about summary refs log tree commit diff
path: root/absl/strings/cord_test.cc
diff options
context:
space:
mode:
Diffstat (limited to 'absl/strings/cord_test.cc')
-rw-r--r--absl/strings/cord_test.cc1526
1 files changed, 1526 insertions, 0 deletions
diff --git a/absl/strings/cord_test.cc b/absl/strings/cord_test.cc
new file mode 100644
index 000000000000..434f3a247e08
--- /dev/null
+++ b/absl/strings/cord_test.cc
@@ -0,0 +1,1526 @@
+#include "absl/strings/cord.h"
+
+#include <algorithm>
+#include <climits>
+#include <cstdio>
+#include <iterator>
+#include <map>
+#include <numeric>
+#include <random>
+#include <sstream>
+#include <type_traits>
+#include <utility>
+#include <vector>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "absl/base/casts.h"
+#include "absl/base/config.h"
+#include "absl/base/internal/endian.h"
+#include "absl/base/internal/raw_logging.h"
+#include "absl/container/fixed_array.h"
+#include "absl/strings/cord_test_helpers.h"
+#include "absl/strings/str_cat.h"
+#include "absl/strings/string_view.h"
+
+typedef std::mt19937_64 RandomEngine;
+
+static std::string RandomLowercaseString(RandomEngine* rng);
+static std::string RandomLowercaseString(RandomEngine* rng, size_t length);
+
+static int GetUniformRandomUpTo(RandomEngine* rng, int upper_bound) {
+  if (upper_bound > 0) {
+    std::uniform_int_distribution<int> uniform(0, upper_bound - 1);
+    return uniform(*rng);
+  } else {
+    return 0;
+  }
+}
+
+static size_t GetUniformRandomUpTo(RandomEngine* rng, size_t upper_bound) {
+  if (upper_bound > 0) {
+    std::uniform_int_distribution<size_t> uniform(0, upper_bound - 1);
+    return uniform(*rng);
+  } else {
+    return 0;
+  }
+}
+
+static int32_t GenerateSkewedRandom(RandomEngine* rng, int max_log) {
+  const uint32_t base = (*rng)() % (max_log + 1);
+  const uint32_t mask = ((base < 32) ? (1u << base) : 0u) - 1u;
+  return (*rng)() & mask;
+}
+
+static std::string RandomLowercaseString(RandomEngine* rng) {
+  int length;
+  std::bernoulli_distribution one_in_1k(0.001);
+  std::bernoulli_distribution one_in_10k(0.0001);
+  // With low probability, make a large fragment
+  if (one_in_10k(*rng)) {
+    length = GetUniformRandomUpTo(rng, 1048576);
+  } else if (one_in_1k(*rng)) {
+    length = GetUniformRandomUpTo(rng, 10000);
+  } else {
+    length = GenerateSkewedRandom(rng, 10);
+  }
+  return RandomLowercaseString(rng, length);
+}
+
+static std::string RandomLowercaseString(RandomEngine* rng, size_t length) {
+  std::string result(length, '\0');
+  std::uniform_int_distribution<int> chars('a', 'z');
+  std::generate(result.begin(), result.end(), [&]() {
+    return static_cast<char>(chars(*rng));
+  });
+  return result;
+}
+
+static void DoNothing(absl::string_view /* data */, void* /* arg */) {}
+
+static void DeleteExternalString(absl::string_view data, void* arg) {
+  std::string* s = reinterpret_cast<std::string*>(arg);
+  EXPECT_EQ(data, *s);
+  delete s;
+}
+
+// Add "s" to *dst via `MakeCordFromExternal`
+static void AddExternalMemory(absl::string_view s, absl::Cord* dst) {
+  std::string* str = new std::string(s.data(), s.size());
+  dst->Append(absl::MakeCordFromExternal(*str, [str](absl::string_view data) {
+    DeleteExternalString(data, str);
+  }));
+}
+
+static void DumpGrowth() {
+  absl::Cord str;
+  for (int i = 0; i < 1000; i++) {
+    char c = 'a' + i % 26;
+    str.Append(absl::string_view(&c, 1));
+  }
+}
+
+// Make a Cord with some number of fragments.  Return the size (in bytes)
+// of the smallest fragment.
+static size_t AppendWithFragments(const std::string& s, RandomEngine* rng,
+                                  absl::Cord* cord) {
+  size_t j = 0;
+  const size_t max_size = s.size() / 5;  // Make approx. 10 fragments
+  size_t min_size = max_size;            // size of smallest fragment
+  while (j < s.size()) {
+    size_t N = 1 + GetUniformRandomUpTo(rng, max_size);
+    if (N > (s.size() - j)) {
+      N = s.size() - j;
+    }
+    if (N < min_size) {
+      min_size = N;
+    }
+
+    std::bernoulli_distribution coin_flip(0.5);
+    if (coin_flip(*rng)) {
+      // Grow by adding an external-memory.
+      AddExternalMemory(absl::string_view(s.data() + j, N), cord);
+    } else {
+      cord->Append(absl::string_view(s.data() + j, N));
+    }
+    j += N;
+  }
+  return min_size;
+}
+
+// Add an external memory that contains the specified std::string to cord
+static void AddNewStringBlock(const std::string& str, absl::Cord* dst) {
+  char* data = new char[str.size()];
+  memcpy(data, str.data(), str.size());
+  dst->Append(absl::MakeCordFromExternal(
+      absl::string_view(data, str.size()),
+      [](absl::string_view s) { delete[] s.data(); }));
+}
+
+// Make a Cord out of many different types of nodes.
+static absl::Cord MakeComposite() {
+  absl::Cord cord;
+  cord.Append("the");
+  AddExternalMemory(" quick brown", &cord);
+  AddExternalMemory(" fox jumped", &cord);
+
+  absl::Cord full(" over");
+  AddExternalMemory(" the lazy", &full);
+  AddNewStringBlock(" dog slept the whole day away", &full);
+  absl::Cord substring = full.Subcord(0, 18);
+
+  // Make substring long enough to defeat the copying fast path in Append.
+  substring.Append(std::string(1000, '.'));
+  cord.Append(substring);
+  cord = cord.Subcord(0, cord.size() - 998);  // Remove most of extra junk
+
+  return cord;
+}
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+class CordTestPeer {
+ public:
+  static void ForEachChunk(
+      const Cord& c, absl::FunctionRef<void(absl::string_view)> callback) {
+    c.ForEachChunk(callback);
+  }
+};
+
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+TEST(Cord, AllFlatSizes) {
+  using absl::strings_internal::CordTestAccess;
+
+  for (size_t s = 0; s < CordTestAccess::MaxFlatLength(); s++) {
+    // Make a std::string of length s.
+    std::string src;
+    while (src.size() < s) {
+      src.push_back('a' + (src.size() % 26));
+    }
+
+    absl::Cord dst(src);
+    EXPECT_EQ(std::string(dst), src) << s;
+  }
+}
+
+// We create a Cord at least 128GB in size using the fact that Cords can
+// internally reference-count; thus the Cord is enormous without actually
+// consuming very much memory.
+TEST(GigabyteCord, FromExternal) {
+  const size_t one_gig = 1024U * 1024U * 1024U;
+  size_t max_size = 2 * one_gig;
+  if (sizeof(max_size) > 4) max_size = 128 * one_gig;
+
+  size_t length = 128 * 1024;
+  char* data = new char[length];
+  absl::Cord from = absl::MakeCordFromExternal(
+      absl::string_view(data, length),
+      [](absl::string_view sv) { delete[] sv.data(); });
+
+  // This loop may seem odd due to its combination of exponential doubling of
+  // size and incremental size increases.  We do it incrementally to be sure the
+  // Cord will need rebalancing and will exercise code that, in the past, has
+  // caused crashes in production.  We grow exponentially so that the code will
+  // execute in a reasonable amount of time.
