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absl/strings/str_split_test.cc

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+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/strings/str_split.h"
+
+#include <climits>
+#include <cstdlib>
+#include <cstring>
+#include <deque>
+#include <limits>
+#include <list>
+#include <map>
+#include <memory>
+#include <string>
+#include <unordered_map>
+#include <unordered_set>
+#include <vector>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "absl/base/dynamic_annotations.h"  // for RunningOnValgrind
+#include "absl/base/macros.h"
+#include "absl/base/port.h"
+#include "absl/strings/numbers.h"
+
+namespace {
+
+using ::testing::ElementsAre;
+using ::testing::Pair;
+using ::testing::UnorderedElementsAre;
+
+// This tests the overall split API, which is made up of the absl::StrSplit()
+// function and the Delimiter objects in the absl:: namespace.
+// This TEST macro is outside of any namespace to require full specification of
+// namespaces just like callers will need to use.
+TEST(Split, APIExamples) {
+  {
+    // Passes std::string delimiter. Assumes the default of Literal.
+    std::vector<std::string> v = absl::StrSplit("a,b,c", ',');
+    EXPECT_THAT(v, ElementsAre("a", "b", "c"));
+
+    // Equivalent to...
+    using absl::ByString;
+    v = absl::StrSplit("a,b,c", ByString(","));
+    EXPECT_THAT(v, ElementsAre("a", "b", "c"));
+
+    // Equivalent to...
+    EXPECT_THAT(absl::StrSplit("a,b,c", ByString(",")),
+                ElementsAre("a", "b", "c"));
+  }
+
+  {
+    // Same as above, but using a single character as the delimiter.
+    std::vector<std::string> v = absl::StrSplit("a,b,c", ',');
+    EXPECT_THAT(v, ElementsAre("a", "b", "c"));
+
+    // Equivalent to...
+    using absl::ByChar;
+    v = absl::StrSplit("a,b,c", ByChar(','));
+    EXPECT_THAT(v, ElementsAre("a", "b", "c"));
+  }
+
+  {
+    // Same as above, but using std::string
+    std::vector<std::string> v = absl::StrSplit("a,b,c", ',');
+    EXPECT_THAT(v, ElementsAre("a", "b", "c"));
+
+    // Equivalent to...
+    using absl::ByChar;
+    v = absl::StrSplit("a,b,c", ByChar(','));
+    EXPECT_THAT(v, ElementsAre("a", "b", "c"));
+  }
+
+  {
+    // Uses the Literal std::string "=>" as the delimiter.
+    const std::vector<std::string> v = absl::StrSplit("a=>b=>c", "=>");
+    EXPECT_THAT(v, ElementsAre("a", "b", "c"));
+  }
+
+  {
+    // The substrings are returned as string_views, eliminating copying.
+    std::vector<absl::string_view> v = absl::StrSplit("a,b,c", ',');
+    EXPECT_THAT(v, ElementsAre("a", "b", "c"));
+  }
+
+  {
+    // Leading and trailing empty substrings.
+    std::vector<std::string> v = absl::StrSplit(",a,b,c,", ',');
+    EXPECT_THAT(v, ElementsAre("", "a", "b", "c", ""));
+  }
+
+  {
+    // Splits on a delimiter that is not found.
+    std::vector<std::string> v = absl::StrSplit("abc", ',');
+    EXPECT_THAT(v, ElementsAre("abc"));
+  }
+
+  {
+    // Splits the input std::string into individual characters by using an empty
+    // std::string as the delimiter.
+    std::vector<std::string> v = absl::StrSplit("abc", "");
+    EXPECT_THAT(v, ElementsAre("a", "b", "c"));
+  }
+
+  {
+    // Splits std::string data with embedded NUL characters, using NUL as the
+    // delimiter. A simple delimiter of "\0" doesn't work because strlen() will
+    // say that's the empty std::string when constructing the absl::string_view
+    // delimiter. Instead, a non-empty std::string containing NUL can be used as the
+    // delimiter.
+    std::string embedded_nulls("a\0b\0c", 5);
+    std::string null_delim("\0", 1);
+    std::vector<std::string> v = absl::StrSplit(embedded_nulls, null_delim);
+    EXPECT_THAT(v, ElementsAre("a", "b", "c"));
+  }
+
+  {
+    // Stores first two split strings as the members in a std::pair.
+    std::pair<std::string, std::string> p = absl::StrSplit("a,b,c", ',');
+    EXPECT_EQ("a", p.first);
+    EXPECT_EQ("b", p.second);
+    // "c" is omitted because std::pair can hold only two elements.
