googletest：sample6分析

待测文件

PrimeTable类声明了素数表的一系列接口，包括
1）IsPrime：判断当前输入数n是否为素数；
2）GetNextPrime：找比输入数n大的下一个素数.

prime_tables.h

#include <algorithm>

// The prime table interface.
class PrimeTable {
 public:
  virtual ~PrimeTable() = default;

  // Returns true if and only if n is a prime number.
  virtual bool IsPrime(int n) const = 0;

  // Returns the smallest prime number greater than p; or returns -1
  // if the next prime is beyond the capacity of the table.
  virtual int GetNextPrime(int p) const = 0;
};

派生类OnTheFlyPrimeTable实现了PrimeTable接口，基于当前输入数进行实时计算.

// Implementation #1 calculates the primes on-the-fly.
class OnTheFlyPrimeTable : public PrimeTable {
 public:
  bool IsPrime(int n) const override {
    if (n <= 1) return false;

    for (int i = 2; i * i <= n; i++) {
      // n is divisible by an integer other than 1 and itself.
      if ((n % i) == 0) return false;
    }

    return true;
  }

  int GetNextPrime(int p) const override {
    if (p < 0) return -1;

    for (int n = p + 1;; n++) {
      if (IsPrime(n)) return n;
    }
  }
};

派生类PreCalculatedPrimeTable实现了PrimeTable接口，不过多了一个数组is_prime_[0..is_prime_size_-1]用于记录已经判断过的数是否为素数. 数组缓存大小由用户在构建对象时指定.

// Implementation #2 pre-calculates the primes and stores the result
// in an array.
class PreCalculatedPrimeTable : public PrimeTable {
 public:
  // 'max' specifies the maximum number the prime table holds.
  explicit PreCalculatedPrimeTable(int max)
      : is_prime_size_(std::max(1, max + 1)),
        is_prime_(new bool[static_cast<size_t>(is_prime_size_)]) {
    CalculatePrimesUpTo(is_prime_size_ - 1);
  }
  ~PreCalculatedPrimeTable() override { delete[] is_prime_; }

  bool IsPrime(int n) const override {
    return 0 <= n && n < is_prime_size_ && is_prime_[n];
  }

  int GetNextPrime(int p) const override {
    for (int n = p + 1; n < is_prime_size_; n++) {
      if (is_prime_[n]) return n;
    }

    return -1;
  }

 private:
  void CalculatePrimesUpTo(int max) {
    ::std::fill(is_prime_, is_prime_ + is_prime_size_, true);
    is_prime_[0] = is_prime_[1] = false;

    // Checks every candidate for prime number (we know that 2 is the only even
    // prime).
    for (int i = 2; i * i <= max; i += i % 2 + 1) {
      if (!is_prime_[i]) continue;

      // Marks all multiples of i (except i itself) as non-prime.
      // We are starting here from i-th multiplier, because all smaller
      // complex numbers were already marked.
      for (int j = i * i; j <= max; j += i) {
        is_prime_[j] = false;
      }
    }
  }

  const int is_prime_size_;
  bool* const is_prime_;

  // Disables compiler warning "assignment operator could not be generated."
  void operator=(const PreCalculatedPrimeTable& rhs);
};

测试文件

对于测试这种同一个父类的派生类，能否复用测试？
googletest提供了2种方法：

"typed test"：类型测试. 要求写测试时，已知所有类型；
"type-parameterized tests"：类型参数化测试. 写测试时，不必知晓所有类型，只需要知道接口即可.

共同步骤：

首先，我们通过模板的特例化定义工厂方法，用于创建待测的类对象OnTheFlyPrimeTable, PreCalculatedPrimeTable，如果有一些对象初值，也可以在这一步构造时传入；

接着，定义测试夹具类模板PrimeTableTest，利用夹具类实现测试时自动创建、析构待测类对象.

sample6_unittest.cc

// First, we define some factory functions for creating instances of
// the implementations.  You may be able to skip this step if all your
// implementations can be constructed the same way.

template <class T>
PrimeTable* CreatePrimeTable();

template <>
PrimeTable* CreatePrimeTable<OnTheFlyPrimeTable>() {
  return new OnTheFlyPrimeTable;
}

template <>
PrimeTable* CreatePrimeTable<PreCalculatedPrimeTable>() {
  return new PreCalculatedPrimeTable(10000);
}

