWhitespace(true, true);
+  EXPECT_TRUE(s.EqualsLiteral("abc abc abc"));
+
+  s.AssignLiteral("   \n\rabc\r  \nabc\n   \rabc\r\n");
+  s.CompressWhitespace(true, true);
+  EXPECT_TRUE(s.EqualsLiteral("abc abc abc"));
+
+  s.AssignLiteral("   \n\rabc\r   abc\n   abc\r\n");
+  s.CompressWhitespace(false, true);
+  EXPECT_TRUE(s.EqualsLiteral(" abc abc abc"));
+
+  s.AssignLiteral("   \n\rabc\r   abc\n   abc\r\n");
+  s.CompressWhitespace(true, false);
+  EXPECT_TRUE(s.EqualsLiteral("abc abc abc "));
+
+  s.AssignLiteral("   \n\rabc\r   abc\n   abc\r\n");
+  s.CompressWhitespace(false, false);
+  EXPECT_TRUE(s.EqualsLiteral(" abc abc abc "));
+
+  s.AssignLiteral("  \r\n  ");
+  s.CompressWhitespace(true, true);
+  EXPECT_TRUE(s.EqualsLiteral(""));
+
+  s.AssignLiteral("  \r\n  \t");
+  s.CompressWhitespace(true, true);
+  EXPECT_TRUE(s.EqualsLiteral(""));
+
+  s.AssignLiteral("\n  \r\n  \t");
+  s.CompressWhitespace(false, false);
+  EXPECT_TRUE(s.EqualsLiteral(" "));
+
+  s.AssignLiteral("\n  \r\n  \t");
+  s.CompressWhitespace(false, true);
+  EXPECT_TRUE(s.EqualsLiteral(""));
+
+  s.AssignLiteral("\n  \r\n  \t");
+  s.CompressWhitespace(true, false);
+  EXPECT_TRUE(s.EqualsLiteral(""));
+
+  s.AssignLiteral("");
+  s.CompressWhitespace(false, false);
+  EXPECT_TRUE(s.EqualsLiteral(""));
+
+  s.AssignLiteral("");
+  s.CompressWhitespace(false, true);
+  EXPECT_TRUE(s.EqualsLiteral(""));
+
+  s.AssignLiteral("");
+  s.CompressWhitespace(true, false);
+  EXPECT_TRUE(s.EqualsLiteral(""));
+
+  s.AssignLiteral("");
+  s.CompressWhitespace(true, true);
+  EXPECT_TRUE(s.EqualsLiteral(""));
+}
+
+TEST_F(Strings, CompressWhitespace) { CompressWhitespaceHelper<nsCString>(); }
+
+TEST_F(Strings, CompressWhitespaceW) {
+  CompressWhitespaceHelper<nsString>();
+
+  nsString str, result;
+  str.AssignLiteral(u"\u263A    is\r\n   ;-)");
+  result.AssignLiteral(u"\u263A is ;-)");
+  str.CompressWhitespace(true, true);
+  EXPECT_TRUE(str == result);
+}
+
+template <typename T>
+void StripCRLFHelper() {
+  T s;
+  s.AssignLiteral("abcabcabc");
+  s.StripCRLF();
+  EXPECT_TRUE(s.EqualsLiteral("abcabcabc"));
+
+  s.AssignLiteral("   \n\rabcabcabc\r\n");
+  s.StripCRLF();
+  EXPECT_TRUE(s.EqualsLiteral("   abcabcabc"));
+
+  s.AssignLiteral("   \n\rabc   abc   abc\r\n");
+  s.StripCRLF();
+  EXPECT_TRUE(s.EqualsLiteral("   abc   abc   abc"));
+
+  s.AssignLiteral("   \n\rabc\r   abc\n   abc\r\n");
+  s.StripCRLF();
+  EXPECT_TRUE(s.EqualsLiteral("   abc   abc   abc"));
+
+  s.AssignLiteral("   \n\rabc\r  \nabc\n   \rabc\r\n");
+  s.StripCRLF();
+  EXPECT_TRUE(s.EqualsLiteral("   abc  abc   abc"));
+
+  s.AssignLiteral("   \n\rabc\r   abc\n   abc\r\n");
+  s.StripCRLF();
+  EXPECT_TRUE(s.EqualsLiteral("   abc   abc   abc"));
+
+  s.AssignLiteral("  \r\n  ");
+  s.StripCRLF();
+  EXPECT_TRUE(s.EqualsLiteral("    "));
+
+  s.AssignLiteral("  \r\n  \t");
+  s.StripCRLF();
+  EXPECT_TRUE(s.EqualsLiteral("    \t"));
+
+  s.AssignLiteral("\n  \r\n  \t");
+  s.StripCRLF();
+  EXPECT_TRUE(s.EqualsLiteral("    \t"));
+
+  s.AssignLiteral("");
+  s.StripCRLF();
+  EXPECT_TRUE(s.EqualsLiteral(""));
+}
+
+TEST_F(Strings, StripCRLF) { StripCRLFHelper<nsCString>(); }
+
+TEST_F(Strings, StripCRLFW) {
+  StripCRLFHelper<nsString>();
+
+  nsString str, result;
+  str.AssignLiteral(u"\u263A    is\r\n   ;-)");
+  result.AssignLiteral(u"\u263A    is   ;-)");
+  str.StripCRLF();
+  EXPECT_TRUE(str == result);
+}
+
+TEST_F(Strings, utf8_to_latin1_sharing) {
+  nsCString s;
+  s.Append('a');
+  s.Append('b');
+  s.Append('c');
+  nsCString t;
+  LossyAppendUTF8toLatin1(s, t);
+  EXPECT_TRUE(t.EqualsLiteral("abc"));
+  EXPECT_EQ(s.BeginReading(), t.BeginReading());
+  LossyCopyUTF8toLatin1(s, t);