+  }
+
+  {
+    // Results stored in std::set<std::string>
+    std::set<std::string> v = absl::StrSplit("a,b,c,a,b,c,a,b,c", ',');
+    EXPECT_THAT(v, ElementsAre("a", "b", "c"));
+  }
+
+  {
+    // Uses a non-const char* delimiter.
+    char a[] = ",";
+    char* d = a + 0;
+    std::vector<std::string> v = absl::StrSplit("a,b,c", d);
+    EXPECT_THAT(v, ElementsAre("a", "b", "c"));
+  }
+
+  {
+    // Results split using either of , or ;
+    using absl::ByAnyChar;
+    std::vector<std::string> v = absl::StrSplit("a,b;c", ByAnyChar(",;"));
+    EXPECT_THAT(v, ElementsAre("a", "b", "c"));
+  }
+
+  {
+    // Uses the SkipWhitespace predicate.
+    using absl::SkipWhitespace;
+    std::vector<std::string> v = absl::StrSplit("a, ,,b,", ',', SkipWhitespace());
+    EXPECT_THAT(v, ElementsAre("a", "b"));
+  }
+
+  {
+    // Uses the ByLength delimiter.
+    using absl::ByLength;
+    std::vector<std::string> v = absl::StrSplit("abcdefg", ByLength(3));
+    EXPECT_THAT(v, ElementsAre("abc", "def", "g"));
+  }
+
+  {
+    // Results stored in a std::map.
+    std::map<std::string, std::string> m = absl::StrSplit("a,1,b,2,a,3", ',');
+    EXPECT_EQ(2, m.size());
+    EXPECT_EQ("3", m["a"]);
+    EXPECT_EQ("2", m["b"]);
+  }
+
+  {
+    // Results stored in a std::multimap.
+    std::multimap<std::string, std::string> m = absl::StrSplit("a,1,b,2,a,3", ',');
+    EXPECT_EQ(3, m.size());
+    auto it = m.find("a");
+    EXPECT_EQ("1", it->second);
+    ++it;
+    EXPECT_EQ("3", it->second);
+    it = m.find("b");
+    EXPECT_EQ("2", it->second);
+  }
+
+  {
+    // Demonstrates use in a range-based for loop in C++11.
+    std::string s = "x,x,x,x,x,x,x";
+    for (absl::string_view sp : absl::StrSplit(s, ',')) {
+      EXPECT_EQ("x", sp);
+    }
+  }
+
+  {
+    // Demonstrates use with a Predicate in a range-based for loop.
+    using absl::SkipWhitespace;
+    std::string s = " ,x,,x,,x,x,x,,";
+    for (absl::string_view sp : absl::StrSplit(s, ',', SkipWhitespace())) {
+      EXPECT_EQ("x", sp);
+    }
+  }
+
+  {
+    // Demonstrates a "smart" split to std::map using two separate calls to
+    // absl::StrSplit. One call to split the records, and another call to split
+    // the keys and values. This also uses the Limit delimiter so that the
+    // std::string "a=b=c" will split to "a" -> "b=c".
+    std::map<std::string, std::string> m;
+    for (absl::string_view sp : absl::StrSplit("a=b=c,d=e,f=,g", ',')) {
+      m.insert(absl::StrSplit(sp, absl::MaxSplits('=', 1)));
+    }
+    EXPECT_EQ("b=c", m.find("a")->second);
+    EXPECT_EQ("e", m.find("d")->second);
+    EXPECT_EQ("", m.find("f")->second);
+    EXPECT_EQ("", m.find("g")->second);
+  }
+}
+
+//
+// Tests for SplitIterator
+//
+
+TEST(SplitIterator, Basics) {
+  auto splitter = absl::StrSplit("a,b", ',');
+  auto it = splitter.begin();
+  auto end = splitter.end();
+
+  EXPECT_NE(it, end);
+  EXPECT_EQ("a", *it);  // tests dereference
+  ++it;  // tests preincrement
+  EXPECT_NE(it, end);
+  EXPECT_EQ("b", std::string(it->data(), it->size()));  // tests dereference as ptr
+  it++;  // tests postincrement
+  EXPECT_EQ(it, end);
+}
+
+// Simple Predicate to skip a particular std::string.
+class Skip {
+ public:
+  explicit Skip(const std::string& s) : s_(s) {}
+  bool operator()(absl::string_view sp) { return sp != s_; }
+
+ private:
+  std::string s_;
+};
+
+TEST(SplitIterator, Predicate) {
+  auto splitter = absl::StrSplit("a,b,c", ',', Skip("b"));
+  auto it = splitter.begin();
+  auto end = splitter.end();
+
+  EXPECT_NE(it, end);
+  EXPECT_EQ("a", *it);  // tests dereference
+  ++it;  // tests preincrement -- "b" should be skipped here.
