How to GMOCK a function within function? - c++

Question

I have a function1 inside which function 2 is called. I have to mock only function2, whwenever i call function1 it should call real implementation of function1 and mock implementation of function2. Kindly help me on this
Display.cpp
#include "Display.h"
int DisIp::getip()
{
return 5;
}
int DisIp::display()
{
Addition obj;
int ip=obj.getip();
return ip;
}
Display.h
class DisIP
{
public:
int display();
int getip();
};
GMOCK file
#include <limits.h>
#include "gmock.h"
#include "gtest.h"
#include "Display.h"
#include <string>
using namespace std;
using ::testing::AtLeast;
using ::testing::_;
using ::testing::AnyNumber;
using ::testing::Gt;
using ::testing::Return;
using testing::ReturnPointee;
using ::testing::Invoke;
class MyInterface{
public:
virtual int display() = 0;
virtual int getip()=0;
};
class MockInter : public MyInterface
{
public:
MockInter()
{
ON_CALL(*this, getip()).WillByDefault(Invoke(&this, &MockInter::getip));
ON_CALL(*this, display()).WillByDefault(Invoke(&real, &Addition::display));
}
MOCK_METHOD0(display,int());
MOCK_METHOD0(getip,int());
DisIp real;
};
class DisplayTest : public ::testing::Test {
protected:
virtual void SetUp() {
}
virtual void TearDown() {
// Code here will be called immediately after each test
// (right before the destructor).
}
};
TEST_F(DisplayTest,ip){
MockInter mock;
//EXPECT_EQ(1,mock.display());
EXPECT_EQ(1,mock.getip());
}

Answer 1

Your design suffers from breaking Single Responsibility Principle.
Displaying and getting IP are two different responsibilities. It is even shown in your implementation of DisIp::display() - you get IP from so-called Addition obj. When you fix this design error - your unit tests becomes much easier and straightforward. But it is important to say that UT are only the symptom here, the bad design is a disease.
So how it could look like:
class IIpProvider
{
public:
virtual ~IIpProvider() = default;
virtual int getIp() = 0;
};
class DispIp
{
public:
DispIp(IIpProvider& ipProvider) : ipProvider(ipProvider) {}
int display()
{
int ip=ipProvider.getIp();
//...
return ip;
}
private:
IIpProvider& ipProvider;
};
then your Mock:
class IpProviderMock : public IIpProvider
{
public:
MOCK_METHOD0(getIp, int());
};
And your tests:
class DispIpTest : public ::testing::Test
{
protected:
IpProviderMock ipProviderMock;
DispIp objectUnderTest{ipProviderMock}; // object-under-test must be connected to object doubles (like mocks)
};
TEST_F(DispIpTest, shallUseProvidedIpToDisplay)
{
using namespace testing;
auto SOME_IP = 7;
EXPECT_CALL(ipProviderMock, getIp()).WillRepeatedly(Return(SOME_IP));
//...
ASSERT_EQ(SOME_IP, objectUnderTest.display());
}
In your original tests - main problem was also that your mock object was not connected in any way to your object under test.
If you do not like (cannot) to change your design (what I really advice) you have to use technique called partial mocking
In your case - it would something like this:
class DisIP
{
public:
int display();
virtual int getip(); // function for partial mocking must be virtual
};
class DisIPGetIpMock : public DisIP
{
public:
MOCK_METHOD0(getIp, int());
};
class DispIpTest : public ::testing::Test
{
protected:
DisIPGetIpMock objectUnderTest;
};
TEST_F(DispIpTest, shallUseProvidedIpToDisplay)
{
EXPECT_CALL(objectUnderTest, getIp()).WillRepeatedly(Return(SOME_IP));
...
ASSERT_EQ(SOME_IP, objectUnderTest.display());
}

Answer 2

You can use the Cutie library to mock C function GoogleMock style, if that will assist you.
There's a full sample in the repo, but just a taste:
INSTALL_MOCK(fclose);
CUTIE_EXPECT_CALL(fclose, _).WillOnce(Return(i));