+  EXPECT_TRUE(t.EqualsLiteral("abc"));
+  EXPECT_EQ(s.BeginReading(), t.BeginReading());
+}
+
+TEST_F(Strings, latin1_to_utf8_sharing) {
+  nsCString s;
+  s.Append('a');
+  s.Append('b');
+  s.Append('c');
+  nsCString t;
+  AppendLatin1toUTF8(s, t);
+  EXPECT_TRUE(t.EqualsLiteral("abc"));
+  EXPECT_EQ(s.BeginReading(), t.BeginReading());
+  CopyLatin1toUTF8(s, t);
+  EXPECT_TRUE(t.EqualsLiteral("abc"));
+  EXPECT_EQ(s.BeginReading(), t.BeginReading());
+}
+
+TEST_F(Strings, utf8_to_latin1) {
+  nsCString s;
+  s.AssignLiteral("\xC3\xA4");
+  nsCString t;
+  LossyCopyUTF8toLatin1(s, t);
+  // EqualsLiteral requires ASCII
+  EXPECT_TRUE(t.Equals("\xE4"));
+}
+
+TEST_F(Strings, latin1_to_utf8) {
+  nsCString s;
+  s.AssignLiteral("\xE4");
+  nsCString t;
+  CopyLatin1toUTF8(s, t);
+  // EqualsLiteral requires ASCII
+  EXPECT_TRUE(t.Equals("\xC3\xA4"));
+}
+
+TEST_F(Strings, ConvertToSpan) {
+  nsString string;
+
+  // from const string
+  {
+    const auto& constStringRef = string;
+
+    auto span = Span{constStringRef};
+    static_assert(std::is_same_v<decltype(span), Span<const char16_t>>);
+  }
+
+  // from non-const string
+  {
+    auto span = Span{string};
+    static_assert(std::is_same_v<decltype(span), Span<const char16_t>>);
+  }
+
+  // get mutable data
+  {
+    auto span = string.GetMutableData();
+    static_assert(std::is_same_v<decltype(span), Span<char16_t>>);
+  }
+
+  nsCString cstring;
+
+  // from const string
+  {
+    const auto& constCStringRef = cstring;
+
+    auto span = Span{constCStringRef};
+    static_assert(std::is_same_v<decltype(span), Span<const char>>);
+  }
+
+  // from non-const string
+  {
+    auto span = Span{cstring};
+    static_assert(std::is_same_v<decltype(span), Span<const char>>);
+  }
+
+  // get mutable data
+  {
+    auto span = cstring.GetMutableData();
+    static_assert(std::is_same_v<decltype(span), Span<char>>);
+  }
+}
+
+template <typename T>
+void InsertSpanHelper() {
+  T str1, str2;
+  str1.AssignLiteral("hello world");
+  str2.AssignLiteral("span ");
+
+  T expect;
+  expect.AssignLiteral("hello span world");
+
+  Span span(str2);
+  str1.Insert(span, 6);
+  EXPECT_TRUE(str1.Equals(expect));
+}
+
+TEST_F(Strings, InsertSpan) { InsertSpanHelper<nsCString>(); }
+TEST_F(Strings, InsertSpanW) { InsertSpanHelper<nsString>(); }
+
+TEST_F(Strings, TokenizedRangeEmpty) {
+  // 8-bit strings
+  {
+    for (const auto& token : nsCCharSeparatedTokenizer(""_ns, ',').ToRange()) {
+      (void)token;
+      ADD_FAILURE();
+    }
+  }
+
+  // 16-bit strings
+  {
+    for (const auto& token : nsCharSeparatedTokenizer(u""_ns, ',').ToRange()) {
+      (void)token;
+      ADD_FAILURE();
+    }
+  }
+}
+
+TEST_F(Strings, TokenizedRangeWhitespaceOnly) {
+  // 8-bit strings
+  {
+    for (const auto& token : nsCCharSeparatedTokenizer(" "_ns, ',').ToRange()) {
+      (void)token;
+      ADD_FAILURE();
+    }
+  }
+
+  // 16-bit strings
+  {
+    for (const auto& token : nsCharSeparatedTokenizer(u" "_ns, ',').ToRange()) {
+      (void)token;
+      ADD_FAILURE();
+    }
+  }
+}
+
+TEST_F(Strings, TokenizedRangeNonEmpty) {
+  // 8-bit strings
+  {
+    nsTArray<nsCString> res;
+    for (const auto& token :
+         nsCCharSeparatedTokenizer("foo,bar"_ns, ',').ToRange()) {
+      res.EmplaceBack(token);
+    }
+
+    EXPECT_EQ(res, (nsTArray<nsCString>{"foo"_ns, "bar"_ns}));
+  }
+
+  // 16-bit strings
+  {
+    nsTArray<nsString> res;
+    for (const auto& token :
+         nsCharSeparatedTokenizer(u"foo,bar"_ns, ',').ToRange()) {
+      res.EmplaceBack(token);
+    }
+
+    EXPECT_EQ(res, (nsTArray<nsString>{u"foo"_ns, u"bar"_ns}));
+  }
+}
+
+// Macros for reducing verbosity of printf tests.