+  EXPECT_NE(it, end);
+  EXPECT_EQ("c", std::string(it->data(), it->size()));  // tests dereference as ptr
+  it++;  // tests postincrement
+  EXPECT_EQ(it, end);
+}
+
+TEST(SplitIterator, EdgeCases) {
+  // Expected input and output, assuming a delimiter of ','
+  struct {
+    std::string in;
+    std::vector<std::string> expect;
+  } specs[] = {
+    {"", {""}},
+    {"foo", {"foo"}},
+    {",", {"", ""}},
+    {",foo", {"", "foo"}},
+    {"foo,", {"foo", ""}},
+    {",foo,", {"", "foo", ""}},
+    {"foo,bar", {"foo", "bar"}},
+  };
+
+  for (const auto& spec : specs) {
+    SCOPED_TRACE(spec.in);
+    auto splitter = absl::StrSplit(spec.in, ',');
+    auto it = splitter.begin();
+    auto end = splitter.end();
+    for (const auto& expected : spec.expect) {
+      EXPECT_NE(it, end);
+      EXPECT_EQ(expected, *it++);
+    }
+    EXPECT_EQ(it, end);
+  }
+}
+
+TEST(Splitter, Const) {
+  const auto splitter = absl::StrSplit("a,b,c", ',');
+  EXPECT_THAT(splitter, ElementsAre("a", "b", "c"));
+}
+
+TEST(Split, EmptyAndNull) {
+  // Attention: Splitting a null absl::string_view is different than splitting
+  // an empty absl::string_view even though both string_views are considered
+  // equal. This behavior is likely surprising and undesirable. However, to
+  // maintain backward compatibility, there is a small "hack" in
+  // str_split_internal.h that preserves this behavior. If that behavior is ever
+  // changed/fixed, this test will need to be updated.
+  EXPECT_THAT(absl::StrSplit(absl::string_view(""), '-'), ElementsAre(""));
+  EXPECT_THAT(absl::StrSplit(absl::string_view(), '-'), ElementsAre());
+}
+
+TEST(SplitIterator, EqualityAsEndCondition) {
+  auto splitter = absl::StrSplit("a,b,c", ',');
+  auto it = splitter.begin();
+  auto it2 = it;
+
+  // Increments it2 twice to point to "c" in the input text.
+  ++it2;
+  ++it2;
+  EXPECT_EQ("c", *it2);
+
+  // This test uses a non-end SplitIterator as the terminating condition in a
+  // for loop. This relies on SplitIterator equality for non-end SplitIterators
+  // working correctly. At this point it2 points to "c", and we use that as the
+  // "end" condition in this test.
+  std::vector<absl::string_view> v;
+  for (; it != it2; ++it) {
+    v.push_back(*it);
+  }
+  EXPECT_THAT(v, ElementsAre("a", "b"));
+}
+
+//
+// Tests for Splitter
+//
+
+TEST(Splitter, RangeIterators) {
+  auto splitter = absl::StrSplit("a,b,c", ',');
+  std::vector<absl::string_view> output;
+  for (const absl::string_view p : splitter) {
+    output.push_back(p);
+  }
+  EXPECT_THAT(output, ElementsAre("a", "b", "c"));
+}
+
+// Some template functions for use in testing conversion operators
+template <typename ContainerType, typename Splitter>
+void TestConversionOperator(const Splitter& splitter) {
+  ContainerType output = splitter;
+  EXPECT_THAT(output, UnorderedElementsAre("a", "b", "c", "d"));
+}
+
+template <typename MapType, typename Splitter>
+void TestMapConversionOperator(const Splitter& splitter) {
+  MapType m = splitter;
+  EXPECT_THAT(m, UnorderedElementsAre(Pair("a", "b"), Pair("c", "d")));
+}
+
+template <typename FirstType, typename SecondType, typename Splitter>
+void TestPairConversionOperator(const Splitter& splitter) {
+  std::pair<FirstType, SecondType> p = splitter;
+  EXPECT_EQ(p, (std::pair<FirstType, SecondType>("a", "b")));
+}
+
+TEST(Splitter, ConversionOperator) {
+  auto splitter = absl::StrSplit("a,b,c,d", ',');
+
+  TestConversionOperator<std::vector<absl::string_view>>(splitter);
+  TestConversionOperator<std::vector<std::string>>(splitter);
+  TestConversionOperator<std::list<absl::string_view>>(splitter);
+  TestConversionOperator<std::list<std::string>>(splitter);
+  TestConversionOperator<std::deque<absl::string_view>>(splitter);
+  TestConversionOperator<std::deque<std::string>>(splitter);
+  TestConversionOperator<std::set<absl::string_view>>(splitter);
+  TestConversionOperator<std::set<std::string>>(splitter);
+  TestConversionOperator<std::multiset<absl::string_view>>(splitter);
+  TestConversionOperator<std::multiset<std::string>>(splitter);
+  TestConversionOperator<std::unordered_set<std::string>>(splitter);
+
+  // Tests conversion to map-like objects.
