GMock passing a mocked object into another, and calling a stubed method is still calling real logic

问题

I'm trying to pass a mocked object to another object's method and call it, i get the same result as I would call real method.

fooa.h - this is the real class

#ifndef FOOA_H
#define FOOA_H
class FooA
{
public:
 FooA();
 virtual int method(int a, int b, int c, int d);
};

#endif // FOOA_H

fooa.cpp

#include "fooa.h"

FooA::FooA()
{

}

int FooA::method(int a, int b, int c, int d)
{
    return a+b+c+d;
}

mockedfooa.h - mocked version of fooa

#ifndef MOCKEDFOOA_H
#define MOCKEDFOOA_H
#include "fooa.h"
#include <gmock/gmock.h>


class MockedFooA : public FooA
{
public:
    MOCK_METHOD4( method, int(int a, int b, int c, int d) );
};
#endif // MOCKEDFOOA_H

calculator.h this class invokes method from FooA class

#include "fooa.h"
#include <iostream>
class Calculator
{
public:
    Calculator()
    { }
    void doCalc(FooA foo)
    {
        int a = 3, b =4 ,c = 12, d = 41;
        std::cout<<foo.method(a,b,c,d)<<std::endl;
    }
};

And my main function

#include "MockedFooA.h"
#include "calc.h"

using ::testing::_;
using ::testing::Return;

using namespace std;
int main(int argc, char *argv[])
{

    Calculator oCalc; // object that uses the oFoo.method

    FooA oFoo;//not mocked
    oCalc.doCalc(oFoo);

    MockedFooA oMockedFoo ; // mocked
    ON_CALL(oMockedFoo,method(_,_,_,_)).WillByDefault(Return(20));
    oCalc.doCalc(oMockedFoo);

}

The output is

60
60

so it looks like even though it is stubbed doCalc still invokes the real method.

And my question is: Why when i'm passing mocked object to doCalc method isn't calling stubbed method?

回答1:

The problem is that you're passing the mocked object by value. Since mock objects exploit the dynamic binding provided by inheritance, you need to pass them around using references or pointers. Otherwise you'll end up slicing your objects.

To achieve the desired behavior, change your doCalc method to take the FooA parameter by-reference instead of by-value. Like this:

void doCalc(FooA& foo)

来源：https://stackoverflow.com/questions/23063013/gmock-passing-a-mocked-object-into-another-and-calling-a-stubed-method-is-still

标签

c++

unit-testing

gmock