+#define create_printf_strings(format, ...)                 \
+  nsCString appendPrintfString;                            \
+  appendPrintfString.AppendPrintf(format, __VA_ARGS__);    \
+  const nsCString appendVprintfString(                     \
+      getAppendVprintfString(format, __VA_ARGS__));        \
+  const nsPrintfCString printfString(format, __VA_ARGS__); \
+  const nsVprintfCString vprintfString{getVprintfCString(format, __VA_ARGS__)};
+
+// We don't check every possible combination as we assume equality is
+// transitive.
+#define verify_printf_strings(expected)                                     \
+  EXPECT_TRUE(appendPrintfString.EqualsASCII(expected))                     \
+      << "appendPrintfString != expected:" << appendPrintfString.get()      \
+      << " != " << (expected);                                              \
+  EXPECT_TRUE(appendPrintfString.Equals(appendVprintfString))               \
+      << "appendPrintfString != appendVprintfString:"                       \
+      << appendPrintfString.get() << " != " << appendVprintfString;         \
+  EXPECT_TRUE(appendPrintfString.Equals(printfString))                      \
+      << "appendPrintfString != printfString:" << appendPrintfString.get()  \
+      << " != " << printfString;                                            \
+  EXPECT_TRUE(appendPrintfString.Equals(vprintfString))                     \
+      << "appendPrintfString != vprintfString:" << appendPrintfString.get() \
+      << " != " << vprintfString;
+
+TEST_F(Strings, printf) {
+  auto getAppendVprintfString = [](const char* aFormat, ...) {
+    // Helper to get a string with contents set via AppendVprint.
+    nsCString cString;
+    va_list ap;
+    va_start(ap, aFormat);
+    cString.AppendVprintf(aFormat, ap);
+    va_end(ap);
+    return cString;
+  };
+
+  auto getVprintfCString = [](const char* aFormat, ...) {
+    // Helper to get a nsVprintfCString.
+    va_list ap;
+    va_start(ap, aFormat);
+    const nsVprintfCString vprintfString(aFormat, ap);
+    va_end(ap);
+    return vprintfString;
+  };
+
+  {
+    const char* format = "Characters %c %%";
+    const char* expectedOutput = "Characters B %";
+    create_printf_strings(format, 'B');
+    verify_printf_strings(expectedOutput);
+  }
+  {
+    const char* format = "Strings %s %s";
+    const char* expectedOutput = "Strings foo bar";
+    create_printf_strings(format, "foo", "bar");
+    verify_printf_strings(expectedOutput);
+  }
+  {
+    const int signedThree = 3;
+    const unsigned int unsignedTen = 10;
+    const char* format = "Integers %i %.3d %.2u %o %x %X";
+    const char* expectedOutput = "Integers 3 003 10 12 a A";
+    create_printf_strings(format, signedThree, signedThree, unsignedTen,
+                          unsignedTen, unsignedTen, unsignedTen);
+    verify_printf_strings(expectedOutput);
+  }
+  {
+    const char* format = "Floats %f %.0f %e %.2E";
+    const char* expectedOutput = "Floats 1.500000 2 1.500000e+00 1.50E+00";
+    create_printf_strings(format, 1.5, 1.5, 1.5, 1.5);
+    verify_printf_strings(expectedOutput);
+  }
+  {
+    const char* expectedOutput = "Just a string";
+    const char* format = "%s";
+    create_printf_strings(format, "Just a string");
+    verify_printf_strings(expectedOutput);
+  }
+  {
+    const char* anotherString = "another string";
+    const char* format = "Just a string and %s";
+    const char* expectedOutput = "Just a string and another string";
+    create_printf_strings(format, anotherString);
+    verify_printf_strings(expectedOutput);
+  }
+  {
+    // This case tickles an unexpected overload resolution in MSVC where a
+    // va_list overload will be selected if available. See bug 1673670 and
+    // 1673917 for more detail.