+
+  TestMapConversionOperator<std::map<absl::string_view, absl::string_view>>(
+      splitter);
+  TestMapConversionOperator<std::map<absl::string_view, std::string>>(splitter);
+  TestMapConversionOperator<std::map<std::string, absl::string_view>>(splitter);
+  TestMapConversionOperator<std::map<std::string, std::string>>(splitter);
+  TestMapConversionOperator<
+      std::multimap<absl::string_view, absl::string_view>>(splitter);
+  TestMapConversionOperator<std::multimap<absl::string_view, std::string>>(splitter);
+  TestMapConversionOperator<std::multimap<std::string, absl::string_view>>(splitter);
+  TestMapConversionOperator<std::multimap<std::string, std::string>>(splitter);
+  TestMapConversionOperator<std::unordered_map<std::string, std::string>>(splitter);
+
+  // Tests conversion to std::pair
+
+  TestPairConversionOperator<absl::string_view, absl::string_view>(splitter);
+  TestPairConversionOperator<absl::string_view, std::string>(splitter);
+  TestPairConversionOperator<std::string, absl::string_view>(splitter);
+  TestPairConversionOperator<std::string, std::string>(splitter);
+}
+
+// A few additional tests for conversion to std::pair. This conversion is
+// different from others because a std::pair always has exactly two elements:
+// .first and .second. The split has to work even when the split has
+// less-than, equal-to, and more-than 2 strings.
+TEST(Splitter, ToPair) {
+  {
+    // Empty std::string
+    std::pair<std::string, std::string> p = absl::StrSplit("", ',');
+    EXPECT_EQ("", p.first);
+    EXPECT_EQ("", p.second);
+  }
+
+  {
+    // Only first
+    std::pair<std::string, std::string> p = absl::StrSplit("a", ',');
+    EXPECT_EQ("a", p.first);
+    EXPECT_EQ("", p.second);
+  }
+
+  {
+    // Only second
+    std::pair<std::string, std::string> p = absl::StrSplit(",b", ',');
+    EXPECT_EQ("", p.first);
+    EXPECT_EQ("b", p.second);
+  }
+
+  {
+    // First and second.
+    std::pair<std::string, std::string> p = absl::StrSplit("a,b", ',');
+    EXPECT_EQ("a", p.first);
+    EXPECT_EQ("b", p.second);
+  }
+
+  {
+    // First and second and then more stuff that will be ignored.
+    std::pair<std::string, std::string> p = absl::StrSplit("a,b,c", ',');
+    EXPECT_EQ("a", p.first);
+    EXPECT_EQ("b", p.second);
+    // "c" is omitted.
+  }
+}
+
+TEST(Splitter, Predicates) {
+  static const char kTestChars[] = ",a, ,b,";
+  using absl::AllowEmpty;
+  using absl::SkipEmpty;
+  using absl::SkipWhitespace;
+
+  {
+    // No predicate. Does not skip empties.
+    auto splitter = absl::StrSplit(kTestChars, ',');
+    std::vector<std::string> v = splitter;
+    EXPECT_THAT(v, ElementsAre("", "a", " ", "b", ""));
+  }
+
+  {
+    // Allows empty strings. Same behavior as no predicate at all.
+    auto splitter = absl::StrSplit(kTestChars, ',', AllowEmpty());
+    std::vector<std::string> v_allowempty = splitter;
+    EXPECT_THAT(v_allowempty, ElementsAre("", "a", " ", "b", ""));
+
+    // Ensures AllowEmpty equals the behavior with no predicate.
+    auto splitter_nopredicate = absl::StrSplit(kTestChars, ',');
+    std::vector<std::string> v_nopredicate = splitter_nopredicate;
+    EXPECT_EQ(v_allowempty, v_nopredicate);
+  }
+
+  {
+    // Skips empty strings.
+    auto splitter = absl::StrSplit(kTestChars, ',', SkipEmpty());
+    std::vector<std::string> v = splitter;
+    EXPECT_THAT(v, ElementsAre("a", " ", "b"));
+  }
+
+  {
+    // Skips empty and all-whitespace strings.
