Using Google Mock with boost::bind

Question

I have a class whose constructor takes a Boost function, and I'd like to test it with Google Mock. The following code shows a sample class and my attempt to test it:

MyClass.h:

#include <boost/function.hpp>
class MyClass
{
public:
    MyClass(boost::function<void()> callback);
    void callCallback();
private:
    boost::function<void()> m_callback;
};

MyClassTest.cpp:

#include <gtest/gtest.h>
#include <gmock/gmock.h>
#include <boost/bind.hpp>
#include "MyClass.h"
class CallbackMock
{
public:
    MOCK_METHOD0(callback, void());
};

TEST(MyClassShould, CallItsCallback)
{
    CallbackMock callbackMock;
    MyClass myClass(boost::bind(&CallbackMock::callback, callbackMock));
    EXPECT_CALL(callbackMock, callback()).Times(1);
    myClass.callCallback();
}

Attempting to compile MyClassTest.cpp in Visual Studio 2008 gives the following error:

...gmock/gmock-generated-function-mockers.h(76) : error C2248: 'testing::internal::FunctionMockerBase::FunctionMockerBase' : cannot access private member declared in class 'testing::internal::FunctionMockerBase' 1> with 1> [ 1>
F=void (void) 1> ] 1>
.../gmock-spec-builders.h(1656) : see declaration of 'testing::internal::FunctionMockerBase::FunctionMockerBase' 1> with 1> [ 1>
F=void (void) 1> ] 1>
This diagnostic occurred in the compiler generated function 'testing::internal::FunctionMocker::FunctionMocker(const testing::internal::FunctionMocker &)' 1> with 1> [ 1>
Function=void (void) 1> ]

The error stems from the line containing boost::bind. Replacing the mocked method with void callback(){} eliminates the compile error (but also eliminates the use of Google Mock, defeating the purpose). Is what I'm trying to do possible without modifying the tested class?

Answer 1

The reason is that Google Mock mocks are not copyable - that is by design. When you try to pass it into boost::bind by value, the compiler fails to generate the copy constructor. You should take the mock's address when passing it into bind:

MyClass myClass(boost::bind(&CallbackMock::callback, &callbackMock));

Answer 2

I think this line is wrong:

MyClass myClass(boost::bind(&CallbackMock::callback, callbackMock));

The last parameter should be &callbackMock