+    char anotherString[] = "another string";
+    const char* format = "Just a string and %s";
+    const char* expectedOutput = "Just a string and another string";
+    // Calling with a non-const pointer triggers selection of va_list overload
+    // in MSVC at time of writing
+    create_printf_strings(format, (char*)anotherString);
+    verify_printf_strings(expectedOutput);
+  }
+}
+
+// We don't need these macros following the printf test.
+#undef verify_printf_strings
+#undef create_printf_strings
+
+// Note the five calls in the loop, so divide by 100k
+MOZ_GTEST_BENCH_F(Strings, PerfStripWhitespace, [this] {
+  nsCString test1(mExample1Utf8);
+  nsCString test2(mExample2Utf8);
+  nsCString test3(mExample3Utf8);
+  nsCString test4(mExample4Utf8);
+  nsCString test5(mExample5Utf8);
+  for (int i = 0; i < 20000; i++) {
+    test1.StripWhitespace();
+    test2.StripWhitespace();
+    test3.StripWhitespace();
+    test4.StripWhitespace();
+    test5.StripWhitespace();
+  }
+});
+
+MOZ_GTEST_BENCH_F(Strings, PerfStripCharsWhitespace, [this] {
+  // This is the unoptimized (original) version of
+  // StripWhitespace using StripChars.
+  nsCString test1(mExample1Utf8);
+  nsCString test2(mExample2Utf8);
+  nsCString test3(mExample3Utf8);
+  nsCString test4(mExample4Utf8);
+  nsCString test5(mExample5Utf8);
+  for (int i = 0; i < 20000; i++) {
+    test1.StripChars("\f\t\r\n ");
+    test2.StripChars("\f\t\r\n ");
+    test3.StripChars("\f\t\r\n ");
+    test4.StripChars("\f\t\r\n ");
+    test5.StripChars("\f\t\r\n ");
+  }
+});
+
+MOZ_GTEST_BENCH_F(Strings, PerfCompressWhitespace, [this] {
+  nsCString test1(mExample1Utf8);
+  nsCString test2(mExample2Utf8);
+  nsCString test3(mExample3Utf8);
+  nsCString test4(mExample4Utf8);
+  nsCString test5(mExample5Utf8);
+  for (int i = 0; i < 20000; i++) {
+    test1.CompressWhitespace();
+    test2.CompressWhitespace();
+    test3.CompressWhitespace();
+    test4.CompressWhitespace();
+    test5.CompressWhitespace();
+  }
+});
+
+MOZ_GTEST_BENCH_F(Strings, PerfStripCRLF, [this] {
+  nsCString test1(mExample1Utf8);
+  nsCString test2(mExample2Utf8);
+  nsCString test3(mExample3Utf8);
+  nsCString test4(mExample4Utf8);
+  nsCString test5(mExample5Utf8);
+  for (int i = 0; i < 20000; i++) {
+    test1.StripCRLF();
+    test2.StripCRLF();
+    test3.StripCRLF();
+    test4.StripCRLF();
+    test5.StripCRLF();
+  }
+});
+
+MOZ_GTEST_BENCH_F(Strings, PerfStripCharsCRLF, [this] {
+  // This is the unoptimized (original) version of
+  // stripping \r\n using StripChars.
+  nsCString test1(mExample1Utf8);
+  nsCString test2(mExample2Utf8);
+  nsCString test3(mExample3Utf8);
+  nsCString test4(mExample4Utf8);
+  nsCString test5(mExample5Utf8);
+  for (int i = 0; i < 20000; i++) {
+    test1.StripChars("\r\n");
+    test2.StripChars("\r\n");
+    test3.StripChars("\r\n");
+    test4.StripChars("\r\n");
+    test5.StripChars("\r\n");
+  }
+});
+
+MOZ_GTEST_BENCH_F(Strings, PerfIsUTF8One, [this] {
+  for (int i = 0; i < 200000; i++) {
+    bool b = IsUtf8(*BlackBox(&mAsciiOneUtf8));
+    BlackBox(&b);
+  }
+});
+
+MOZ_GTEST_BENCH_F(Strings, PerfIsUTF8Fifteen, [this] {
+  for (int i = 0; i < 200000; i++) {
+    bool b = IsUtf8(*BlackBox(&mAsciiFifteenUtf8));
+    BlackBox(&b);
+  }
+});
+
+MOZ_GTEST_BENCH_F(Strings, PerfIsUTF8Hundred, [this] {
+  for (int i = 0; i < 200000; i++) {
+    bool b = IsUtf8(*BlackBox(&mAsciiHundredUtf8));
+    BlackBox(&b);
+  }
+});
+
+MOZ_GTEST_BENCH_F(Strings, PerfIsUTF8Example3, [this] {
+  for (int i = 0; i < 100000; i++) {
+    bool b = IsUtf8(*BlackBox(&mExample3Utf8));
+    BlackBox(&b);
+  }
+});
+
+MOZ_GTEST_BENCH_F(Strings, PerfIsASCII8One, [this] {
+  for (int i = 0; i < 200000; i++) {
+    bool b = IsAscii(*BlackBox(&mAsciiOneUtf8));
+    BlackBox(&b);
+  }
+});
+
+MOZ_GTEST_BENCH_F(Strings, PerfIsASCIIFifteen, [this] {