+  absl::Cord c;
+  ABSL_RAW_LOG(INFO, "Made a Cord with %zu bytes!", c.size());
+  c.Append(from);
+  while (c.size() < max_size) {
+    c.Append(c);
+    c.Append(from);
+    c.Append(from);
+    c.Append(from);
+    c.Append(from);
+  }
+
+  for (int i = 0; i < 1024; ++i) {
+    c.Append(from);
+  }
+  ABSL_RAW_LOG(INFO, "Made a Cord with %zu bytes!", c.size());
+  // Note: on a 32-bit build, this comes out to   2,818,048,000 bytes.
+  // Note: on a 64-bit build, this comes out to 171,932,385,280 bytes.
+}
+
+static absl::Cord MakeExternalCord(int size) {
+  char* buffer = new char[size];
+  memset(buffer, 'x', size);
+  absl::Cord cord;
+  cord.Append(absl::MakeCordFromExternal(
+      absl::string_view(buffer, size),
+      [](absl::string_view s) { delete[] s.data(); }));
+  return cord;
+}
+
+// Extern to fool clang that this is not constant. Needed to suppress
+// a warning of unsafe code we want to test.
+extern bool my_unique_true_boolean;
+bool my_unique_true_boolean = true;
+
+TEST(Cord, Assignment) {
+  absl::Cord x(absl::string_view("hi there"));
+  absl::Cord y(x);
+  ASSERT_EQ(std::string(x), "hi there");
+  ASSERT_EQ(std::string(y), "hi there");
+  ASSERT_TRUE(x == y);
+  ASSERT_TRUE(x <= y);
+  ASSERT_TRUE(y <= x);
+
+  x = absl::string_view("foo");
+  ASSERT_EQ(std::string(x), "foo");
+  ASSERT_EQ(std::string(y), "hi there");
+  ASSERT_TRUE(x < y);
+  ASSERT_TRUE(y > x);
+  ASSERT_TRUE(x != y);
+  ASSERT_TRUE(x <= y);
+  ASSERT_TRUE(y >= x);
+
+  x = "foo";
+  ASSERT_EQ(x, "foo");
+
+  // Test that going from inline rep to tree we don't leak memory.
+  std::vector<std::pair<absl::string_view, absl::string_view>>
+      test_string_pairs = {{"hi there", "foo"},
+                           {"loooooong coooooord", "short cord"},
+                           {"short cord", "loooooong coooooord"},
+                           {"loooooong coooooord1", "loooooong coooooord2"}};
+  for (std::pair<absl::string_view, absl::string_view> test_strings :
+       test_string_pairs) {
+    absl::Cord tmp(test_strings.first);
+    absl::Cord z(std::move(tmp));
+    ASSERT_EQ(std::string(z), test_strings.first);
+    tmp = test_strings.second;
+    z = std::move(tmp);
+    ASSERT_EQ(std::string(z), test_strings.second);
+  }
+  {
+    // Test that self-move assignment doesn't crash/leak.
+    // Do not write such code!
+    absl::Cord my_small_cord("foo");
+    absl::Cord my_big_cord("loooooong coooooord");
+    // Bypass clang's warning on self move-assignment.
+    absl::Cord* my_small_alias =
+        my_unique_true_boolean ? &my_small_cord : &my_big_cord;
+    absl::Cord* my_big_alias =
+        !my_unique_true_boolean ? &my_small_cord : &my_big_cord;
+
+    *my_small_alias = std::move(my_small_cord);
+    *my_big_alias = std::move(my_big_cord);
+    // my_small_cord and my_big_cord are in an unspecified but valid
+    // state, and will be correctly destroyed here.
+  }
+}
+
+TEST(Cord, StartsEndsWith) {
+  absl::Cord x(absl::string_view("abcde"));
+  absl::Cord empty("");
+
+  ASSERT_TRUE(x.StartsWith(absl::Cord("abcde")));
+  ASSERT_TRUE(x.StartsWith(absl::Cord("abc")));
+  ASSERT_TRUE(x.StartsWith(absl::Cord("")));
+  ASSERT_TRUE(empty.StartsWith(absl::Cord("")));
+  ASSERT_TRUE(x.EndsWith(absl::Cord("abcde")));
+  ASSERT_TRUE(x.EndsWith(absl::Cord("cde")));
+  ASSERT_TRUE(x.EndsWith(absl::Cord("")));
+  ASSERT_TRUE(empty.EndsWith(absl::Cord("")));
+
+  ASSERT_TRUE(!x.StartsWith(absl::Cord("xyz")));
+  ASSERT_TRUE(!empty.StartsWith(absl::Cord("xyz")));
+  ASSERT_TRUE(!x.EndsWith(absl::Cord("xyz")));
+  ASSERT_TRUE(!empty.EndsWith(absl::Cord("xyz")));
+
+  ASSERT_TRUE(x.StartsWith("abcde"));
+  ASSERT_TRUE(x.StartsWith("abc"));
+  ASSERT_TRUE(x.StartsWith(""));
+  ASSERT_TRUE(empty.StartsWith(""));
+  ASSERT_TRUE(x.EndsWith("abcde"));
+  ASSERT_TRUE(x.EndsWith("cde"));
+  ASSERT_TRUE(x.EndsWith(""));
+  ASSERT_TRUE(empty.EndsWith(""));
+
+  ASSERT_TRUE(!x.StartsWith("xyz"));
+  ASSERT_TRUE(!empty.StartsWith("xyz"));
+  ASSERT_TRUE(!x.EndsWith("xyz"));
+  ASSERT_TRUE(!empty.EndsWith("xyz"));
+}
+
+TEST(Cord, Subcord) {
+  RandomEngine rng(testing::GTEST_FLAG(random_seed));
+  const std::string s = RandomLowercaseString(&rng, 1024);
+
+  absl::Cord a;
+  AppendWithFragments(s, &rng, &a);
+  ASSERT_EQ(s.size(), a.size());
+
+  // Check subcords of a, from a variety of interesting points.
+  std::set<size_t> positions;
+  for (int i = 0; i <= 32; ++i) {
+    positions.insert(i);
+    positions.insert(i * 32 - 1);
+    positions.insert(i * 32);
+    positions.insert(i * 32 + 1);
+    positions.insert(a.size() - i);
+  }
+  positions.insert(237);
+  positions.insert(732);
+  for (size_t pos : positions) {
+    if (pos > a.size()) continue;
+    for (size_t end_pos : positions) {
+      if (end_pos < pos || end_pos > a.size()) continue;
+      absl::Cord sa = a.Subcord(pos, end_pos - pos);
+      EXPECT_EQ(absl::string_view(s).substr(pos, end_pos - pos),
+                std::string(sa))
+          << a;
+    }
+  }
+
+  // Do the same thing for an inline cord.
+  const std::string sh = "short";
+  absl::Cord c(sh);
+  for (size_t pos = 0; pos <= sh.size(); ++pos) {
+    for (size_t n = 0; n <= sh.size() - pos; ++n) {
+      absl::Cord sc = c.Subcord(pos, n);
+      EXPECT_EQ(sh.substr(pos, n), std::string(sc)) << c;
+    }
+  }
+
+  // Check subcords of subcords.
+  absl::Cord sa = a.Subcord(0, a.size());
+  std::string ss = s.substr(0, s.size());
+  while (sa.size() > 1) {
+    sa = sa.Subcord(1, sa.size() - 2);
+    ss = ss.substr(1, ss.size() - 2);
+    EXPECT_EQ(ss, std::string(sa)) << a;
+    if (HasFailure()) break;  // halt cascade
+  }
+
+  // It is OK to ask for too much.
+  sa = a.Subcord(0, a.size() + 1);
+  EXPECT_EQ(s, std::string(sa));
+
+  // It is OK to ask for something beyond the end.
