Google单元测试sample分析（三）

本文介绍关于模版类该如何设置单元测试

源码目录在googletest/googletest/目录下的prime_tables.h和sample6_unittest.cc

prime_tables.h

// Copyright 2008 Google Inc.
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// This provides interface PrimeTable that determines whether a number is a
// prime and determines a next prime number. This interface is used
// in Google Test samples demonstrating use of parameterized tests.

#ifndef GTEST_SAMPLES_PRIME_TABLES_H_
#define GTEST_SAMPLES_PRIME_TABLES_H_

#include 

// The prime table interface.
class PrimeTable {
 public:
  virtual ~PrimeTable() {}

  // 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;
};

// 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 {
    for (int n = p + 1; n > 0; n++) {
      if (IsPrime(n)) return n;
    }

    return -1;
  }
};

// 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_(max + 1), is_prime_(new bool[max + 1]) {
    CalculatePrimesUpTo(max);
  }
  ~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);
};

#endif  // GTEST_SAMPLES_PRIME_TABLES_H_

该文件定义了一个抽象类PrimeTable ，OnTheFlyPrimeTable 和PreCalculatedPrimeTable 分别实现该类。

sample6_unittest.cc

#include "prime_tables.h"

#include "gtest/gtest.h"
namespace {
// 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_;
};

#if GTEST_HAS_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.

#endif  // GTEST_HAS_TYPED_TEST

以上代码中PrimeTableTest类继承自testing::Test，类内部定义个PrimeTable类型指针。

如下是Google Test框架中的Typed Test（带类型的测试）功能，在testing::Types命名空间中

#if GTEST_HAS_TYPED_TEST
using testing::Types;

如下Implementations是一个模板参数，它包含了两种实现的类型。
typedef Types Implementations;

TYPED_TEST_SUITE(PrimeTableTest, Implementations);

最后运行结果如下：

可以看出PrimeTableTest测试夹具中，针对OnTheFlyPrimeTable和PreCalculatedPrimeTable两种类型都测试一次。

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));
}

运行结果：