+    auto splitter = absl::StrSplit(kTestChars, ',', SkipWhitespace());
+    std::vector<std::string> v = splitter;
+    EXPECT_THAT(v, ElementsAre("a", "b"));
+  }
+}
+
+//
+// Tests for StrSplit()
+//
+
+TEST(Split, Basics) {
+  {
+    // Doesn't really do anything useful because the return value is ignored,
+    // but it should work.
+    absl::StrSplit("a,b,c", ',');
+  }
+
+  {
+    std::vector<absl::string_view> v = absl::StrSplit("a,b,c", ',');
+    EXPECT_THAT(v, ElementsAre("a", "b", "c"));
+  }
+
+  {
+    std::vector<std::string> v = absl::StrSplit("a,b,c", ',');
+    EXPECT_THAT(v, ElementsAre("a", "b", "c"));
+  }
+
+  {
+    // Ensures that assignment works. This requires a little extra work with
+    // C++11 because of overloads with initializer_list.
+    std::vector<std::string> v;
+    v = absl::StrSplit("a,b,c", ',');
+
+    EXPECT_THAT(v, ElementsAre("a", "b", "c"));
+    std::map<std::string, std::string> m;
+    m = absl::StrSplit("a,b,c", ',');
+    EXPECT_EQ(2, m.size());
+    std::unordered_map<std::string, std::string> hm;
+    hm = absl::StrSplit("a,b,c", ',');
+    EXPECT_EQ(2, hm.size());
+  }
+}
+
+absl::string_view ReturnStringView() { return "Hello World"; }
+const char* ReturnConstCharP() { return "Hello World"; }
+char* ReturnCharP() { return const_cast<char*>("Hello World"); }
+
+TEST(Split, AcceptsCertainTemporaries) {
+  std::vector<std::string> v;
+  v = absl::StrSplit(ReturnStringView(), ' ');
+  EXPECT_THAT(v, ElementsAre("Hello", "World"));
+  v = absl::StrSplit(ReturnConstCharP(), ' ');
+  EXPECT_THAT(v, ElementsAre("Hello", "World"));
+  v = absl::StrSplit(ReturnCharP(), ' ');
+  EXPECT_THAT(v, ElementsAre("Hello", "World"));
+}
+
+TEST(Split, Temporary) {
+  // Use a std::string longer than the small-std::string-optimization length, so that when
+  // the temporary is destroyed, if the splitter keeps a reference to the
+  // std::string's contents, it'll reference freed memory instead of just dead
+  // on-stack memory.
+  const char input[] = "a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u";
+  EXPECT_LT(sizeof(std::string), ABSL_ARRAYSIZE(input))
+      << "Input should be larger than fits on the stack.";
+
+  // This happens more often in C++11 as part of a range-based for loop.
+  auto splitter = absl::StrSplit(std::string(input), ',');
+  std::string expected = "a";
+  for (absl::string_view letter : splitter) {
+    EXPECT_EQ(expected, letter);
+    ++expected[0];
+  }
+  EXPECT_EQ("v", expected);
+
+  // This happens more often in C++11 as part of a range-based for loop.
+  auto std_splitter = absl::StrSplit(std::string(input), ',');
+  expected = "a";
+  for (absl::string_view letter : std_splitter) {
+    EXPECT_EQ(expected, letter);
+    ++expected[0];
+  }
+  EXPECT_EQ("v", expected);
+}
+
+template <typename T>
+static std::unique_ptr<T> CopyToHeap(const T& value) {
+  return std::unique_ptr<T>(new T(value));
+}
+
+TEST(Split, LvalueCaptureIsCopyable) {
+  std::string input = "a,b";
+  auto heap_splitter = CopyToHeap(absl::StrSplit(input, ','));
+  auto stack_splitter = *heap_splitter;
+  heap_splitter.reset();
+  std::vector<std::string> result = stack_splitter;
+  EXPECT_THAT(result, testing::ElementsAre("a", "b"));
+}
+
+TEST(Split, TemporaryCaptureIsCopyable) {
+  auto heap_splitter = CopyToHeap(absl::StrSplit(std::string("a,b"), ','));
+  auto stack_splitter = *heap_splitter;
+  heap_splitter.reset();
+  std::vector<std::string> result = stack_splitter;
+  EXPECT_THAT(result, testing::ElementsAre("a", "b"));
+}
+
+TEST(Split, SplitterIsCopyableAndMoveable) {
+  auto a = absl::StrSplit("foo", '-');
+
+  // Ensures that the following expressions compile.
