GMock使用问题：TIMES报错、Mock行为修改及测试失败排查

待Mock的基类与Mock类定义 #

基类代码：

class Base{
public:
void virtual func() { sleep(3); }
};

Mock类代码：

class Mock: public Base{
public:
MOCK_METHOD(void, func, (), (override));
};

测试用例代码：

TEST(TestMockSanity, AbleToMock) {                                                        
Mock mock;                                                                    
EXPECT_CALL(mock, func());   
}                                                        

问题1：语法错误：class testing::internal::TypedExpectation<void()> has no member named ‘TIMES’ #

解决方法：

• TIMES是GMock的约束宏，需通过testing::Times()方式调用，正确链式写法示例：

  EXPECT_CALL(mock, func()).Times(testing::AtLeast(1));
  

• 注意：必须使用testing::命名空间下首字母大写的Times，而非全大写的TIMES，否则会触发语法错误。

问题2：如何将Mock类中func的实现改为sleep(0)？ #

推荐解决方法：使用ON_CALL设置默认行为，既保留Mock的验证能力，又自定义实现：

TEST(TestMockSanity, AbleToMock) {
    Mock mock;
    ON_CALL(mock, func()).WillByDefault([](){ sleep(0); });
    // 若需验证调用，可保留EXPECT_CALL
    EXPECT_CALL(mock, func());
    mock.func();
}

也可在Mock类中直接重写，但会失去Mock的灵活性，仅适合固定默认场景：

class Mock: public Base{
public:
    MOCK_METHOD(void, func, (), (override));
    void func() override {
        sleep(0);
    }
};

相关代码文件 #

./real.hpp #

class Real {
 public:
  Real(){};
  virtual ~Real(){};
  virtual int run();
  virtual int dont_run();
};

./real.cpp #

#include "real.hpp"

int Real::run() { return 0; };
int Real::dont_run() { return 1; };

./meson.build #

project(
  'gtest',
  'cpp',
  default_options : [
    'cpp_std=c++14',
  ],
)

sources = files('main.cpp', 'real.cpp')

executable(
  'real',
  sources,
  install : false,
)

executable(
  'mock',
  files('real.cpp', 'mock.cpp'),
  dependencies: [dependency('gtest'), dependency('gmock')],
  install : false,
)

./mock.cpp #

#include "gmock/gmock.h"  // MOCK_METHOD
#include "gtest/gtest.h"  // TEST
#include "real.hpp"

class MockReal : public Real {
 public:
  MOCK_METHOD(int, run, (), (override));
  MOCK_METHOD(int, dont_run, (), (override));

  void delegate(){
      ON_CALL(*this, run).WillByDefault([this](){
          return 1;
      });
      ON_CALL(*this, dont_run).WillByDefault([this](){
          return 2;
      });
  }
};

TEST(TestMockSanity, AbleToMock) {
  MockReal mock;

  EXPECT_EQ(0, mock.run());
  EXPECT_EQ(1, mock.dont_run());

  mock.delegate();

  EXPECT_EQ(1, mock.run());
  EXPECT_EQ(2, mock.dont_run());
}

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

测试运行结果 #

[==========] Running 1 test from 1 test suite.
[----------] Global test environment set-up.
[----------] 1 test from TestMockSanity
[ RUN      ] TestMockSanity.AbleToMock

GMOCK WARNING:
Uninteresting mock function call - returning default value.
    Function call: run()
          Returns: 0
NOTE: You can safely ignore the above warning unless this call should not happen.  Do not suppress it by blindly adding an EXPECT_CALL() if you don't mean to enforce the call.  See https://github.com/google/googletest/blob/master/docs/gmock_cook_book.md#knowing-when-to-expect for details.

GMOCK WARNING:
Uninteresting mock function call - returning default value.
    Function call: dont_run()
          Returns: 0
NOTE: You can safely ignore the above warning unless this call should not happen.  Do not suppress it by blindly adding an EXPECT_CALL() if you don't mean to enforce the call.  See https://github.com/google/googletest/blob/master/docs/gmock_cook_book.md#knowing-when-to-expect for details.
../mock.cpp:24: Failure
Expected equality of these values:
  1
  mock.dont_run()
    Which is: 0

GMOCK WARNING:
Uninteresting mock function call - taking default action specified at:
../mock.cpp:11:
    Function call: run()
          Returns: 1
NOTE: You can safely ignore the above warning unless this call should not happen.  Do not suppress it by blindly adding an EXPECT_CALL() if you don't mean to enforce the call.  See https://github.com/google/googletest/blob/master/docs/gmock_cook_book.md#knowing-when-to-expect for details.

GMOCK WARNING:
Uninteresting mock function call - taking default action specified at:
../mock.cpp:14:
    Function call: dont_run()
          Returns: 2
NOTE: You can safely ignore the above warning unless this call should not happen.  Do not suppress it by blindly adding an EXPECT_CALL() if you don't mean to enforce the call.  See https://github.com/google/googletest/blob/master/docs/gmock_cook_book.md#knowing-when-to-expect for details.
[  FAILED  ] TestMockSanity.AbleToMock (0 ms)
[----------] 1 test from TestMockSanity (0 ms total)

[----------] Global test environment tear-down
[==========] 1 test from 1 test suite ran. (0 ms total)
[  PASSED  ] 0 tests.
[  FAILED  ] 1 test, listed below:
[  FAILED  ] TestMockSanity.AbleToMock

 1 FAILED TEST

问题原因与解决方法 #

核心问题分析 #

1. Mock默认行为未调用基类方法：GMock覆盖基类虚函数后，默认返回类型的默认值（int类型返回0），而非调用基类dont_run()的返回值1，导致断言失败。
2. 构建配置符号冲突：meson.build中mock可执行文件同时链接real.cpp和mock.cpp，真实实现与Mock方法符号冲突，导致Mock机制无法正常工作。

解决步骤 #

1. 修改Mock类，默认调用基类实现：
   在Mock类构造函数中设置默认行为为调用基类方法，满足测试预期：

   class MockReal : public Real {
    public:
     MOCK_METHOD(int, run, (), (override));
     MOCK_METHOD(int, dont_run, (), (override));
   
     MockReal() {
         // 默认调用基类方法
         ON_CALL(*this, run).WillByDefault([this](){ return Real::run(); });
         ON_CALL(*this, dont_run).WillByDefault([this](){ return Real::dont_run(); });
     }
   
     void delegate(){
         ON_CALL(*this, run).WillByDefault([this](){
             return 1;
         });
         ON_CALL(*this, dont_run).WillByDefault([this](){
             return 2;
         });
     }
   };
   

2. 修改meson.build，消除符号冲突：
   编译测试程序时无需链接real.cpp，Mock类已继承Real的声明，调用基类实现可直接通过Real::method()完成：

   executable(
     'mock',
     files('mock.cpp'),
     dependencies: [dependency('gtest'), dependency('gmock')],
     install : false,
   )
   

3. 验证结果：
   修改后，测试用例中：

   • 调用delegate()前，mock.run()返回基类的0，mock.dont_run()返回基类的1
   • 调用delegate()后，run()返回1，dont_run()返回2
     所有断言将通过，GMOCK的"Uninteresting mock function call"警告也会消失。

内容的提问来源于stack exchange，提问作者CIsForCookies