// Then we define a test fixture class template.
template <class T>
class PrimeTableTest : public testing::Test {
 protected:
  // The ctor calls the factory function to create a prime table
  // implemented by T.
  PrimeTableTest() : table_(CreatePrimeTable<T>()) {}

  ~PrimeTableTest() override { delete table_; }

  // Note that we test an implementation via the base interface
  // instead of the actual implementation class.  This is important
  // for keeping the tests close to the real world scenario, where the
  // implementation is invoked via the base interface.  It avoids
  // got-yas where the implementation class has a method that shadows
  // a method with the same name (but slightly different argument
  // types) in the base interface, for example.
  PrimeTable* const table_;
};

对于方法1（"typed test"）：

1）需要先定义我们想要测试的所有类型的列表，形如typedef Types<type1, type2, ...> MyTypeList；

2）然后用TYPED_TEST_SUITE 定义类型化的测试组件；

3）最后用TYPED_TEST定义类型化的测试用例；

tips：TYPED_TEST_SUITE(TestCaseName, TypeList)定义类型化的测试组件，TestCaseName必须匹配测试夹具名，TypeList是前面用typedef定义的类型列表；

TYPED_TEST(TestCaseName, TestName)定义类型化的测试用例，功能类似于TEST_F，TestCaseName必须匹配测试夹具名，TestName是我们针对每个测试自定义的测试名.

"typed test"：

using testing::Types;

// Google Test offers two ways for reusing tests for different types.
// The first is called "typed tests".  You should use it if you
// already know *all* the types you are gonna exercise when you write
// the tests.

// To write a typed test case, first use
//
//   TYPED_TEST_SUITE(TestCaseName, TypeList);
//
// to declare it and specify the type parameters.  As with TEST_F,
// TestCaseName must match the test fixture name.

// The list of types we want to test.
typedef Types<OnTheFlyPrimeTable, PreCalculatedPrimeTable> Implementations;

TYPED_TEST_SUITE(PrimeTableTest, Implementations);

// Then use TYPED_TEST(TestCaseName, TestName) to define a typed test,
// similar to TEST_F.
TYPED_TEST(PrimeTableTest, ReturnsFalseForNonPrimes) {
  // Inside the test body, you can refer to the type parameter by
  // TypeParam, and refer to the fixture class by TestFixture.  We
  // don't need them in this example.

  // Since we are in the template world, C++ requires explicitly
  // writing 'this->' when referring to members of the fixture class.
  // This is something you have to learn to live with.
  EXPECT_FALSE(this->table_->IsPrime(-5));
  EXPECT_FALSE(this->table_->IsPrime(0));
  EXPECT_FALSE(this->table_->IsPrime(1));
  EXPECT_FALSE(this->table_->IsPrime(4));
  EXPECT_FALSE(this->table_->IsPrime(6));
  EXPECT_FALSE(this->table_->IsPrime(100));
}

TYPED_TEST(PrimeTableTest, ReturnsTrueForPrimes) {
  EXPECT_TRUE(this->table_->IsPrime(2));
  EXPECT_TRUE(this->table_->IsPrime(3));
  EXPECT_TRUE(this->table_->IsPrime(5));
  EXPECT_TRUE(this->table_->IsPrime(7));
  EXPECT_TRUE(this->table_->IsPrime(11));
  EXPECT_TRUE(this->table_->IsPrime(131));
}

TYPED_TEST(PrimeTableTest, CanGetNextPrime) {
  EXPECT_EQ(2, this->table_->GetNextPrime(0));
  EXPECT_EQ(3, this->table_->GetNextPrime(2));
  EXPECT_EQ(5, this->table_->GetNextPrime(3));
  EXPECT_EQ(7, this->table_->GetNextPrime(5));
  EXPECT_EQ(11, this->table_->GetNextPrime(7));
  EXPECT_EQ(131, this->table_->GetNextPrime(128));
}

// That's it!  Google Test will repeat each TYPED_TEST for each type
// in the type list specified in TYPED_TEST_SUITE.  Sit back and be
// happy that you don't have to define them multiple times.

注意：因为在模板中，C++在引用fixture类成员时，需要显式地加上this->.

