GTEST/GMOCK介绍与实战：Gtest Sample3

1.简介

示例#3使用测试fixture(固定)

2.用法

CMakeLists.txt

cmake_minimum_required(VERSION 3.0.0)
project(hello_gtest VERSION 0.1.0)

add_executable(${PROJECT_NAME} main.cc sample.cc sample_unitest.cc)
target_link_libraries(${PROJECT_NAME} gtest pthread)

main.cc

#include <gtest/gtest.h>

int main(int argc,  char *argv[])
{
    testing::InitGoogleTest(&argc, argv);
    return RUN_ALL_TESTS();
}

sample.h

// A sample program demonstrating using Google C++ testing framework.

#ifndef GOOGLETEST_SAMPLES_SAMPLE3_INL_H_
#define GOOGLETEST_SAMPLES_SAMPLE3_INL_H_

#include <stddef.h>


// Queue is a simple queue implemented as a singled-linked list.
//
// The element type must support copy constructor.
template <typename E>  // E is the element type
class Queue;

// QueueNode is a node in a Queue, which consists of an element of
// type E and a pointer to the next node.
template <typename E>  // E is the element type
class QueueNode {
  friend class Queue<E>;

 public:
  // Gets the element in this node.
  const E& element() const { return element_; }

  // Gets the next node in the queue.
  QueueNode* next() { return next_; }
  const QueueNode* next() const { return next_; }

 private:
  // Creates a node with a given element value.  The next pointer is
  // set to NULL.
  explicit QueueNode(const E& an_element)
      : element_(an_element), next_(nullptr) {}

  // We disable the default assignment operator and copy c'tor.
  const QueueNode& operator = (const QueueNode&);
  QueueNode(const QueueNode&);

  E element_;
  QueueNode* next_;
};

template <typename E>  // E is the element type.
class Queue {
 public:
  // Creates an empty queue.
  Queue() : head_(nullptr), last_(nullptr), size_(0) {}

  // D'tor.  Clears the queue.
  ~Queue() { Clear(); }

  // Clears the queue.
  void Clear() {
    if (size_ > 0) {
      // 1. Deletes every node.
      QueueNode<E>* node = head_;
      QueueNode<E>* next = node->next();
      for (; ;) {
        delete node;
        node = next;
        if (node == nullptr) break;
        next = node->next();
      }

      // 2. Resets the member variables.
      head_ = last_ = nullptr;
      size_ = 0;
    }
  }

  // Gets the number of elements.
  size_t Size() const { return size_; }

  // Gets the first element of the queue, or NULL if the queue is empty.
  QueueNode<E>* Head() { return head_; }
  const QueueNode<E>* Head() const { return head_; }

  // Gets the last element of the queue, or NULL if the queue is empty.
  QueueNode<E>* Last() { return last_; }
  const QueueNode<E>* Last() const { return last_; }

  // Adds an element to the end of the queue.  A copy of the element is
  // created using the copy constructor, and then stored in the queue.
  // Changes made to the element in the queue doesn't affect the source
  // object, and vice versa.
  void Enqueue(const E& element) {
    QueueNode<E>* new_node = new QueueNode<E>(element);

    if (size_ == 0) {
      head_ = last_ = new_node;
      size_ = 1;
    } else {
      last_->next_ = new_node;
      last_ = new_node;
      size_++;
    }
  }

  // Removes the head of the queue and returns it.  Returns NULL if
  // the queue is empty.
  E* Dequeue() {
    if (size_ == 0) {
      return nullptr;
    }

    const QueueNode<E>* const old_head = head_;
    head_ = head_->next_;
    size_--;
    if (size_ == 0) {
      last_ = nullptr;
    }

    E* element = new E(old_head->element());
    delete old_head;

    return element;
  }

  // Applies a function/functor on each element of the queue, and
  // returns the result in a new queue.  The original queue is not
  // affected.
  template <typename F>
  Queue* Map(F function) const {
    Queue* new_queue = new Queue();
    for (const QueueNode<E>* node = head_; node != nullptr;
         node = node->next_) {
      new_queue->Enqueue(function(node->element()));
    }

    return new_queue;
  }

 private:
  QueueNode<E>* head_;  // The first node of the queue.
  QueueNode<E>* last_;  // The last node of the queue.
  size_t size_;  // The number of elements in the queue.