+  sa = a.Subcord(a.size() + 1, 0);
+  EXPECT_TRUE(sa.empty());
+  sa = a.Subcord(a.size() + 1, 1);
+  EXPECT_TRUE(sa.empty());
+}
+
+TEST(Cord, Swap) {
+  absl::string_view a("Dexter");
+  absl::string_view b("Mandark");
+  absl::Cord x(a);
+  absl::Cord y(b);
+  swap(x, y);
+  ASSERT_EQ(x, absl::Cord(b));
+  ASSERT_EQ(y, absl::Cord(a));
+}
+
+static void VerifyCopyToString(const absl::Cord& cord) {
+  std::string initially_empty;
+  absl::CopyCordToString(cord, &initially_empty);
+  EXPECT_EQ(initially_empty, cord);
+
+  constexpr size_t kInitialLength = 1024;
+  std::string has_initial_contents(kInitialLength, 'x');
+  const char* address_before_copy = has_initial_contents.data();
+  absl::CopyCordToString(cord, &has_initial_contents);
+  EXPECT_EQ(has_initial_contents, cord);
+
+  if (cord.size() <= kInitialLength) {
+    EXPECT_EQ(has_initial_contents.data(), address_before_copy)
+        << "CopyCordToString allocated new std::string storage; "
+           "has_initial_contents = \""
+        << has_initial_contents << "\"";
+  }
+}
+
+TEST(Cord, CopyToString) {
+  VerifyCopyToString(absl::Cord());
+  VerifyCopyToString(absl::Cord("small cord"));
+  VerifyCopyToString(
+      absl::MakeFragmentedCord({"fragmented ", "cord ", "to ", "test ",
+                                "copying ", "to ", "a ", "string."}));
+}
+
+static bool IsFlat(const absl::Cord& c) {
+  return c.chunk_begin() == c.chunk_end() || ++c.chunk_begin() == c.chunk_end();
+}
+
+static void VerifyFlatten(absl::Cord c) {
+  std::string old_contents(c);
+  absl::string_view old_flat;
+  bool already_flat_and_non_empty = IsFlat(c) && !c.empty();
+  if (already_flat_and_non_empty) {
+    old_flat = *c.chunk_begin();
+  }
+  absl::string_view new_flat = c.Flatten();
+
+  // Verify that the contents of the flattened Cord are correct.
+  EXPECT_EQ(new_flat, old_contents);
+  EXPECT_EQ(std::string(c), old_contents);
+
+  // If the Cord contained data and was already flat, verify that the data
+  // wasn't copied.
+  if (already_flat_and_non_empty) {
+    EXPECT_EQ(old_flat.data(), new_flat.data())
+        << "Allocated new memory even though the Cord was already flat.";
+  }
+
+  // Verify that the flattened Cord is in fact flat.
+  EXPECT_TRUE(IsFlat(c));
+}
+
+TEST(Cord, Flatten) {
+  VerifyFlatten(absl::Cord());
+  VerifyFlatten(absl::Cord("small cord"));
+  VerifyFlatten(absl::Cord("larger than small buffer optimization"));
+  VerifyFlatten(absl::MakeFragmentedCord({"small ", "fragmented ", "cord"}));
+
+  // Test with a cord that is longer than the largest flat buffer
+  RandomEngine rng(testing::GTEST_FLAG(random_seed));
+  VerifyFlatten(absl::Cord(RandomLowercaseString(&rng, 8192)));
+}
+
+// Test data
+namespace {
+class TestData {
+ private:
+  std::vector<std::string> data_;
+
+  // Return a std::string of the specified length.
+  static std::string MakeString(int length) {
+    std::string result;
+    char buf[30];
+    snprintf(buf, sizeof(buf), "(%d)", length);
+    while (result.size() < length) {
+      result += buf;
+    }
+    result.resize(length);
+    return result;
+  }
+
+ public:
+  TestData() {
+    // short strings increasing in length by one
+    for (int i = 0; i < 30; i++) {
+      data_.push_back(MakeString(i));
+    }
+
+    // strings around half kMaxFlatLength
+    static const int kMaxFlatLength = 4096 - 9;
+    static const int kHalf = kMaxFlatLength / 2;
+
+    for (int i = -10; i <= +10; i++) {
+      data_.push_back(MakeString(kHalf + i));
+    }
+
+    for (int i = -10; i <= +10; i++) {
+      data_.push_back(MakeString(kMaxFlatLength + i));
+    }
+  }
+
+  size_t size() const { return data_.size(); }
+  const std::string& data(size_t i) const { return data_[i]; }
+};
+}  // namespace
+
+TEST(Cord, MultipleLengths) {
+  TestData d;
+  for (size_t i = 0; i < d.size(); i++) {
+    std::string a = d.data(i);
+
+    { // Construct from Cord
+      absl::Cord tmp(a);
+      absl::Cord x(tmp);
+      EXPECT_EQ(a, std::string(x)) << "'" << a << "'";
+    }
+
+    { // Construct from absl::string_view
+      absl::Cord x(a);
+      EXPECT_EQ(a, std::string(x)) << "'" << a << "'";
+    }
+
+    { // Append cord to self
+      absl::Cord self(a);
+      self.Append(self);
+      EXPECT_EQ(a + a, std::string(self)) << "'" << a << "' + '" << a << "'";
+    }
+
+    { // Prepend cord to self
+      absl::Cord self(a);
+      self.Prepend(self);
+      EXPECT_EQ(a + a, std::string(self)) << "'" << a << "' + '" << a << "'";
+    }
+
+    // Try to append/prepend others
+    for (size_t j = 0; j < d.size(); j++) {
+      std::string b = d.data(j);
+
+      { // CopyFrom Cord
+        absl::Cord x(a);
+        absl::Cord y(b);
+        x = y;
+        EXPECT_EQ(b, std::string(x)) << "'" << a << "' + '" << b << "'";
+      }
+
+      { // CopyFrom absl::string_view
+        absl::Cord x(a);
+        x = b;
+        EXPECT_EQ(b, std::string(x)) << "'" << a << "' + '" << b << "'";
+      }
+
+      { // Cord::Append(Cord)
+        absl::Cord x(a);
+        absl::Cord y(b);
+        x.Append(y);
+        EXPECT_EQ(a + b, std::string(x)) << "'" << a << "' + '" << b << "'";
+      }
+
+      { // Cord::Append(absl::string_view)
+        absl::Cord x(a);
+        x.Append(b);
+        EXPECT_EQ(a + b, std::string(x)) << "'" << a << "' + '" << b << "'";
+      }
+
+      { // Cord::Prepend(Cord)
+        absl::Cord x(a);
+        absl::Cord y(b);
+        x.Prepend(y);
+        EXPECT_EQ(b + a, std::string(x)) << "'" << b << "' + '" << a << "'";
+      }
+
+      { // Cord::Prepend(absl::string_view)
+        absl::Cord x(a);
+        x.Prepend(b);
+        EXPECT_EQ(b + a, std::string(x)) << "'" << b << "' + '" << a << "'";
+      }
+    }
+  }
+}
+
+namespace {
+
+TEST(Cord, RemoveSuffixWithExternalOrSubstring) {
+  absl::Cord cord = absl::MakeCordFromExternal(
+      "foo bar baz", [](absl::string_view s) { DoNothing(s, nullptr); });
+
+  EXPECT_EQ("foo bar baz", std::string(cord));
+
+  // This RemoveSuffix() will wrap the EXTERNAL node in a SUBSTRING node.
+  cord.RemoveSuffix(4);
+  EXPECT_EQ("foo bar", std::string(cord));
+
+  // This RemoveSuffix() will adjust the SUBSTRING node in-place.
+  cord.RemoveSuffix(4);
+  EXPECT_EQ("foo", std::string(cord));
+}
+
+TEST(Cord, RemoveSuffixMakesZeroLengthNode) {
+  absl::Cord c;
+  c.Append(absl::Cord(std::string(100, 'x')));
+  absl::Cord other_ref = c;  // Prevent inplace appends
+  c.Append(absl::Cord(std::string(200, 'y')));
+  c.RemoveSuffix(200);
+  EXPECT_EQ(std::string(100, 'x'), std::string(c));
+}
+
+}  // namespace
+
+// CordSpliceTest contributed by hendrie.