+  auto b = a;             // Copy construct
+  auto c = std::move(a);  // Move construct
+  b = c;                  // Copy assign
+  c = std::move(b);       // Move assign
+
+  EXPECT_THAT(c, ElementsAre("foo"));
+}
+
+TEST(Split, StringDelimiter) {
+  {
+    std::vector<absl::string_view> v = absl::StrSplit("a,b", ',');
+    EXPECT_THAT(v, ElementsAre("a", "b"));
+  }
+
+  {
+    std::vector<absl::string_view> v = absl::StrSplit("a,b", std::string(","));
+    EXPECT_THAT(v, ElementsAre("a", "b"));
+  }
+
+  {
+    std::vector<absl::string_view> v =
+        absl::StrSplit("a,b", absl::string_view(","));
+    EXPECT_THAT(v, ElementsAre("a", "b"));
+  }
+}
+
+TEST(Split, UTF8) {
+  // Tests splitting utf8 strings and utf8 delimiters.
+  {
+    // A utf8 input std::string with an ascii delimiter.
+    std::vector<absl::string_view> v = absl::StrSplit("a,κόσμε", ',');
+    EXPECT_THAT(v, ElementsAre("a", "κόσμε"));
+  }
+
+  {
+    // A utf8 input std::string and a utf8 delimiter.
+    std::vector<absl::string_view> v = absl::StrSplit("a,κόσμε,b", ",κόσμε,");
+    EXPECT_THAT(v, ElementsAre("a", "b"));
+  }
+
+  {
+    // A utf8 input std::string and ByAnyChar with ascii chars.
+    std::vector<absl::string_view> v =
+        absl::StrSplit("Foo hällo th丞re", absl::ByAnyChar(" \t"));
+    EXPECT_THAT(v, ElementsAre("Foo", "hällo", "th丞re"));
+  }
+}
+
+TEST(Split, EmptyStringDelimiter) {
+  {
+    std::vector<std::string> v = absl::StrSplit("", "");
+    EXPECT_THAT(v, ElementsAre(""));
+  }
+
+  {
+    std::vector<std::string> v = absl::StrSplit("a", "");
+    EXPECT_THAT(v, ElementsAre("a"));
+  }
+
+  {
+    std::vector<std::string> v = absl::StrSplit("ab", "");
+    EXPECT_THAT(v, ElementsAre("a", "b"));
+  }
+
+  {
+    std::vector<std::string> v = absl::StrSplit("a b", "");
+    EXPECT_THAT(v, ElementsAre("a", " ", "b"));
+  }
+}
+
+TEST(Split, SubstrDelimiter) {
+  std::vector<absl::string_view> results;
+  absl::string_view delim("//");
+
+  results = absl::StrSplit("", delim);
+  EXPECT_THAT(results, ElementsAre(""));
+
+  results = absl::StrSplit("//", delim);
+  EXPECT_THAT(results, ElementsAre("", ""));
+
+  results = absl::StrSplit("ab", delim);
+  EXPECT_THAT(results, ElementsAre("ab"));
+
+  results = absl::StrSplit("ab//", delim);
+  EXPECT_THAT(results, ElementsAre("ab", ""));
+
+  results = absl::StrSplit("ab/", delim);
+  EXPECT_THAT(results, ElementsAre("ab/"));
+
+  results = absl::StrSplit("a/b", delim);
+  EXPECT_THAT(results, ElementsAre("a/b"));
+
+  results = absl::StrSplit("a//b", delim);
+  EXPECT_THAT(results, ElementsAre("a", "b"));
+
+  results = absl::StrSplit("a///b", delim);
+  EXPECT_THAT(results, ElementsAre("a", "/b"));
+
+  results = absl::StrSplit("a////b", delim);
+  EXPECT_THAT(results, ElementsAre("a", "", "b"));
+}
+
+TEST(Split, EmptyResults) {
+  std::vector<absl::string_view> results;
+
+  results = absl::StrSplit("", '#');
+  EXPECT_THAT(results, ElementsAre(""));
+
+  results = absl::StrSplit("#", '#');
+  EXPECT_THAT(results, ElementsAre("", ""));
+
+  results = absl::StrSplit("#cd", '#');
+  EXPECT_THAT(results, ElementsAre("", "cd"));
+
+  results = absl::StrSplit("ab#cd#", '#');