  // We disallow copying a queue.
  Queue(const Queue&);
  const Queue& operator = (const Queue&);
};

#endif  // GOOGLETEST_SAMPLES_SAMPLE3_INL_H_

sample_unitest.cc

首先声明了一个 test fixture 类，在这个类中实现了一些测试时用到的辅助函数，以及使用SetUp预置了一些测试数据。（除了有特殊需求，则不需要实现TearDown，因为析构函数已经帮我们释放了资源）

// A sample program demonstrating using Google C++ testing framework.

// In this example, we use a more advanced feature of Google Test called
// test fixture.
//
// A test fixture is a place to hold objects and functions shared by
// all tests in a test case.  Using a test fixture avoids duplicating
// the test code necessary to initialize and cleanup those common
// objects for each test.  It is also useful for defining sub-routines
// that your tests need to invoke a lot.
//
// <TechnicalDetails>
//
// The tests share the test fixture in the sense of code sharing, not
// data sharing.  Each test is given its own fresh copy of the
// fixture.  You cannot expect the data modified by one test to be
// passed on to another test, which is a bad idea.
//
// The reason for this design is that tests should be independent and
// repeatable.  In particular, a test should not fail as the result of
// another test's failure.  If one test depends on info produced by
// another test, then the two tests should really be one big test.
//
// The macros for indicating the success/failure of a test
// (EXPECT_TRUE, FAIL, etc) need to know what the current test is
// (when Google Test prints the test result, it tells you which test
// each failure belongs to).  Technically, these macros invoke a
// member function of the Test class.  Therefore, you cannot use them
// in a global function.  That's why you should put test sub-routines
// in a test fixture.
//
// </TechnicalDetails>

#include "sample3-inl.h"
#include "gtest/gtest.h"
namespace {
// To use a test fixture, derive a class from testing::Test.
class QueueTestSmpl3 : public testing::Test {
 protected:  // You should make the members protected s.t. they can be
             // accessed from sub-classes.

  // virtual void SetUp() will be called before each test is run.  You
  // should define it if you need to initialize the variables.
  // Otherwise, this can be skipped.
  void SetUp() override {
    q1_.Enqueue(1);
    q2_.Enqueue(2);
    q2_.Enqueue(3);
  }

  // virtual void TearDown() will be called after each test is run.
  // You should define it if there is cleanup work to do.  Otherwise,
  // you don't have to provide it.
  //
  // virtual void TearDown() {
  // }

  // A helper function that some test uses.
  static int Double(int n) {
    return 2*n;
  }

  // A helper function for testing Queue::Map().
  void MapTester(const Queue<int> * q) {
    // Creates a new queue, where each element is twice as big as the
    // corresponding one in q.
    const Queue<int> * const new_q = q->Map(Double);

    // Verifies that the new queue has the same size as q.
    ASSERT_EQ(q->Size(), new_q->Size());

    // Verifies the relationship between the elements of the two queues.
    for (const QueueNode<int>*n1 = q->Head(), *n2 = new_q->Head();
         n1 != nullptr; n1 = n1->next(), n2 = n2->next()) {
      EXPECT_EQ(2 * n1->element(), n2->element());
    }

    delete new_q;
  }

  // Declares the variables your tests want to use.
  Queue<int> q0_;
  Queue<int> q1_;
  Queue<int> q2_;
};

// When you have a test fixture, you define a test using TEST_F
// instead of TEST.

// Tests the default c'tor.
TEST_F(QueueTestSmpl3, DefaultConstructor) {
  // You can access data in the test fixture here.
  EXPECT_EQ(0u, q0_.Size());
}

// Tests Dequeue().
TEST_F(QueueTestSmpl3, Dequeue) {
  int * n = q0_.Dequeue();
  EXPECT_TRUE(n == nullptr);

  n = q1_.Dequeue();
  ASSERT_TRUE(n != nullptr);
  EXPECT_EQ(1, *n);
  EXPECT_EQ(0u, q1_.Size());
  delete n;

  n = q2_.Dequeue();
  ASSERT_TRUE(n != nullptr);
  EXPECT_EQ(2, *n);
  EXPECT_EQ(1u, q2_.Size());
  delete n;
}

// Tests the Queue::Map() function.
TEST_F(QueueTestSmpl3, Map) {
  MapTester(&q0_);
  MapTester(&q1_);
  MapTester(&q2_);
}
}  // namespace

这里以 DefaultConstructor 为例，来分析一下它的执行流程：

QueueTestSmpl3 调用构造函数，构造对象。
QueueTestSmpl3 对象调用 SetUp 函数初始化测试配置。
DefaultConstructor 开始执行并结束测试。
QueueTestSmpl3 对象调用隐式生成的 TearDown 进行清理。
QueueTestSmpl3 调用析构函数，析构对象。

• ref：gtest sample

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