+namespace {
+
+// Create a cord with an external memory block filled with 'z'
+absl::Cord CordWithZedBlock(size_t size) {
+  char* data = new char[size];
+  if (size > 0) {
+    memset(data, 'z', size);
+  }
+  absl::Cord cord = absl::MakeCordFromExternal(
+      absl::string_view(data, size),
+      [](absl::string_view s) { delete[] s.data(); });
+  return cord;
+}
+
+// Establish that ZedBlock does what we think it does.
+TEST(CordSpliceTest, ZedBlock) {
+  absl::Cord blob = CordWithZedBlock(10);
+  EXPECT_EQ(10, blob.size());
+  std::string s;
+  absl::CopyCordToString(blob, &s);
+  EXPECT_EQ("zzzzzzzzzz", s);
+}
+
+TEST(CordSpliceTest, ZedBlock0) {
+  absl::Cord blob = CordWithZedBlock(0);
+  EXPECT_EQ(0, blob.size());
+  std::string s;
+  absl::CopyCordToString(blob, &s);
+  EXPECT_EQ("", s);
+}
+
+TEST(CordSpliceTest, ZedBlockSuffix1) {
+  absl::Cord blob = CordWithZedBlock(10);
+  EXPECT_EQ(10, blob.size());
+  absl::Cord suffix(blob);
+  suffix.RemovePrefix(9);
+  EXPECT_EQ(1, suffix.size());
+  std::string s;
+  absl::CopyCordToString(suffix, &s);
+  EXPECT_EQ("z", s);
+}
+
+// Remove all of a prefix block
+TEST(CordSpliceTest, ZedBlockSuffix0) {
+  absl::Cord blob = CordWithZedBlock(10);
+  EXPECT_EQ(10, blob.size());
+  absl::Cord suffix(blob);
+  suffix.RemovePrefix(10);
+  EXPECT_EQ(0, suffix.size());
+  std::string s;
+  absl::CopyCordToString(suffix, &s);
+  EXPECT_EQ("", s);
+}
+
+absl::Cord BigCord(size_t len, char v) {
+  std::string s(len, v);
+  return absl::Cord(s);
+}
+
+// Splice block into cord.
+absl::Cord SpliceCord(const absl::Cord& blob, int64_t offset,
+                      const absl::Cord& block) {
+  ABSL_RAW_CHECK(offset >= 0, "");
+  ABSL_RAW_CHECK(offset + block.size() <= blob.size(), "");
+  absl::Cord result(blob);
+  result.RemoveSuffix(blob.size() - offset);
+  result.Append(block);
+  absl::Cord suffix(blob);
+  suffix.RemovePrefix(offset + block.size());
+  result.Append(suffix);
+  ABSL_RAW_CHECK(blob.size() == result.size(), "");
+  return result;
+}
+
+// Taking an empty suffix of a block breaks appending.
+TEST(CordSpliceTest, RemoveEntireBlock1) {
+  absl::Cord zero = CordWithZedBlock(10);
+  absl::Cord suffix(zero);
+  suffix.RemovePrefix(10);
+  absl::Cord result;
+  result.Append(suffix);
+}
+
+TEST(CordSpliceTest, RemoveEntireBlock2) {
+  absl::Cord zero = CordWithZedBlock(10);
+  absl::Cord prefix(zero);
+  prefix.RemoveSuffix(10);
+  absl::Cord suffix(zero);
+  suffix.RemovePrefix(10);
+  absl::Cord result(prefix);
+  result.Append(suffix);
+}
+
+TEST(CordSpliceTest, RemoveEntireBlock3) {
+  absl::Cord blob = CordWithZedBlock(10);
+  absl::Cord block = BigCord(10, 'b');
+  blob = SpliceCord(blob, 0, block);
+}
+
+struct CordCompareTestCase {
+  template <typename LHS, typename RHS>
+  CordCompareTestCase(const LHS& lhs, const RHS& rhs)
+      : lhs_cord(lhs), rhs_cord(rhs) {}
+
+  absl::Cord lhs_cord;
+  absl::Cord rhs_cord;
+};
+
+const auto sign = [](int x) { return x == 0 ? 0 : (x > 0 ? 1 : -1); };
+
+void VerifyComparison(const CordCompareTestCase& test_case) {
+  std::string lhs_string(test_case.lhs_cord);
+  std::string rhs_string(test_case.rhs_cord);
+  int expected = sign(lhs_string.compare(rhs_string));
+  EXPECT_EQ(expected, test_case.lhs_cord.Compare(test_case.rhs_cord))
+      << "LHS=" << lhs_string << "; RHS=" << rhs_string;
+  EXPECT_EQ(expected, test_case.lhs_cord.Compare(rhs_string))
+      << "LHS=" << lhs_string << "; RHS=" << rhs_string;
+  EXPECT_EQ(-expected, test_case.rhs_cord.Compare(test_case.lhs_cord))
+      << "LHS=" << rhs_string << "; RHS=" << lhs_string;
+  EXPECT_EQ(-expected, test_case.rhs_cord.Compare(lhs_string))
+      << "LHS=" << rhs_string << "; RHS=" << lhs_string;
+}
+
+TEST(Cord, Compare) {
+  absl::Cord subcord("aaaaaBBBBBcccccDDDDD");
+  subcord = subcord.Subcord(3, 10);
+
+  absl::Cord tmp("aaaaaaaaaaaaaaaa");
+  tmp.Append("BBBBBBBBBBBBBBBB");
+  absl::Cord concat = absl::Cord("cccccccccccccccc");
+  concat.Append("DDDDDDDDDDDDDDDD");
+  concat.Prepend(tmp);
+
+  absl::Cord concat2("aaaaaaaaaaaaa");
+  concat2.Append("aaaBBBBBBBBBBBBBBBBccccc");
+  concat2.Append("cccccccccccDDDDDDDDDDDDDD");
+  concat2.Append("DD");
+
+  std::vector<CordCompareTestCase> test_cases = {{
+      // Inline cords
+      {"abcdef", "abcdef"},
+      {"abcdef", "abcdee"},
+      {"abcdef", "abcdeg"},
+      {"bbcdef", "abcdef"},
+      {"bbcdef", "abcdeg"},
+      {"abcdefa", "abcdef"},
+      {"abcdef", "abcdefa"},
+
+      // Small flat cords
+      {"aaaaaBBBBBcccccDDDDD", "aaaaaBBBBBcccccDDDDD"},
+      {"aaaaaBBBBBcccccDDDDD", "aaaaaBBBBBxccccDDDDD"},
+      {"aaaaaBBBBBcxcccDDDDD", "aaaaaBBBBBcccccDDDDD"},
+      {"aaaaaBBBBBxccccDDDDD", "aaaaaBBBBBcccccDDDDX"},
+      {"aaaaaBBBBBcccccDDDDDa", "aaaaaBBBBBcccccDDDDD"},
+      {"aaaaaBBBBBcccccDDDDD", "aaaaaBBBBBcccccDDDDDa"},
+
+      // Subcords
+      {subcord, subcord},
+      {subcord, "aaBBBBBccc"},
+      {subcord, "aaBBBBBccd"},
+      {subcord, "aaBBBBBccb"},
+      {subcord, "aaBBBBBxcb"},
+      {subcord, "aaBBBBBccca"},
+      {subcord, "aaBBBBBcc"},
+
+      // Concats
+      {concat, concat},
+      {concat,
+       "aaaaaaaaaaaaaaaaBBBBBBBBBBBBBBBBccccccccccccccccDDDDDDDDDDDDDDDD"},
+      {concat,
+       "aaaaaaaaaaaaaaaaBBBBBBBBBBBBBBBBcccccccccccccccxDDDDDDDDDDDDDDDD"},
+      {concat,
+       "aaaaaaaaaaaaaaaaBBBBBBBBBBBBBBBBacccccccccccccccDDDDDDDDDDDDDDDD"},
+      {concat,
+       "aaaaaaaaaaaaaaaaBBBBBBBBBBBBBBBBccccccccccccccccDDDDDDDDDDDDDDD"},
+      {concat,
+       "aaaaaaaaaaaaaaaaBBBBBBBBBBBBBBBBccccccccccccccccDDDDDDDDDDDDDDDDe"},
+
+      {concat, concat2},
+  }};
+
+  for (const auto& tc : test_cases) {
+    VerifyComparison(tc);
+  }
+}
+
+TEST(Cord, CompareAfterAssign) {
+  absl::Cord a("aaaaaa1111111");
+  absl::Cord b("aaaaaa2222222");
+  a = "cccccc";
+  b = "cccccc";
+  EXPECT_EQ(a, b);
+  EXPECT_FALSE(a < b);
+
+  a = "aaaa";
+  b = "bbbbb";
+  a = "";
+  b = "";
+  EXPECT_EQ(a, b);
+  EXPECT_FALSE(a < b);
+}
+
+// Test CompareTo() and ComparePrefix() against string and substring
+// comparison methods from std::basic_string.