+  for (int i = 0; i < 200000; i++) {
+    bool b = IsAscii(*BlackBox(&mAsciiFifteenUtf8));
+    BlackBox(&b);
+  }
+});
+
+MOZ_GTEST_BENCH_F(Strings, PerfIsASCIIHundred, [this] {
+  for (int i = 0; i < 200000; i++) {
+    bool b = IsAscii(*BlackBox(&mAsciiHundredUtf8));
+    BlackBox(&b);
+  }
+});
+
+MOZ_GTEST_BENCH_F(Strings, PerfIsASCIIExample3, [this] {
+  for (int i = 0; i < 100000; i++) {
+    bool b = IsAscii(*BlackBox(&mExample3Utf8));
+    BlackBox(&b);
+  }
+});
+
+MOZ_GTEST_BENCH_F(Strings, PerfHasRTLCharsExample3, [this] {
+  for (int i = 0; i < 5000; i++) {
+    bool b = HasRTLChars(*BlackBox(&mExample3Utf16));
+    BlackBox(&b);
+  }
+});
+
+MOZ_GTEST_BENCH_F(Strings, PerfHasRTLCharsDE, [this] {
+  for (int i = 0; i < 5000; i++) {
+    bool b = HasRTLChars(*BlackBox(&mDeUtf16));
+    BlackBox(&b);
+  }
+});
+
+MOZ_GTEST_BENCH_F(Strings, PerfHasRTLCharsRU, [this] {
+  for (int i = 0; i < 5000; i++) {
+    bool b = HasRTLChars(*BlackBox(&mRuUtf16));
+    BlackBox(&b);
+  }
+});
+
+MOZ_GTEST_BENCH_F(Strings, PerfHasRTLCharsTH, [this] {
+  for (int i = 0; i < 5000; i++) {
+    bool b = HasRTLChars(*BlackBox(&mThUtf16));
+    BlackBox(&b);
+  }
+});
+
+MOZ_GTEST_BENCH_F(Strings, PerfHasRTLCharsJA, [this] {
+  for (int i = 0; i < 5000; i++) {
+    bool b = HasRTLChars(*BlackBox(&mJaUtf16));
+    BlackBox(&b);
+  }
+});
+
+CONVERSION_BENCH(PerfUTF16toLatin1ASCIIOne, LossyCopyUTF16toASCII,
+                 mAsciiOneUtf16, nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF16toLatin1ASCIIThree, LossyCopyUTF16toASCII,
+                 mAsciiThreeUtf16, nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF16toLatin1ASCIIFifteen, LossyCopyUTF16toASCII,
+                 mAsciiFifteenUtf16, nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF16toLatin1ASCIIHundred, LossyCopyUTF16toASCII,
+                 mAsciiHundredUtf16, nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF16toLatin1ASCIIThousand, LossyCopyUTF16toASCII,
+                 mAsciiThousandUtf16, nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF16toLatin1DEOne, LossyCopyUTF16toASCII, mDeEditOneUtf16,
+                 nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF16toLatin1DEThree, LossyCopyUTF16toASCII,
+                 mDeEditThreeUtf16, nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF16toLatin1DEFifteen, LossyCopyUTF16toASCII,
+                 mDeEditFifteenUtf16, nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF16toLatin1DEHundred, LossyCopyUTF16toASCII,
+                 mDeEditHundredUtf16, nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF16toLatin1DEThousand, LossyCopyUTF16toASCII,
+                 mDeEditThousandUtf16, nsAutoCString);
+
+CONVERSION_BENCH(PerfLatin1toUTF16AsciiOne, CopyASCIItoUTF16, mAsciiOneUtf8,
+                 nsAutoString);
+
+CONVERSION_BENCH(PerfLatin1toUTF16AsciiThree, CopyASCIItoUTF16, mAsciiThreeUtf8,
+                 nsAutoString);
+
+CONVERSION_BENCH(PerfLatin1toUTF16AsciiFifteen, CopyASCIItoUTF16,
+                 mAsciiFifteenUtf8, nsAutoString);
+
+CONVERSION_BENCH(PerfLatin1toUTF16AsciiHundred, CopyASCIItoUTF16,
+                 mAsciiHundredUtf8, nsAutoString);
+
+CONVERSION_BENCH(PerfLatin1toUTF16AsciiThousand, CopyASCIItoUTF16,
+                 mAsciiThousandUtf8, nsAutoString);
+
+CONVERSION_BENCH(PerfLatin1toUTF16DEOne, CopyASCIItoUTF16, mDeEditOneLatin1,
+                 nsAutoString);
+
+CONVERSION_BENCH(PerfLatin1toUTF16DEThree, CopyASCIItoUTF16, mDeEditThreeLatin1,
+                 nsAutoString);
+
+CONVERSION_BENCH(PerfLatin1toUTF16DEFifteen, CopyASCIItoUTF16,
+                 mDeEditFifteenLatin1, nsAutoString);
+
+CONVERSION_BENCH(PerfLatin1toUTF16DEHundred, CopyASCIItoUTF16,
+                 mDeEditHundredLatin1, nsAutoString);
+
+CONVERSION_BENCH(PerfLatin1toUTF16DEThousand, CopyASCIItoUTF16,