对于方法2（"type-parameterized tests"）：

1）用TYPED_TEST_SUITE_P声明测试用例. 参数名是测试夹具名称，也通常是测试用例的名称. 后缀名_P表示参数化（"parameterized"）或模式（"pattern"）；
2）用TYPED_TEST_P定义测试，类似于TEST_F；
3）用REGISTER_TYPED_TEST_SUITE_P枚举前面定义的测试. 到这一步，已经完成了测试模式，不过没有真正执行具体的测试，还没给类型参数；
4）用INSTANTIATE_TYPED_TEST_SUITE_P实例化类型参数测试，需要指定类型列表.

using testing::Types;

// Sometimes, however, you don't yet know all the types that you want
// to test when you write the tests.  For example, if you are the
// author of an interface and expect other people to implement it, you
// might want to write a set of tests to make sure each implementation
// conforms to some basic requirements, but you don't know what
// implementations will be written in the future.
//
// How can you write the tests without committing to the type
// parameters?  That's what "type-parameterized tests" can do for you.
// It is a bit more involved than typed tests, but in return you get a
// test pattern that can be reused in many contexts, which is a big
// win.  Here's how you do it:

// First, define a test fixture class template.  Here we just reuse
// the PrimeTableTest fixture defined earlier:

template <class T>
class PrimeTableTest2 : public PrimeTableTest<T> {};

// Then, declare the test case.  The argument is the name of the test
// fixture, and also the name of the test case (as usual).  The _P
// suffix is for "parameterized" or "pattern".
TYPED_TEST_SUITE_P(PrimeTableTest2);

// Next, use TYPED_TEST_P(TestCaseName, TestName) to define a test,
// similar to what you do with TEST_F.
TYPED_TEST_P(PrimeTableTest2, ReturnsFalseForNonPrimes) {
  EXPECT_FALSE(this->table_->IsPrime(-5));
  EXPECT_FALSE(this->table_->IsPrime(0));
  EXPECT_FALSE(this->table_->IsPrime(1));
  EXPECT_FALSE(this->table_->IsPrime(4));
  EXPECT_FALSE(this->table_->IsPrime(6));
  EXPECT_FALSE(this->table_->IsPrime(100));
}

TYPED_TEST_P(PrimeTableTest2, ReturnsTrueForPrimes) {
  EXPECT_TRUE(this->table_->IsPrime(2));
  EXPECT_TRUE(this->table_->IsPrime(3));
  EXPECT_TRUE(this->table_->IsPrime(5));
  EXPECT_TRUE(this->table_->IsPrime(7));
  EXPECT_TRUE(this->table_->IsPrime(11));
  EXPECT_TRUE(this->table_->IsPrime(131));
}

TYPED_TEST_P(PrimeTableTest2, CanGetNextPrime) {
  EXPECT_EQ(2, this->table_->GetNextPrime(0));
  EXPECT_EQ(3, this->table_->GetNextPrime(2));
  EXPECT_EQ(5, this->table_->GetNextPrime(3));
  EXPECT_EQ(7, this->table_->GetNextPrime(5));
  EXPECT_EQ(11, this->table_->GetNextPrime(7));
  EXPECT_EQ(131, this->table_->GetNextPrime(128));
}

// Type-parameterized tests involve one extra step: you have to
// enumerate the tests you defined:
REGISTER_TYPED_TEST_SUITE_P(
    PrimeTableTest2,  // The first argument is the test case name.
    // The rest of the arguments are the test names.
    ReturnsFalseForNonPrimes, ReturnsTrueForPrimes, CanGetNextPrime);

// At this point the test pattern is done.  However, you don't have
// any real test yet as you haven't said which types you want to run
// the tests with.

// To turn the abstract test pattern into real tests, you instantiate
// it with a list of types.  Usually the test pattern will be defined
// in a .h file, and anyone can #include and instantiate it.  You can
// even instantiate it more than once in the same program.  To tell
// different instances apart, you give each of them a name, which will
// become part of the test case name and can be used in test filters.

// The list of types we want to test.  Note that it doesn't have to be
// defined at the time we write the TYPED_TEST_P()s.
typedef Types<OnTheFlyPrimeTable, PreCalculatedPrimeTable>
    PrimeTableImplementations;
INSTANTIATE_TYPED_TEST_SUITE_P(OnTheFlyAndPreCalculated,    // Instance name
                               PrimeTableTest2,             // Test case name
                               PrimeTableImplementations);  // Type list

小结

对于派生类，或者实现同一接口的类，有两种方式可以复用test：

typed test;
type-parameterized tests.

如果已知要测试的派生类类型，可用第一种；如果还在设计阶段，或者派生类类型未知，可用第二种.

posted @ 2025-02-28 21:59 明明1109 阅读(32) 评论(0) 收藏举报

刷新页面返回顶部

明明1109

googletest：sample6分析

目录

待测文件

测试文件

小结

公告