+static void TestCompare(const absl::Cord& c, const absl::Cord& d,
+                        RandomEngine* rng) {
+  typedef std::basic_string<uint8_t> ustring;
+  ustring cs(reinterpret_cast<const uint8_t*>(std::string(c).data()), c.size());
+  ustring ds(reinterpret_cast<const uint8_t*>(std::string(d).data()), d.size());
+  // ustring comparison is ideal because we expect Cord comparisons to be
+  // based on unsigned byte comparisons regardless of whether char is signed.
+  int expected = sign(cs.compare(ds));
+  EXPECT_EQ(expected, sign(c.Compare(d))) << c << ", " << d;
+}
+
+TEST(Compare, ComparisonIsUnsigned) {
+  RandomEngine rng(testing::GTEST_FLAG(random_seed));
+  std::uniform_int_distribution<uint32_t> uniform_uint8(0, 255);
+  char x = static_cast<char>(uniform_uint8(rng));
+  TestCompare(
+      absl::Cord(std::string(GetUniformRandomUpTo(&rng, 100), x)),
+      absl::Cord(std::string(GetUniformRandomUpTo(&rng, 100), x ^ 0x80)), &rng);
+}
+
+TEST(Compare, RandomComparisons) {
+  const int kIters = 5000;
+  RandomEngine rng(testing::GTEST_FLAG(random_seed));
+
+  int n = GetUniformRandomUpTo(&rng, 5000);
+  absl::Cord a[] = {MakeExternalCord(n),
+                    absl::Cord("ant"),
+                    absl::Cord("elephant"),
+                    absl::Cord("giraffe"),
+                    absl::Cord(std::string(GetUniformRandomUpTo(&rng, 100),
+                                           GetUniformRandomUpTo(&rng, 100))),
+                    absl::Cord(""),
+                    absl::Cord("x"),
+                    absl::Cord("A"),
+                    absl::Cord("B"),
+                    absl::Cord("C")};
+  for (int i = 0; i < kIters; i++) {
+    absl::Cord c, d;
+    for (int j = 0; j < (i % 7) + 1; j++) {
+      c.Append(a[GetUniformRandomUpTo(&rng, ABSL_ARRAYSIZE(a))]);
+      d.Append(a[GetUniformRandomUpTo(&rng, ABSL_ARRAYSIZE(a))]);
+    }
+    std::bernoulli_distribution coin_flip(0.5);
+    TestCompare(coin_flip(rng) ? c : absl::Cord(std::string(c)),
+                coin_flip(rng) ? d : absl::Cord(std::string(d)), &rng);
+  }
+}
+
+template <typename T1, typename T2>
+void CompareOperators() {
+  const T1 a("a");
+  const T2 b("b");
+
+  EXPECT_TRUE(a == a);
+  // For pointer type (i.e. `const char*`), operator== compares the address
+  // instead of the std::string, so `a == const char*("a")` isn't necessarily true.
+  EXPECT_TRUE(std::is_pointer<T1>::value || a == T1("a"));
+  EXPECT_TRUE(std::is_pointer<T2>::value || a == T2("a"));
+  EXPECT_FALSE(a == b);
+
+  EXPECT_TRUE(a != b);
+  EXPECT_FALSE(a != a);
+
+  EXPECT_TRUE(a < b);
+  EXPECT_FALSE(b < a);
+
+  EXPECT_TRUE(b > a);
+  EXPECT_FALSE(a > b);
+
+  EXPECT_TRUE(a >= a);
+  EXPECT_TRUE(b >= a);
+  EXPECT_FALSE(a >= b);
+
+  EXPECT_TRUE(a <= a);
+  EXPECT_TRUE(a <= b);
+  EXPECT_FALSE(b <= a);
+}
+
+TEST(ComparisonOperators, Cord_Cord) {
+  CompareOperators<absl::Cord, absl::Cord>();
+}
+
+TEST(ComparisonOperators, Cord_StringPiece) {
+  CompareOperators<absl::Cord, absl::string_view>();
+}
+
+TEST(ComparisonOperators, StringPiece_Cord) {
+  CompareOperators<absl::string_view, absl::Cord>();
+}
+
+TEST(ComparisonOperators, Cord_string) {
+  CompareOperators<absl::Cord, std::string>();
+}
+
+TEST(ComparisonOperators, string_Cord) {
+  CompareOperators<std::string, absl::Cord>();
+}
+
+TEST(ComparisonOperators, stdstring_Cord) {
+  CompareOperators<std::string, absl::Cord>();
+}
+
+TEST(ComparisonOperators, Cord_stdstring) {
+  CompareOperators<absl::Cord, std::string>();
+}
+
+TEST(ComparisonOperators, charstar_Cord) {
+  CompareOperators<const char*, absl::Cord>();
+}
+
+TEST(ComparisonOperators, Cord_charstar) {
+  CompareOperators<absl::Cord, const char*>();
+}
+
+TEST(ConstructFromExternal, ReleaserInvoked) {
+  // Empty external memory means the releaser should be called immediately.
+  {
+    bool invoked = false;
+    auto releaser = [&invoked](absl::string_view) { invoked = true; };
+    {
+      auto c = absl::MakeCordFromExternal("", releaser);
+      EXPECT_TRUE(invoked);
+    }
+  }
+
+  // If the size of the data is small enough, a future constructor
+  // implementation may copy the bytes and immediately invoke the releaser
+  // instead of creating an external node. We make a large dummy std::string to
+  // make this test independent of such an optimization.
