esphome/tests/components/core/test_string_ref.cpp

#include <gtest/gtest.h>

#include "esphome/core/string_ref.h"

#include <iterator>
#include <string>

namespace esphome::core::testing {

TEST(StringRefStartsWith, ProperPrefixMatches) {
  StringRef ref("FR:R20:12345", 12);
  EXPECT_TRUE(ref.starts_with("FR:"));
}

TEST(StringRefStartsWith, WholeStringIsAPrefixOfItself) {
  StringRef ref("TP96", 4);
  EXPECT_TRUE(ref.starts_with("TP96"));
}

TEST(StringRefStartsWith, PrefixLongerThanViewFails) {
  StringRef ref("TP", 2);
  EXPECT_FALSE(ref.starts_with("TP96"));
}

TEST(StringRefStartsWith, DifferentContentFails) {
  StringRef ref("TP96", 4);
  EXPECT_FALSE(ref.starts_with("FR:"));
}

TEST(StringRefStartsWith, EmptyPrefixAlwaysMatches) {
  StringRef ref("abc", 3);
  EXPECT_TRUE(ref.starts_with(""));
  StringRef empty;
  EXPECT_TRUE(empty.starts_with(""));
}

TEST(StringRefStartsWith, EmptyViewOnlyMatchesEmptyPrefix) {
  StringRef empty;
  EXPECT_FALSE(empty.starts_with("a"));
}

TEST(StringRefStartsWith, WorksOnANonTerminatedBuffer) {
  // The reason the helper exists: a bounded view over a buffer with no
  // terminator anywhere near the viewed bytes.
  const char raw[] = {'R', 'a', 'd', 'o', 'n', 'X'};
  StringRef ref(raw, 5);
  EXPECT_TRUE(ref.starts_with("Radon"));
  EXPECT_FALSE(ref.starts_with("RadonEye"));
  EXPECT_FALSE(ref.starts_with("adon"));
}

TEST(StringRefStartsWith, StdStringOverload) {
  StringRef ref("TP96", 4);
  EXPECT_TRUE(ref.starts_with(std::string("TP")));
  EXPECT_FALSE(ref.starts_with(std::string("96")));
}

TEST(StringRefStartsWith, RefOverloadComparesOnlyTheViewedLength) {
  // The prefix is a bounded view: bytes past its length must not be compared.
  StringRef ref("FR:123", 6);
  StringRef prefix("FR:xyz", 3);
  EXPECT_TRUE(ref.starts_with(prefix));
}

// The generated api messages start their encode only string fields as a null pointer with zero
// length; every member must treat that exactly like the default constructed empty string.
TEST(StringRefNullEmpty, BehavesAsEmptyString) {
  const StringRef null_empty{nullptr, 0};
  const StringRef empty;
  EXPECT_TRUE(null_empty.empty());
  EXPECT_EQ(null_empty.size(), 0u);
  EXPECT_EQ(null_empty.c_str(), nullptr);
  EXPECT_EQ(null_empty.byte(), nullptr);
  EXPECT_TRUE(null_empty == empty);
  EXPECT_FALSE(null_empty < empty);
  EXPECT_FALSE(empty < null_empty);
  EXPECT_TRUE(null_empty == "");             // NOLINT(readability-container-size-empty) - operator under test
  EXPECT_TRUE(null_empty == std::string());  // NOLINT(readability-container-size-empty) - operator under test
  EXPECT_EQ(null_empty.compare(empty), 0);
  EXPECT_EQ(null_empty.compare(""), 0);
  EXPECT_LT(null_empty.compare("a"), 0);
  EXPECT_TRUE(null_empty.starts_with(""));
  EXPECT_FALSE(null_empty.starts_with("a"));
  EXPECT_EQ(null_empty.str(), std::string());
  EXPECT_EQ(null_empty.substr(0), std::string());
  EXPECT_EQ(null_empty.find('a'), std::string::npos);
  EXPECT_EQ(null_empty.find("a"), std::string::npos);
  char buf[4] = "xyz";
  EXPECT_EQ(null_empty.copy(buf, sizeof(buf)), 0u);
  EXPECT_EQ(null_empty.begin(), null_empty.end());
}

TEST(StringRefNullEmpty, ComparesAgainstText) {
  const StringRef null_empty{nullptr, 0};
  const StringRef text("abc", 3);
  EXPECT_FALSE(null_empty == text);
  EXPECT_FALSE(text == null_empty);
  EXPECT_LT(null_empty.compare(text), 0);
  EXPECT_GT(text.compare(null_empty), 0);
  EXPECT_TRUE(null_empty < text);
  EXPECT_FALSE(text < null_empty);
  EXPECT_TRUE(text.starts_with(null_empty));
}

TEST(StringRefNullEmpty, TwoNullViewsAreEqual) {
  const StringRef a{nullptr, 0};
  const StringRef b{nullptr, 0};
  EXPECT_TRUE(a == b);
  EXPECT_FALSE(a < b);
  EXPECT_EQ(a.compare(b), 0);
  EXPECT_TRUE(a.starts_with(b));
}

// Every iterator endpoint of a null view is the same null position: nothing is dereferenced and
// no offset is applied to the null pointer, so the range is simply empty.
TEST(StringRefNullEmpty, IteratorEndpointsFormAnEmptyRange) {
  const StringRef null_empty{nullptr, 0};
  EXPECT_EQ(null_empty.cbegin(), null_empty.cend());
  EXPECT_EQ(null_empty.rbegin(), null_empty.rend());
  EXPECT_EQ(null_empty.crbegin(), null_empty.crend());
  EXPECT_EQ(std::distance(null_empty.begin(), null_empty.end()), 0);
  size_t visited = 0;
  for (char c : null_empty) {
    (void) c;
    visited++;
  }
  EXPECT_EQ(visited, 0u);
  // NOLINTNEXTLINE(bugprone-string-constructor) - empty range under test
  EXPECT_EQ(std::string(null_empty.begin(), null_empty.end()), std::string());
}

// The pointer and length constructor accepts an empty range at a null pointer; the copy into a
// std::string reads nothing.
TEST(StringRefNullEmpty, ConvertsToEmptyStdString) {
  const StringRef null_empty{nullptr, 0};
  const std::string copy = null_empty.str();
  EXPECT_TRUE(copy.empty());
  EXPECT_EQ(static_cast<std::string>(null_empty), std::string());
  EXPECT_EQ(null_empty.substr(0, 5), std::string());
  std::string target("keep");
  target += null_empty;
  EXPECT_EQ(target, "keep");
}

// The number conversions hand the pointer to the C library; a null view must stop before that.
TEST(StringRefNullEmpty, NumericConversionsReturnZero) {
  const StringRef null_empty{nullptr, 0};
  size_t pos = 99;
  EXPECT_EQ(stoi(null_empty, &pos), 0);
  EXPECT_EQ(pos, 0u);
  pos = 99;
  EXPECT_EQ(stol(null_empty, &pos, 16), 0L);
  EXPECT_EQ(pos, 0u);
  pos = 99;
  EXPECT_EQ(stof(null_empty, &pos), 0.0f);
  EXPECT_EQ(pos, 0u);
  pos = 99;
  EXPECT_EQ(stod(null_empty, &pos), 0.0);
  EXPECT_EQ(pos, 0u);
  EXPECT_EQ(stoi(null_empty), 0);
  EXPECT_EQ(stof(null_empty), 0.0f);
}

}  // namespace esphome::core::testing