+  EXPECT_THAT(results, ElementsAre("ab", "cd", ""));
+
+  results = absl::StrSplit("ab##cd", '#');
+  EXPECT_THAT(results, ElementsAre("ab", "", "cd"));
+
+  results = absl::StrSplit("ab##", '#');
+  EXPECT_THAT(results, ElementsAre("ab", "", ""));
+
+  results = absl::StrSplit("ab#ab#", '#');
+  EXPECT_THAT(results, ElementsAre("ab", "ab", ""));
+
+  results = absl::StrSplit("aaaa", 'a');
+  EXPECT_THAT(results, ElementsAre("", "", "", "", ""));
+
+  results = absl::StrSplit("", '#', absl::SkipEmpty());
+  EXPECT_THAT(results, ElementsAre());
+}
+
+template <typename Delimiter>
+static bool IsFoundAtStartingPos(absl::string_view text, Delimiter d,
+                                 size_t starting_pos, int expected_pos) {
+  absl::string_view found = d.Find(text, starting_pos);
+  return found.data() != text.end() &&
+         expected_pos == found.data() - text.data();
+}
+
+// Helper function for testing Delimiter objects. Returns true if the given
+// Delimiter is found in the given std::string at the given position. This function
+// tests two cases:
+//   1. The actual text given, staring at position 0
+//   2. The text given with leading padding that should be ignored
+template <typename Delimiter>
+static bool IsFoundAt(absl::string_view text, Delimiter d, int expected_pos) {
+  const std::string leading_text = ",x,y,z,";
+  return IsFoundAtStartingPos(text, d, 0, expected_pos) &&
+         IsFoundAtStartingPos(leading_text + std::string(text), d,
+                              leading_text.length(),
+                              expected_pos + leading_text.length());
+}
+
+//
+// Tests for Literal
+//
+
+// Tests using any delimiter that represents a single comma.
+template <typename Delimiter>
+void TestComma(Delimiter d) {
+  EXPECT_TRUE(IsFoundAt(",", d, 0));
+  EXPECT_TRUE(IsFoundAt("a,", d, 1));
+  EXPECT_TRUE(IsFoundAt(",b", d, 0));
+  EXPECT_TRUE(IsFoundAt("a,b", d, 1));
+  EXPECT_TRUE(IsFoundAt("a,b,", d, 1));
+  EXPECT_TRUE(IsFoundAt("a,b,c", d, 1));
+  EXPECT_FALSE(IsFoundAt("", d, -1));
+  EXPECT_FALSE(IsFoundAt(" ", d, -1));
+  EXPECT_FALSE(IsFoundAt("a", d, -1));
+  EXPECT_FALSE(IsFoundAt("a b c", d, -1));
+  EXPECT_FALSE(IsFoundAt("a;b;c", d, -1));
+  EXPECT_FALSE(IsFoundAt(";", d, -1));
+}
+
+TEST(Delimiter, Literal) {
+  using absl::ByString;
+  TestComma(ByString(","));
+
+  // Works as named variable.
+  ByString comma_string(",");
+  TestComma(comma_string);
+
+  // The first occurrence of empty std::string ("") in a std::string is at position 0.
+  // There is a test below that demonstrates this for absl::string_view::find().
+  // If the ByString delimiter returned position 0 for this, there would
+  // be an infinite loop in the SplitIterator code. To avoid this, empty std::string
+  // is a special case in that it always returns the item at position 1.
+  absl::string_view abc("abc");
+  EXPECT_EQ(0, abc.find(""));  // "" is found at position 0
+  ByString empty("");
+  EXPECT_FALSE(IsFoundAt("", empty, 0));
+  EXPECT_FALSE(IsFoundAt("a", empty, 0));
+  EXPECT_TRUE(IsFoundAt("ab", empty, 1));
+  EXPECT_TRUE(IsFoundAt("abc", empty, 1));
+}
+
+TEST(Split, ByChar) {
+  using absl::ByChar;
+  TestComma(ByChar(','));
+
+  // Works as named variable.