+  std::string large_dummy(2048, 'c');
+  {
+    bool invoked = false;
+    auto releaser = [&invoked](absl::string_view) { invoked = true; };
+    {
+      auto c = absl::MakeCordFromExternal(large_dummy, releaser);
+      EXPECT_FALSE(invoked);
+    }
+    EXPECT_TRUE(invoked);
+  }
+
+  {
+    bool invoked = false;
+    auto releaser = [&invoked](absl::string_view) { invoked = true; };
+    {
+      absl::Cord copy;
+      {
+        auto c = absl::MakeCordFromExternal(large_dummy, releaser);
+        copy = c;
+        EXPECT_FALSE(invoked);
+      }
+      EXPECT_FALSE(invoked);
+    }
+    EXPECT_TRUE(invoked);
+  }
+}
+
+TEST(ConstructFromExternal, CompareContents) {
+  RandomEngine rng(testing::GTEST_FLAG(random_seed));
+
+  for (int length = 1; length <= 2048; length *= 2) {
+    std::string data = RandomLowercaseString(&rng, length);
+    auto* external = new std::string(data);
+    auto cord =
+        absl::MakeCordFromExternal(*external, [external](absl::string_view sv) {
+          EXPECT_EQ(external->data(), sv.data());
+          EXPECT_EQ(external->size(), sv.size());
+          delete external;
+        });
+    EXPECT_EQ(data, cord);
+  }
+}
+
+TEST(ConstructFromExternal, LargeReleaser) {
+  RandomEngine rng(testing::GTEST_FLAG(random_seed));
+  constexpr size_t kLength = 256;
+  std::string data = RandomLowercaseString(&rng, kLength);
+  std::array<char, kLength> data_array;
+  for (size_t i = 0; i < kLength; ++i) data_array[i] = data[i];
+  bool invoked = false;
+  auto releaser = [data_array, &invoked](absl::string_view data) {
+    EXPECT_EQ(data, absl::string_view(data_array.data(), data_array.size()));
+    invoked = true;
+  };
+  (void)absl::MakeCordFromExternal(data, releaser);
+  EXPECT_TRUE(invoked);
+}
+
+TEST(ConstructFromExternal, FunctionPointerReleaser) {
+  static absl::string_view data("hello world");
+  static bool invoked;
+  auto* releaser =
+      static_cast<void (*)(absl::string_view)>([](absl::string_view sv) {
+        EXPECT_EQ(data, sv);
+        invoked = true;
+      });
+  invoked = false;
+  (void)absl::MakeCordFromExternal(data, releaser);
+  EXPECT_TRUE(invoked);
+
+  invoked = false;
+  (void)absl::MakeCordFromExternal(data, *releaser);
+  EXPECT_TRUE(invoked);
+}
+
+TEST(ConstructFromExternal, MoveOnlyReleaser) {
+  struct Releaser {
+    explicit Releaser(bool* invoked) : invoked(invoked) {}
+    Releaser(Releaser&& other) noexcept : invoked(other.invoked) {}
+    void operator()(absl::string_view) const { *invoked = true; }
+
+    bool* invoked;
+  };
+
+  bool invoked = false;
+  (void)absl::MakeCordFromExternal("dummy", Releaser(&invoked));
+  EXPECT_TRUE(invoked);
+}
+
+TEST(ConstructFromExternal, NonTrivialReleaserDestructor) {
+  struct Releaser {
+    explicit Releaser(bool* destroyed) : destroyed(destroyed) {}
+    ~Releaser() { *destroyed = true; }
+    void operator()(absl::string_view) const {}
+
+    bool* destroyed;
+  };
+
+  bool destroyed = false;
+  Releaser releaser(&destroyed);
+  (void)absl::MakeCordFromExternal("dummy", releaser);
+  EXPECT_TRUE(destroyed);
+}
+
+TEST(ConstructFromExternal, ReferenceQualifierOverloads) {
+  struct Releaser {
+    void operator()(absl::string_view) & { *lvalue_invoked = true; }
+    void operator()(absl::string_view) && { *rvalue_invoked = true; }
+
+    bool* lvalue_invoked;
+    bool* rvalue_invoked;
+  };
+
+  bool lvalue_invoked = false;
+  bool rvalue_invoked = false;
+  Releaser releaser = {&lvalue_invoked, &rvalue_invoked};
+  (void)absl::MakeCordFromExternal("", releaser);
+  EXPECT_FALSE(lvalue_invoked);
+  EXPECT_TRUE(rvalue_invoked);
+  rvalue_invoked = false;
+
+  (void)absl::MakeCordFromExternal("dummy", releaser);
+  EXPECT_FALSE(lvalue_invoked);
+  EXPECT_TRUE(rvalue_invoked);
+  rvalue_invoked = false;
+
+  // NOLINTNEXTLINE: suppress clang-tidy std::move on trivially copyable type.
+  (void)absl::MakeCordFromExternal("dummy", std::move(releaser));
+  EXPECT_FALSE(lvalue_invoked);
+  EXPECT_TRUE(rvalue_invoked);
+}
+
+TEST(ExternalMemory, BasicUsage) {
+  static const char* strings[] = { "", "hello", "there" };
+  for (const char* str : strings) {
+    absl::Cord dst("(prefix)");
+    AddExternalMemory(str, &dst);
+    dst.Append("(suffix)");
+    EXPECT_EQ((std::string("(prefix)") + str + std::string("(suffix)")),
+              std::string(dst));
+  }
+}
+
+TEST(ExternalMemory, RemovePrefixSuffix) {
+  // Exhaustively try all sub-strings.
+  absl::Cord cord = MakeComposite();
+  std::string s = std::string(cord);
+  for (int offset = 0; offset <= s.size(); offset++) {
+    for (int length = 0; length <= s.size() - offset; length++) {
+      absl::Cord result(cord);
+      result.RemovePrefix(offset);
+      result.RemoveSuffix(result.size() - length);
+      EXPECT_EQ(s.substr(offset, length), std::string(result))
+          << offset << " " << length;
+    }
+  }
+}
+
+TEST(ExternalMemory, Get) {
+  absl::Cord cord("hello");
+  AddExternalMemory(" world!", &cord);
+  AddExternalMemory(" how are ", &cord);
+  cord.Append(" you?");
+  std::string s = std::string(cord);
+  for (int i = 0; i < s.size(); i++) {
+    EXPECT_EQ(s[i], cord[i]);
+  }
+}
+
+// CordMemoryUsage tests verify the correctness of the EstimatedMemoryUsage()
+// These tests take into account that the reported memory usage is approximate
+// and non-deterministic. For all tests, We verify that the reported memory
+// usage is larger than `size()`, and less than `size() * 1.5` as a cord should
+// never reserve more 'extra' capacity than half of its size as it grows.
+// Additionally we have some whiteboxed expectations based on our knowledge of
+// the layout and size of empty and inlined cords, and flat nodes.
+
+TEST(CordMemoryUsage, Empty) {
+  EXPECT_EQ(sizeof(absl::Cord), absl::Cord().EstimatedMemoryUsage());
+}
+
+TEST(CordMemoryUsage, Embedded) {
+  absl::Cord a("hello");
+  EXPECT_EQ(a.EstimatedMemoryUsage(), sizeof(absl::Cord));
+}
+
+TEST(CordMemoryUsage, EmbeddedAppend) {
+  absl::Cord a("a");
+  absl::Cord b("bcd");
+  EXPECT_EQ(b.EstimatedMemoryUsage(), sizeof(absl::Cord));
+  a.Append(b);
+  EXPECT_EQ(a.EstimatedMemoryUsage(), sizeof(absl::Cord));
+}
+
+TEST(CordMemoryUsage, ExternalMemory) {
+  static const int kLength = 1000;
+  absl::Cord cord;
+  AddExternalMemory(std::string(kLength, 'x'), &cord);
+  EXPECT_GT(cord.EstimatedMemoryUsage(), kLength);
+  EXPECT_LE(cord.EstimatedMemoryUsage(), kLength * 1.5);
+}
+
+TEST(CordMemoryUsage, Flat) {
+  static const int kLength = 125;
+  absl::Cord a(std::string(kLength, 'a'));
+  EXPECT_GT(a.EstimatedMemoryUsage(), kLength);
+  EXPECT_LE(a.EstimatedMemoryUsage(), kLength * 1.5);
+}
+
+TEST(CordMemoryUsage, AppendFlat) {
+  using absl::strings_internal::CordTestAccess;
+  absl::Cord a(std::string(CordTestAccess::MaxFlatLength(), 'a'));
+  size_t length = a.EstimatedMemoryUsage();
+  a.Append(std::string(CordTestAccess::MaxFlatLength(), 'b'));
+  size_t delta = a.EstimatedMemoryUsage() - length;
+  EXPECT_GT(delta, CordTestAccess::MaxFlatLength());
+  EXPECT_LE(delta, CordTestAccess::MaxFlatLength() * 1.5);
+}
+
+// Regtest for a change that had to be rolled back because it expanded out
+// of the InlineRep too soon, which was observable through MemoryUsage().