+                 mDeEditThousandLatin1, nsAutoString);
+
+CONVERSION_BENCH(PerfUTF16toUTF8AsciiOne, CopyUTF16toUTF8, mAsciiOneUtf16,
+                 nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF16toUTF8AsciiThree, CopyUTF16toUTF8, mAsciiThreeUtf16,
+                 nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF16toUTF8AsciiFifteen, CopyUTF16toUTF8,
+                 mAsciiFifteenUtf16, nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF16toUTF8AsciiHundred, CopyUTF16toUTF8,
+                 mAsciiHundredUtf16, nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF16toUTF8AsciiThousand, CopyUTF16toUTF8,
+                 mAsciiThousandUtf16, nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF8toUTF16AsciiOne, CopyUTF8toUTF16, mAsciiOneUtf8,
+                 nsAutoString);
+
+CONVERSION_BENCH(PerfUTF8toUTF16AsciiThree, CopyUTF8toUTF16, mAsciiThreeUtf8,
+                 nsAutoString);
+
+CONVERSION_BENCH(PerfUTF8toUTF16AsciiFifteen, CopyUTF8toUTF16,
+                 mAsciiFifteenUtf8, nsAutoString);
+
+CONVERSION_BENCH(PerfUTF8toUTF16AsciiHundred, CopyUTF8toUTF16,
+                 mAsciiHundredUtf8, nsAutoString);
+
+CONVERSION_BENCH(PerfUTF8toUTF16AsciiThousand, CopyUTF8toUTF16,
+                 mAsciiThousandUtf8, nsAutoString);
+
+CONVERSION_BENCH(PerfUTF16toUTF8AROne, CopyUTF16toUTF8, mArOneUtf16,
+                 nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF16toUTF8ARThree, CopyUTF16toUTF8, mArThreeUtf16,
+                 nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF16toUTF8ARFifteen, CopyUTF16toUTF8, mArFifteenUtf16,
+                 nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF16toUTF8ARHundred, CopyUTF16toUTF8, mArHundredUtf16,
+                 nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF16toUTF8ARThousand, CopyUTF16toUTF8, mArThousandUtf16,
+                 nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF8toUTF16AROne, CopyUTF8toUTF16, mArOneUtf8,
+                 nsAutoString);
+
+CONVERSION_BENCH(PerfUTF8toUTF16ARThree, CopyUTF8toUTF16, mArThreeUtf8,
+                 nsAutoString);
+
+CONVERSION_BENCH(PerfUTF8toUTF16ARFifteen, CopyUTF8toUTF16, mArFifteenUtf8,
+                 nsAutoString);
+
+CONVERSION_BENCH(PerfUTF8toUTF16ARHundred, CopyUTF8toUTF16, mArHundredUtf8,
+                 nsAutoString);
+
+CONVERSION_BENCH(PerfUTF8toUTF16ARThousand, CopyUTF8toUTF16, mArThousandUtf8,
+                 nsAutoString);
+
+CONVERSION_BENCH(PerfUTF16toUTF8DEOne, CopyUTF16toUTF8, mDeOneUtf16,
+                 nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF16toUTF8DEThree, CopyUTF16toUTF8, mDeThreeUtf16,
+                 nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF16toUTF8DEFifteen, CopyUTF16toUTF8, mDeFifteenUtf16,
+                 nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF16toUTF8DEHundred, CopyUTF16toUTF8, mDeHundredUtf16,
+                 nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF16toUTF8DEThousand, CopyUTF16toUTF8, mDeThousandUtf16,
+                 nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF8toUTF16DEOne, CopyUTF8toUTF16, mDeOneUtf8,
+                 nsAutoString);
+
+CONVERSION_BENCH(PerfUTF8toUTF16DEThree, CopyUTF8toUTF16, mDeThreeUtf8,
+                 nsAutoString);
+
+CONVERSION_BENCH(PerfUTF8toUTF16DEFifteen, CopyUTF8toUTF16, mDeFifteenUtf8,
+                 nsAutoString);
+
+CONVERSION_BENCH(PerfUTF8toUTF16DEHundred, CopyUTF8toUTF16, mDeHundredUtf8,
+                 nsAutoString);
+
+CONVERSION_BENCH(PerfUTF8toUTF16DEThousand, CopyUTF8toUTF16, mDeThousandUtf8,
+                 nsAutoString);
+
+CONVERSION_BENCH(PerfUTF16toUTF8RUOne, CopyUTF16toUTF8, mRuOneUtf16,
+                 nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF16toUTF8RUThree, CopyUTF16toUTF8, mRuThreeUtf16,
