TEST(FactorialTest, Negative) {
  // This test is named "Negative", and belongs to the "FactorialTest"
  // test case.
  EXPECT_EQ(1, Factorial(-5));
  EXPECT_EQ(1, Factorial(-10));
  EXPECT_GT(Factorial(-10), 0);
}
​
// Tests factorial of 0.
TEST(FactorialTest, Zero) { EXPECT_EQ(1, Factorial(0)); }
​
// Tests factorial of positive numbers.
TEST(FactorialTest, Positive) {
  EXPECT_EQ(1, Factorial(1));
  EXPECT_EQ(2, Factorial(2));
  EXPECT_EQ(6, Factorial(3));
  EXPECT_EQ(40320, Factorial(8));
}

// Tests negative input.
TEST(IsPrimeTest, Negative) {
  // This test belongs to the IsPrimeTest test case.
​
  EXPECT_FALSE(IsPrime(-1));
  EXPECT_FALSE(IsPrime(-2));
  EXPECT_FALSE(IsPrime(INT_MIN));
}
​
// Tests some trivial cases.
TEST(IsPrimeTest, Trivial) {
  EXPECT_FALSE(IsPrime(0));
  EXPECT_FALSE(IsPrime(1));
  EXPECT_TRUE(IsPrime(2));
  EXPECT_TRUE(IsPrime(3));
}
​
// Tests positive input.
TEST(IsPrimeTest, Positive) {
  EXPECT_FALSE(IsPrime(4));
  EXPECT_TRUE(IsPrime(5));
  EXPECT_FALSE(IsPrime(6));
  EXPECT_TRUE(IsPrime(23));
}

int main(int argc, char* argv[]) {
  cout << "start gtest demo \r\n" << endl;
  ::testing::InitGoogleTest(&argc, argv);
  return RUN_ALL_TESTS();
}

class MyString {
 private:
  const char* c_string_;
  const MyString& operator=(const MyString& rhs);
​
 public:
  // Clones a 0-terminated C string, allocating memory using new.
  // 類方法
  static const char* CloneCString(const char* a_c_string);
​
  // The default c'tor constructs a NULL string. 
  // 默認構造函數
  MyString() : c_string_(nullptr) {}
​
  // Constructs a MyString by cloning a 0-terminated C string. 
  // 構造函數，禁止隱式轉換
  explicit MyString(const char* a_c_string) : c_string_(nullptr) {
    Set(a_c_string);
  }
​
  // Copy c'tor
  // 拷貝構造函數
  MyString(const MyString& string) : c_string_(nullptr) {
    Set(string.c_string_);
  }
​
  // D'tor.  MyString is intended to be a final class, so the d'tor
  // doesn't need to be virtual.
  ~MyString() { delete[] c_string_; }
​
  // Gets the 0-terminated C string this MyString object represents.
  const char* c_string() const { return c_string_; }
​
  size_t Length() const { return c_string_ == nullptr ? 0 : strlen(c_string_); }
​
  // Sets the 0-terminated C string this MyString object represents.
  // 成員函數
  void Set(const char* c_string);
};

// Clones a 0-terminated C string, allocating memory using new.
const char* MyString::CloneCString(const char* a_c_string) {
  if (a_c_string == nullptr) return nullptr;
​
  const size_t len = strlen(a_c_string);
  char* const clone = new char[ len + 1 ];
  memcpy(clone, a_c_string, len + 1);
​
  return clone;
}
​
// Sets the 0-terminated C string this MyString object
// represents.
void MyString::Set(const char* a_c_string) {
  // Makes sure this works when c_string == c_string_
  const char* const temp = MyString::CloneCString(a_c_string);
  delete[] c_string_;
  c_string_ = temp;
}

  const MyString s;
  EXPECT_STREQ(nullptr, s.c_string());
  EXPECT_EQ(0u, s.Length());

const char kHelloString[] = "Hello, world!";
​
// Tests the c'tor that accepts a C string.
TEST(MyString, ConstructorFromCString) {
  const MyString s(kHelloString);
  EXPECT_EQ(0, strcmp(s.c_string(), kHelloString));
  EXPECT_EQ(sizeof(kHelloString)/sizeof(kHelloString[0]) - 1,
            s.Length());
}

// Tests the copy c'tor.
TEST(MyString, CopyConstructor) {
  const MyString s1(kHelloString);
  const MyString s2 = s1;
  EXPECT_EQ(0, strcmp(s2.c_string(), kHelloString));
}

// Tests the Set method.
TEST(MyString, Set) {
  MyString s;
​
  s.Set(kHelloString);
  EXPECT_EQ(0, strcmp(s.c_string(), kHelloString));
​
  // Set should work when the input pointer is the same as the one
  // already in the MyString object.
  s.Set(s.c_string());
  EXPECT_EQ(0, strcmp(s.c_string(), kHelloString));
​
  // Can we set the MyString to NULL?
  s.Set(nullptr);
  EXPECT_STREQ(nullptr, s.c_string());
}

  void SetUp() override {
    std::cout << "this test fixture" << std::endl;
    q1_.Enqueue(1);
    q2_.Enqueue(2);
    q2_.Enqueue(3);
  }

// Tests Dequeue().
TEST_F(QueueTestSmpl3, Dequeue) {
  int * n = q0_.Dequeue(); // q0 隊列沒有任何元素，setup沒有設置q0，出隊只會是nullptr
  EXPECT_TRUE(n == nullptr);
​
  n = q1_.Dequeue(); // q1 對列有一個元素：1
  ASSERT_TRUE(n != nullptr);
  EXPECT_EQ(1, *n);
  EXPECT_EQ(0u, q1_.Size()); // 出隊後，q1隊列沒有元素了
  delete n;
​
  n = q2_.Dequeue(); // q2在setup時候輸入了2,3兩個元素
  ASSERT_TRUE(n != nullptr);
  EXPECT_EQ(2, *n);
  EXPECT_EQ(1u, q2_.Size());
  delete n;
}

TEST(Counter, Increment) {
  Counter c;
​
  // Test that counter 0 returns 0
  EXPECT_EQ(0, c.Decrement());
​
  // EXPECT_EQ() evaluates its arguments exactly once, so they
  // can have side effects.
  EXPECT_EQ(0, c.Increment());
  EXPECT_EQ(1, c.Increment());
  EXPECT_EQ(2, c.Increment());
​
  EXPECT_EQ(3, c.Decrement());
}

int Counter::Increment() {
  return counter_++;
}

class IntegerFunctionTest : public QuickTest {
  // We don't need any more logic than already in the QuickTest fixture.
  // Therefore the body is empty.
};
TEST_F(IntegerFunctionTest, Factorial) {
    // **** 階乘函數的tests
}
​
TEST_F(IntegerFunctionTest, IsPrime) {
     // **** 判斷素數函數的tests
}

class QueueTest : public QuickTest {
 protected:
  void SetUp() override {
    // First, we need to set up the super fixture (QuickTest).
    QuickTest::SetUp();
​
    // Second, some additional setup for this fixture.
    q1_.Enqueue(1);
    q2_.Enqueue(2);
    q2_.Enqueue(3);
  }
​
  // By default, TearDown() inherits the behavior of
  // QuickTest::TearDown().  As we have no additional cleaning work
  // for QueueTest, we omit it here.
  //
  // virtual void TearDown() {
  //   QuickTest::TearDown();
  // }
​
  Queue<int> q0_;
  Queue<int> q1_;
  Queue<int> q2_;
};