+TEST(CordMemoryUsage, InlineRep) {
+  constexpr size_t kMaxInline = 15;  // Cord::InlineRep::N
+  const std::string small_string(kMaxInline, 'x');
+  absl::Cord c1(small_string);
+
+  absl::Cord c2;
+  c2.Append(small_string);
+  EXPECT_EQ(c1, c2);
+  EXPECT_EQ(c1.EstimatedMemoryUsage(), c2.EstimatedMemoryUsage());
+}
+
+}  // namespace
+
+// Regtest for 7510292 (fix a bug introduced by 7465150)
+TEST(Cord, Concat_Append) {
+  // Create a rep of type CONCAT
+  absl::Cord s1("foobarbarbarbarbar");
+  s1.Append("abcdefgabcdefgabcdefgabcdefgabcdefgabcdefgabcdefg");
+  size_t size = s1.size();
+
+  // Create a copy of s1 and append to it.
+  absl::Cord s2 = s1;
+  s2.Append("x");
+
+  // 7465150 modifies s1 when it shouldn't.
+  EXPECT_EQ(s1.size(), size);
+  EXPECT_EQ(s2.size(), size + 1);
+}
+
+TEST(MakeFragmentedCord, MakeFragmentedCordFromInitializerList) {
+  absl::Cord fragmented =
+      absl::MakeFragmentedCord({"A ", "fragmented ", "Cord"});
+
+  EXPECT_EQ("A fragmented Cord", fragmented);
+
+  auto chunk_it = fragmented.chunk_begin();
+
+  ASSERT_TRUE(chunk_it != fragmented.chunk_end());
+  EXPECT_EQ("A ", *chunk_it);
+
+  ASSERT_TRUE(++chunk_it != fragmented.chunk_end());
+  EXPECT_EQ("fragmented ", *chunk_it);
+
+  ASSERT_TRUE(++chunk_it != fragmented.chunk_end());
+  EXPECT_EQ("Cord", *chunk_it);
+
+  ASSERT_TRUE(++chunk_it == fragmented.chunk_end());
+}
+
+TEST(MakeFragmentedCord, MakeFragmentedCordFromVector) {
+  std::vector<absl::string_view> chunks = {"A ", "fragmented ", "Cord"};
+  absl::Cord fragmented = absl::MakeFragmentedCord(chunks);
+
+  EXPECT_EQ("A fragmented Cord", fragmented);
+
+  auto chunk_it = fragmented.chunk_begin();
+
+  ASSERT_TRUE(chunk_it != fragmented.chunk_end());
+  EXPECT_EQ("A ", *chunk_it);
+
+  ASSERT_TRUE(++chunk_it != fragmented.chunk_end());
+  EXPECT_EQ("fragmented ", *chunk_it);
+
+  ASSERT_TRUE(++chunk_it != fragmented.chunk_end());
+  EXPECT_EQ("Cord", *chunk_it);
+
+  ASSERT_TRUE(++chunk_it == fragmented.chunk_end());
+}
+
+TEST(CordChunkIterator, Traits) {
+  static_assert(std::is_copy_constructible<absl::Cord::ChunkIterator>::value,
+                "");
+  static_assert(std::is_copy_assignable<absl::Cord::ChunkIterator>::value, "");
+
+  // Move semantics to satisfy swappable via std::swap
+  static_assert(std::is_move_constructible<absl::Cord::ChunkIterator>::value,
+                "");
+  static_assert(std::is_move_assignable<absl::Cord::ChunkIterator>::value, "");
+
+  static_assert(
+      std::is_same<
+          std::iterator_traits<absl::Cord::ChunkIterator>::iterator_category,
+          std::input_iterator_tag>::value,
+      "");
+  static_assert(
+      std::is_same<std::iterator_traits<absl::Cord::ChunkIterator>::value_type,
+                   absl::string_view>::value,
+      "");
+  static_assert(
+      std::is_same<
+          std::iterator_traits<absl::Cord::ChunkIterator>::difference_type,
+          ptrdiff_t>::value,
+      "");
+  static_assert(
+      std::is_same<std::iterator_traits<absl::Cord::ChunkIterator>::pointer,
+                   const absl::string_view*>::value,
+      "");
+  static_assert(
+      std::is_same<std::iterator_traits<absl::Cord::ChunkIterator>::reference,
+                   absl::string_view>::value,
+      "");
+}
+
+static void VerifyChunkIterator(const absl::Cord& cord,
+                                size_t expected_chunks) {
+  EXPECT_EQ(cord.chunk_begin() == cord.chunk_end(), cord.empty()) << cord;
+  EXPECT_EQ(cord.chunk_begin() != cord.chunk_end(), !cord.empty());
+
+  absl::Cord::ChunkRange range = cord.Chunks();
+  EXPECT_EQ(range.begin() == range.end(), cord.empty());
+  EXPECT_EQ(range.begin() != range.end(), !cord.empty());
+
+  std::string content(cord);
+  size_t pos = 0;
+  auto pre_iter = cord.chunk_begin(), post_iter = cord.chunk_begin();
+  size_t n_chunks = 0;
+  while (pre_iter != cord.chunk_end() && post_iter != cord.chunk_end()) {
+    EXPECT_FALSE(pre_iter == cord.chunk_end());   // NOLINT: explicitly test ==
+    EXPECT_FALSE(post_iter == cord.chunk_end());  // NOLINT
+
+    EXPECT_EQ(pre_iter, post_iter);
+    EXPECT_EQ(*pre_iter, *post_iter);
+
+    EXPECT_EQ(pre_iter->data(), (*pre_iter).data());
+    EXPECT_EQ(pre_iter->size(), (*pre_iter).size());
+
+    absl::string_view chunk = *pre_iter;
+    EXPECT_FALSE(chunk.empty());
+    EXPECT_LE(pos + chunk.size(), content.size());
+    EXPECT_EQ(absl::string_view(content.c_str() + pos, chunk.size()), chunk);
+
+    int n_equal_iterators = 0;
+    for (absl::Cord::ChunkIterator it = range.begin(); it != range.end();
+         ++it) {
+      n_equal_iterators += static_cast<int>(it == pre_iter);
+    }
+    EXPECT_EQ(n_equal_iterators, 1);
+
+    ++pre_iter;
+    EXPECT_EQ(*post_iter++, chunk);
+
+    pos += chunk.size();
+    ++n_chunks;
+  }
+  EXPECT_EQ(expected_chunks, n_chunks);
+  EXPECT_EQ(pos, content.size());
+  EXPECT_TRUE(pre_iter == cord.chunk_end());   // NOLINT: explicitly test ==
+  EXPECT_TRUE(post_iter == cord.chunk_end());  // NOLINT
+}
+
+TEST(CordChunkIterator, Operations) {
+  absl::Cord empty_cord;
+  VerifyChunkIterator(empty_cord, 0);
+
+  absl::Cord small_buffer_cord("small cord");
+  VerifyChunkIterator(small_buffer_cord, 1);
+
+  absl::Cord flat_node_cord("larger than small buffer optimization");
+  VerifyChunkIterator(flat_node_cord, 1);
+
+  VerifyChunkIterator(
+      absl::MakeFragmentedCord({"a ", "small ", "fragmented ", "cord ", "for ",
+                                "testing ", "chunk ", "iterations."}),
+      8);
+
+  absl::Cord reused_nodes_cord(std::string(40, 'c'));
+  reused_nodes_cord.Prepend(absl::Cord(std::string(40, 'b')));
+  reused_nodes_cord.Prepend(absl::Cord(std::string(40, 'a')));
+  size_t expected_chunks = 3;
+  for (int i = 0; i < 8; ++i) {
+    reused_nodes_cord.Prepend(reused_nodes_cord);
+    expected_chunks *= 2;
+    VerifyChunkIterator(reused_nodes_cord, expected_chunks);
+  }
+
+  RandomEngine rng(testing::GTEST_FLAG(random_seed));
+  absl::Cord flat_cord(RandomLowercaseString(&rng, 256));
+  absl::Cord subcords;
+  for (int i = 0; i < 128; ++i) subcords.Prepend(flat_cord.Subcord(i, 128));
+  VerifyChunkIterator(subcords, 128);
+}
+
+TEST(CordCharIterator, Traits) {