+                 nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF16toUTF8RUFifteen, CopyUTF16toUTF8, mRuFifteenUtf16,
+                 nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF16toUTF8RUHundred, CopyUTF16toUTF8, mRuHundredUtf16,
+                 nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF16toUTF8RUThousand, CopyUTF16toUTF8, mRuThousandUtf16,
+                 nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF8toUTF16RUOne, CopyUTF8toUTF16, mRuOneUtf8,
+                 nsAutoString);
+
+CONVERSION_BENCH(PerfUTF8toUTF16RUThree, CopyUTF8toUTF16, mRuThreeUtf8,
+                 nsAutoString);
+
+CONVERSION_BENCH(PerfUTF8toUTF16RUFifteen, CopyUTF8toUTF16, mRuFifteenUtf8,
+                 nsAutoString);
+
+CONVERSION_BENCH(PerfUTF8toUTF16RUHundred, CopyUTF8toUTF16, mRuHundredUtf8,
+                 nsAutoString);
+
+CONVERSION_BENCH(PerfUTF8toUTF16RUThousand, CopyUTF8toUTF16, mRuThousandUtf8,
+                 nsAutoString);
+
+CONVERSION_BENCH(PerfUTF16toUTF8THOne, CopyUTF16toUTF8, mThOneUtf16,
+                 nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF16toUTF8THThree, CopyUTF16toUTF8, mThThreeUtf16,
+                 nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF16toUTF8THFifteen, CopyUTF16toUTF8, mThFifteenUtf16,
+                 nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF16toUTF8THHundred, CopyUTF16toUTF8, mThHundredUtf16,
+                 nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF16toUTF8THThousand, CopyUTF16toUTF8, mThThousandUtf16,
+                 nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF8toUTF16THOne, CopyUTF8toUTF16, mThOneUtf8,
+                 nsAutoString);
+
+CONVERSION_BENCH(PerfUTF8toUTF16THThree, CopyUTF8toUTF16, mThThreeUtf8,
+                 nsAutoString);
+
+CONVERSION_BENCH(PerfUTF8toUTF16THFifteen, CopyUTF8toUTF16, mThFifteenUtf8,
+                 nsAutoString);
+
+CONVERSION_BENCH(PerfUTF8toUTF16THHundred, CopyUTF8toUTF16, mThHundredUtf8,
+                 nsAutoString);
+
+CONVERSION_BENCH(PerfUTF8toUTF16THThousand, CopyUTF8toUTF16, mThThousandUtf8,
+                 nsAutoString);
+
+CONVERSION_BENCH(PerfUTF16toUTF8JAOne, CopyUTF16toUTF8, mJaOneUtf16,
+                 nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF16toUTF8JAThree, CopyUTF16toUTF8, mJaThreeUtf16,
+                 nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF16toUTF8JAFifteen, CopyUTF16toUTF8, mJaFifteenUtf16,
+                 nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF16toUTF8JAHundred, CopyUTF16toUTF8, mJaHundredUtf16,
+                 nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF16toUTF8JAThousand, CopyUTF16toUTF8, mJaThousandUtf16,
+                 nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF8toUTF16JAOne, CopyUTF8toUTF16, mJaOneUtf8,
+                 nsAutoString);
+
+CONVERSION_BENCH(PerfUTF8toUTF16JAThree, CopyUTF8toUTF16, mJaThreeUtf8,
+                 nsAutoString);
+
+CONVERSION_BENCH(PerfUTF8toUTF16JAFifteen, CopyUTF8toUTF16, mJaFifteenUtf8,
+                 nsAutoString);
+
+CONVERSION_BENCH(PerfUTF8toUTF16JAHundred, CopyUTF8toUTF16, mJaHundredUtf8,
+                 nsAutoString);
+
+CONVERSION_BENCH(PerfUTF8toUTF16JAThousand, CopyUTF8toUTF16, mJaThousandUtf8,
+                 nsAutoString);
+
+CONVERSION_BENCH(PerfUTF16toUTF8KOOne, CopyUTF16toUTF8, mKoOneUtf16,
+                 nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF16toUTF8KOThree, CopyUTF16toUTF8, mKoThreeUtf16,
+                 nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF16toUTF8KOFifteen, CopyUTF16toUTF8, mKoFifteenUtf16,
+                 nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF16toUTF8KOHundred, CopyUTF16toUTF8, mKoHundredUtf16,
+                 nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF16toUTF8KOThousand, CopyUTF16toUTF8, mKoThousandUtf16,
