Google Mock：测试对象的某个属性

Question

我尝试按照 Google Mock CookBook 中提供的示例定义自定义匹配器。

代码如下

    #include "gmock/gmock.h"
    #include "gtest/gtest.h"
    using namespace std;
    using ::testing::MatcherInterface;
    using ::testing::MatchResultListener;
    using ::testing::Matcher;
    using ::testing::_;
    using ::testing::AtLeast;
    using ::testing::Invoke;
    class Foo2;
    class Foo2
    {
        public:
            virtual int bar() const
            {
                return 4;
            }
            virtual int baz() const
            {
                return 5;
            }
            virtual void DoThis (Matcher<const Foo2&> pFunc)
          {
                     std::cout << "Foo:DoThis" << std::endl;
          }
          virtual void DoThat(int)
          {
                 std::cout << "Foo:DoThat" << std::endl;
          }
            virtual ~Foo2()
            {

            }

    };

    class BarPlusBazEqMatcher : public MatcherInterface<const Foo2&> {
     public:
      explicit BarPlusBazEqMatcher(int expected_sum)
          : expected_sum_(expected_sum) {}

      virtual bool MatchAndExplain(const Foo2& foo,
                                   MatchResultListener* listener) const {
        return (foo.bar() + foo.baz()) == expected_sum_;
      }

      virtual void DescribeTo(::std::ostream* os) const {
        *os << "bar() + baz() equals " << expected_sum_;
      }

      virtual void DescribeNegationTo(::std::ostream* os) const {
        *os << "bar() + baz() does not equal " << expected_sum_;
      }
      virtual ~BarPlusBazEqMatcher()
      {

      }

     private:
      const int expected_sum_;
    };


    inline Matcher<const Foo2&> BarPlusBazEq(int expected_sum) {
      return MakeMatcher(new BarPlusBazEqMatcher(expected_sum));
    }


    class MockFoo2 : public Foo2 {
     public:

      MOCK_METHOD1(DoThis,void(Matcher<const Foo2&>));
      MOCK_METHOD1(DoThat, void(int));
    };

    TEST(MockMatcher, Matcher)
    {
        MockFoo2 mockF;
        EXPECT_CALL(mockF, DoThis(BarPlusBazEq(5)));
    }

当我尝试编译上述代码时，却产生以下编译错误

*..\..gtest\gtest.h:9160:60: error: no match for 'operator==' (operand types are 'const testing::Matcher<const Foo2&>' and 'const testing::Matcher<const Foo2&>')
   bool operator()(const A& a, const B& b) const { return a == b; }*
                                                          ~~^~~~

*..\..gtest\gtest.h:14096:13: note: candidate: bool testing::internal::operator==(testing::internal::faketype, testing::internal::faketype)
 inline bool operator==(faketype, faketype) { return true; }*


*..\..gtest\gtest.h:14096:13: note:   no known conversion for argument 1 from 'const testing::Matcher<const Foo2&>' to 'testing::internal::faketype'*

如何解决这些错误？

Answer 1

匹配器应该只在你的测试方法中使用，而不是在类定义中。此示例中的BarPlusBazEq 期望匹配const &Foo2 类型的函数参数。所以DoThis()需要被定义为一个采用该参数类型的函数：

class Foo2 {
public:
    virtual int bar() const { return 4; }
    virtual int baz() const { return 5; }

    virtual void DoThis(const Foo2 &foo) {
        std::cout << "Foo2:DoThis" << std::endl;
    }
    virtual ~Foo2() {}
};

class MockFoo2 : public Foo2 {
public:
    MOCK_METHOD1(DoThis, void(const Foo2&));
};

class BarPlusBazEqMatcher : public MatcherInterface<const Foo2&> {
public:
    explicit BarPlusBazEqMatcher(int expected_sum)
        : expected_sum_(expected_sum) {}

    virtual bool MatchAndExplain(const Foo2& foo,
        MatchResultListener* listener) const {
        return (foo.bar() + foo.baz()) == expected_sum_;
    }

    virtual void DescribeTo(::std::ostream* os) const {
        *os << "bar() + baz() equals " << expected_sum_;
    }

    virtual void DescribeNegationTo(::std::ostream* os) const {
        *os << "bar() + baz() does not equal " << expected_sum_;
    }

    virtual ~BarPlusBazEqMatcher() {}

private:
    const int expected_sum_;
};

inline Matcher<const Foo2&> BarPlusBazEq(int expected_sum) {
    return MakeMatcher(new BarPlusBazEqMatcher(expected_sum));
}

TEST(MockMatcher, Matcher)
{
    MockFoo2 mock;
    EXPECT_CALL(mock, DoThis(BarPlusBazEq(9)));

    // You also have to do something to trigger the expected call...
    Foo2 foo2;
    mock.DoThis(foo2);
}

顺便说一句，您还可以避免定义完整接口的麻烦，并使用简单的custom matcher 完成同样的事情，如下所示：

MATCHER_P(BarPlusBazEq, expected_sum, "") { return arg.bar() + arg.baz() == expected_sum; }