+  static_assert(std::is_copy_constructible<absl::Cord::CharIterator>::value,
+                "");
+  static_assert(std::is_copy_assignable<absl::Cord::CharIterator>::value, "");
+
+  // Move semantics to satisfy swappable via std::swap
+  static_assert(std::is_move_constructible<absl::Cord::CharIterator>::value,
+                "");
+  static_assert(std::is_move_assignable<absl::Cord::CharIterator>::value, "");
+
+  static_assert(
+      std::is_same<
+          std::iterator_traits<absl::Cord::CharIterator>::iterator_category,
+          std::input_iterator_tag>::value,
+      "");
+  static_assert(
+      std::is_same<std::iterator_traits<absl::Cord::CharIterator>::value_type,
+                   char>::value,
+      "");
+  static_assert(
+      std::is_same<
+          std::iterator_traits<absl::Cord::CharIterator>::difference_type,
+          ptrdiff_t>::value,
+      "");
+  static_assert(
+      std::is_same<std::iterator_traits<absl::Cord::CharIterator>::pointer,
+                   const char*>::value,
+      "");
+  static_assert(
+      std::is_same<std::iterator_traits<absl::Cord::CharIterator>::reference,
+                   const char&>::value,
+      "");
+}
+
+static void VerifyCharIterator(const absl::Cord& cord) {
+  EXPECT_EQ(cord.char_begin() == cord.char_end(), cord.empty());
+  EXPECT_EQ(cord.char_begin() != cord.char_end(), !cord.empty());
+
+  absl::Cord::CharRange range = cord.Chars();
+  EXPECT_EQ(range.begin() == range.end(), cord.empty());
+  EXPECT_EQ(range.begin() != range.end(), !cord.empty());
+
+  size_t i = 0;
+  absl::Cord::CharIterator pre_iter = cord.char_begin();
+  absl::Cord::CharIterator post_iter = cord.char_begin();
+  std::string content(cord);
+  while (pre_iter != cord.char_end() && post_iter != cord.char_end()) {
+    EXPECT_FALSE(pre_iter == cord.char_end());   // NOLINT: explicitly test ==
+    EXPECT_FALSE(post_iter == cord.char_end());  // NOLINT
+
+    EXPECT_LT(i, cord.size());
+    EXPECT_EQ(content[i], *pre_iter);
+
+    EXPECT_EQ(pre_iter, post_iter);
+    EXPECT_EQ(*pre_iter, *post_iter);
+    EXPECT_EQ(&*pre_iter, &*post_iter);
+
+    EXPECT_EQ(&*pre_iter, pre_iter.operator->());
+
+    const char* character_address = &*pre_iter;
+    absl::Cord::CharIterator copy = pre_iter;
+    ++copy;
+    EXPECT_EQ(character_address, &*pre_iter);
+
+    int n_equal_iterators = 0;
+    for (absl::Cord::CharIterator it = range.begin(); it != range.end(); ++it) {
+      n_equal_iterators += static_cast<int>(it == pre_iter);
+    }
+    EXPECT_EQ(n_equal_iterators, 1);
+
+    absl::Cord::CharIterator advance_iter = range.begin();
+    absl::Cord::Advance(&advance_iter, i);
+    EXPECT_EQ(pre_iter, advance_iter);
+
+    advance_iter = range.begin();
+    EXPECT_EQ(absl::Cord::AdvanceAndRead(&advance_iter, i), cord.Subcord(0, i));
+    EXPECT_EQ(pre_iter, advance_iter);
+
+    advance_iter = pre_iter;
+    absl::Cord::Advance(&advance_iter, cord.size() - i);
+    EXPECT_EQ(range.end(), advance_iter);
+
+    advance_iter = pre_iter;
+    EXPECT_EQ(absl::Cord::AdvanceAndRead(&advance_iter, cord.size() - i),
+              cord.Subcord(i, cord.size() - i));
+    EXPECT_EQ(range.end(), advance_iter);
+
+    ++i;
+    ++pre_iter;
+    post_iter++;
+  }
+  EXPECT_EQ(i, cord.size());
+  EXPECT_TRUE(pre_iter == cord.char_end());   // NOLINT: explicitly test ==
+  EXPECT_TRUE(post_iter == cord.char_end());  // NOLINT
+
+  absl::Cord::CharIterator zero_advanced_end = cord.char_end();
+  absl::Cord::Advance(&zero_advanced_end, 0);
+  EXPECT_EQ(zero_advanced_end, cord.char_end());
+
+  absl::Cord::CharIterator it = cord.char_begin();
+  for (absl::string_view chunk : cord.Chunks()) {
+    while (!chunk.empty()) {
+      EXPECT_EQ(absl::Cord::ChunkRemaining(it), chunk);
+      chunk.remove_prefix(1);
+      ++it;
+    }
+  }
+}
+
+TEST(CordCharIterator, Operations) {
+  absl::Cord empty_cord;
+  VerifyCharIterator(empty_cord);
+
+  absl::Cord small_buffer_cord("small cord");
+  VerifyCharIterator(small_buffer_cord);
+
+  absl::Cord flat_node_cord("larger than small buffer optimization");
+  VerifyCharIterator(flat_node_cord);
+
+  VerifyCharIterator(
+      absl::MakeFragmentedCord({"a ", "small ", "fragmented ", "cord ", "for ",
+                                "testing ", "character ", "iteration."}));
+
+  absl::Cord reused_nodes_cord("ghi");
+  reused_nodes_cord.Prepend(absl::Cord("def"));
+  reused_nodes_cord.Prepend(absl::Cord("abc"));
+  for (int i = 0; i < 4; ++i) {
+    reused_nodes_cord.Prepend(reused_nodes_cord);
+    VerifyCharIterator(reused_nodes_cord);
+  }
+
+  RandomEngine rng(testing::GTEST_FLAG(random_seed));
+  absl::Cord flat_cord(RandomLowercaseString(&rng, 256));
+  absl::Cord subcords;
+  for (int i = 0; i < 4; ++i) subcords.Prepend(flat_cord.Subcord(16 * i, 128));
+  VerifyCharIterator(subcords);
+}
+
+TEST(Cord, StreamingOutput) {
+  absl::Cord c =
+      absl::MakeFragmentedCord({"A ", "small ", "fragmented ", "Cord", "."});
+  std::stringstream output;
+  output << c;
+  EXPECT_EQ("A small fragmented Cord.", output.str());
+}
+
+TEST(Cord, ForEachChunk) {
+  for (int num_elements : {1, 10, 200}) {
+    SCOPED_TRACE(num_elements);
+    std::vector<std::string> cord_chunks;
+    for (int i = 0; i < num_elements; ++i) {
+      cord_chunks.push_back(absl::StrCat("[", i, "]"));
+    }
+    absl::Cord c = absl::MakeFragmentedCord(cord_chunks);
+
+    std::vector<std::string> iterated_chunks;
+    absl::CordTestPeer::ForEachChunk(c,
+                                     [&iterated_chunks](absl::string_view sv) {
+                                       iterated_chunks.emplace_back(sv);
+                                     });
+    EXPECT_EQ(iterated_chunks, cord_chunks);
+  }
+}
+
+TEST(Cord, SmallBufferAssignFromOwnData) {
+  constexpr size_t kMaxInline = 15;
+  std::string contents = "small buff cord";
+  EXPECT_EQ(contents.size(), kMaxInline);
+  for (size_t pos = 0; pos < contents.size(); ++pos) {
+    for (size_t count = contents.size() - pos; count > 0; --count) {
+      absl::Cord c(contents);
+      absl::string_view flat = c.Flatten();
+      c = flat.substr(pos, count);
+      EXPECT_EQ(c, contents.substr(pos, count))
+          << "pos = " << pos << "; count = " << count;
+    }
+  }
+}