+                 nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF8toUTF16KOOne, CopyUTF8toUTF16, mKoOneUtf8,
+                 nsAutoString);
+
+CONVERSION_BENCH(PerfUTF8toUTF16KOThree, CopyUTF8toUTF16, mKoThreeUtf8,
+                 nsAutoString);
+
+CONVERSION_BENCH(PerfUTF8toUTF16KOFifteen, CopyUTF8toUTF16, mKoFifteenUtf8,
+                 nsAutoString);
+
+CONVERSION_BENCH(PerfUTF8toUTF16KOHundred, CopyUTF8toUTF16, mKoHundredUtf8,
+                 nsAutoString);
+
+CONVERSION_BENCH(PerfUTF8toUTF16KOThousand, CopyUTF8toUTF16, mKoThousandUtf8,
+                 nsAutoString);
+
+CONVERSION_BENCH(PerfUTF16toUTF8TROne, CopyUTF16toUTF8, mTrOneUtf16,
+                 nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF16toUTF8TRThree, CopyUTF16toUTF8, mTrThreeUtf16,
+                 nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF16toUTF8TRFifteen, CopyUTF16toUTF8, mTrFifteenUtf16,
+                 nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF16toUTF8TRHundred, CopyUTF16toUTF8, mTrHundredUtf16,
+                 nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF16toUTF8TRThousand, CopyUTF16toUTF8, mTrThousandUtf16,
+                 nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF8toUTF16TROne, CopyUTF8toUTF16, mTrOneUtf8,
+                 nsAutoString);
+
+CONVERSION_BENCH(PerfUTF8toUTF16TRThree, CopyUTF8toUTF16, mTrThreeUtf8,
+                 nsAutoString);
+
+CONVERSION_BENCH(PerfUTF8toUTF16TRFifteen, CopyUTF8toUTF16, mTrFifteenUtf8,
+                 nsAutoString);
+
+CONVERSION_BENCH(PerfUTF8toUTF16TRHundred, CopyUTF8toUTF16, mTrHundredUtf8,
+                 nsAutoString);
+
+CONVERSION_BENCH(PerfUTF8toUTF16TRThousand, CopyUTF8toUTF16, mTrThousandUtf8,
+                 nsAutoString);
+
+CONVERSION_BENCH(PerfUTF16toUTF8VIOne, CopyUTF16toUTF8, mViOneUtf16,
+                 nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF16toUTF8VIThree, CopyUTF16toUTF8, mViThreeUtf16,
+                 nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF16toUTF8VIFifteen, CopyUTF16toUTF8, mViFifteenUtf16,
+                 nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF16toUTF8VIHundred, CopyUTF16toUTF8, mViHundredUtf16,
+                 nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF16toUTF8VIThousand, CopyUTF16toUTF8, mViThousandUtf16,
+                 nsAutoCString);
+
+CONVERSION_BENCH(PerfUTF8toUTF16VIOne, CopyUTF8toUTF16, mViOneUtf8,
+                 nsAutoString);
+
+CONVERSION_BENCH(PerfUTF8toUTF16VIThree, CopyUTF8toUTF16, mViThreeUtf8,
+                 nsAutoString);
+
+CONVERSION_BENCH(PerfUTF8toUTF16VIFifteen, CopyUTF8toUTF16, mViFifteenUtf8,
+                 nsAutoString);
+
+CONVERSION_BENCH(PerfUTF8toUTF16VIHundred, CopyUTF8toUTF16, mViHundredUtf8,
+                 nsAutoString);
+
+CONVERSION_BENCH(PerfUTF8toUTF16VIThousand, CopyUTF8toUTF16, mViThousandUtf8,
+                 nsAutoString);
+
+// Tests for usability of nsTLiteralString in constant expressions.
+static_assert(u""_ns.IsEmpty());
+
+constexpr auto testStringA = u"a"_ns;
+static_assert(!testStringA.IsEmpty());
+static_assert(!testStringA.IsVoid());
+static_assert(testStringA.IsLiteral());
+static_assert(testStringA.IsTerminated());
+static_assert(testStringA.GetDataFlags() ==
+              (nsLiteralString::DataFlags::LITERAL |
+               nsLiteralString::DataFlags::TERMINATED));
+static_assert(*static_cast<const char16_t*>(testStringA.Data()) == 'a');
+static_assert(1 == testStringA.Length());
+static_assert(testStringA.CharAt(0) == 'a');
+static_assert(testStringA[0] == 'a');
+static_assert(*testStringA.BeginReading() == 'a');
+static_assert(*testStringA.EndReading() == 0);
+static_assert(testStringA.EndReading() - testStringA.BeginReading() == 1);
+
+}  // namespace TestStrings
+
+#if defined(__clang__) && (__clang_major__ >= 6)
+#  pragma clang diagnostic pop
+#endif