+  ByChar comma_char(',');
+  TestComma(comma_char);
+}
+
+//
+// Tests for ByAnyChar
+//
+
+TEST(Delimiter, ByAnyChar) {
+  using absl::ByAnyChar;
+  ByAnyChar one_delim(",");
+  // Found
+  EXPECT_TRUE(IsFoundAt(",", one_delim, 0));
+  EXPECT_TRUE(IsFoundAt("a,", one_delim, 1));
+  EXPECT_TRUE(IsFoundAt("a,b", one_delim, 1));
+  EXPECT_TRUE(IsFoundAt(",b", one_delim, 0));
+  // Not found
+  EXPECT_FALSE(IsFoundAt("", one_delim, -1));
+  EXPECT_FALSE(IsFoundAt(" ", one_delim, -1));
+  EXPECT_FALSE(IsFoundAt("a", one_delim, -1));
+  EXPECT_FALSE(IsFoundAt("a;b;c", one_delim, -1));
+  EXPECT_FALSE(IsFoundAt(";", one_delim, -1));
+
+  ByAnyChar two_delims(",;");
+  // Found
+  EXPECT_TRUE(IsFoundAt(",", two_delims, 0));
+  EXPECT_TRUE(IsFoundAt(";", two_delims, 0));
+  EXPECT_TRUE(IsFoundAt(",;", two_delims, 0));
+  EXPECT_TRUE(IsFoundAt(";,", two_delims, 0));
+  EXPECT_TRUE(IsFoundAt(",;b", two_delims, 0));
+  EXPECT_TRUE(IsFoundAt(";,b", two_delims, 0));
+  EXPECT_TRUE(IsFoundAt("a;,", two_delims, 1));
+  EXPECT_TRUE(IsFoundAt("a,;", two_delims, 1));
+  EXPECT_TRUE(IsFoundAt("a;,b", two_delims, 1));
+  EXPECT_TRUE(IsFoundAt("a,;b", two_delims, 1));
+  // Not found
+  EXPECT_FALSE(IsFoundAt("", two_delims, -1));
+  EXPECT_FALSE(IsFoundAt(" ", two_delims, -1));
+  EXPECT_FALSE(IsFoundAt("a", two_delims, -1));
+  EXPECT_FALSE(IsFoundAt("a=b=c", two_delims, -1));
+  EXPECT_FALSE(IsFoundAt("=", two_delims, -1));
+
+  // ByAnyChar behaves just like ByString when given a delimiter of empty
+  // std::string. That is, it always returns a zero-length absl::string_view
+  // referring to the item at position 1, not position 0.
+  ByAnyChar empty("");
+  EXPECT_FALSE(IsFoundAt("", empty, 0));
+  EXPECT_FALSE(IsFoundAt("a", empty, 0));
+  EXPECT_TRUE(IsFoundAt("ab", empty, 1));
+  EXPECT_TRUE(IsFoundAt("abc", empty, 1));
+}
+
+//
+// Tests for ByLength
+//
+
+TEST(Delimiter, ByLength) {
+  using absl::ByLength;
+
+  ByLength four_char_delim(4);
+
+  // Found
+  EXPECT_TRUE(IsFoundAt("abcde", four_char_delim, 4));
+  EXPECT_TRUE(IsFoundAt("abcdefghijklmnopqrstuvwxyz", four_char_delim, 4));
+  EXPECT_TRUE(IsFoundAt("a b,c\nd", four_char_delim, 4));
+  // Not found
+  EXPECT_FALSE(IsFoundAt("", four_char_delim, 0));
+  EXPECT_FALSE(IsFoundAt("a", four_char_delim, 0));
+  EXPECT_FALSE(IsFoundAt("ab", four_char_delim, 0));
+  EXPECT_FALSE(IsFoundAt("abc", four_char_delim, 0));
+  EXPECT_FALSE(IsFoundAt("abcd", four_char_delim, 0));
+}
+
+// Allocates too much memory for TSan and MSan.
+#if !defined(THREAD_SANITIZER) && !defined(MEMORY_SANITIZER)
+TEST(Split, WorksWithLargeStrings) {
+  if (sizeof(size_t) > 4 && !RunningOnValgrind()) {
+    std::string s(1ULL << 31, 'x');
+    s.push_back('-');  // 2G + 1 byte
+    std::vector<absl::string_view> v = absl::StrSplit(s, '-');
+    EXPECT_EQ(2, v.size());
+    // The first element will contain 2G of 'x's.
+    // testing::StartsWith is too slow with a 2G std::string.
+    EXPECT_EQ('x', v[0][0]);
+    EXPECT_EQ('x', v[0][1]);
+    EXPECT_EQ('x', v[0][3]);
+    EXPECT_EQ("", v[1]);
+  }
+}
+#endif  // THREAD_SANITIZER
+
+TEST(SplitInternalTest, TypeTraits) {
+  EXPECT_FALSE(absl::strings_internal::HasMappedType<int>::value);
+  EXPECT_TRUE(
+      (absl::strings_internal::HasMappedType<std::map<int, int>>::value));
+  EXPECT_FALSE(absl::strings_internal::HasValueType<int>::value);
+  EXPECT_TRUE(
+      (absl::strings_internal::HasValueType<std::map<int, int>>::value));
+  EXPECT_FALSE(absl::strings_internal::HasConstIterator<int>::value);
+  EXPECT_TRUE(
+      (absl::strings_internal::HasConstIterator<std::map<int, int>>::value));
+  EXPECT_FALSE(absl::strings_internal::IsInitializerList<int>::value);
+  EXPECT_TRUE((absl::strings_internal::IsInitializerList<
+               std::initializer_list<int>>::value));
+}
+
+}  // namespace