caiy caiy - 2 months ago 28
C++ Question

Google Mock to test the real behaviors of a class

I am new to google test and google mock so I am still a little bit confused. I just tried to implement a simple calculator with integer addition, multiplication and division and create a mock for it which follows real behaviours. How can I fix it or where I did wrong?

Also can you explain to me how can I be sure that it is mocking the original class instead of directly calling the original class? Thank you ahead.

Here is CBasicMath.hpp:

#ifndef BASIC_MATH_HPP__
#define BASIC_MATH_HPP__

class CBasicMath
{
public:
CBasicMath(){}
virtual ~CBasicMath() {}
virtual int Addition(int x, int y);
virtual int Multiply(int x, int y);
virtual int Divide(int x, int y);
};

#endif //BASIC_MATH_HPP__


Here is CBasicMath.cpp:

#include "CBasicMath.hpp"

int CBasicMath::Addition(int x, int y)
{
return (x + y);
}

int CBasicMath::Multiply(int x, int y)
{
return (x * y);
}

int CBasicMath::Divide(int x, int y)
{
return (x / y);
}


Here is mock_basic_test.cpp:

#include "gmock/gmock.h"
#include "CBasicMath.cpp"

using ::testing::_;
using ::testing::AtLeast;
using ::testing::Invoke;

class MockBasicTest : public CBasicMath {
public:
MockBasicTest() {
// By default, all calls are delegated to the real object.
ON_CALL(*this, Addition(_))
.WillByDefault(Invoke(&real_, &CBasicMath::Addition));
ON_CALL(*this, Multiply(_))
.WillByDefault(Invoke(&real_, &CBasicMath::Multiply));
ON_CALL(*this, Divide(_))
.WillByDefault(Invoke(&real_, &CBasicMath::Divide));
}
MOCK_METHOD2(Addition, int(int x, int y));
MOCK_METHOD2(Multiply, int(int x, int y));
MOCK_METHOD2(Divide, int(int x, int y));
private:
CBasicMath real_;
};


Here is TestBasicMath:

#include "mock_basic_test.h"
#include "gtest/gtest.h"
#include "gmock/gmock.h"

class BasicMathTest : public ::testing::Test {
protected:
BasicMathTest() {}

virtual ~BasicMathTest() {}

virtual void SetUp() {
mTestObj = new CBasicMath();
}

virtual void TearDown() {
delete mTestObj;
}
CBasicMath *mTestObj;
};

TEST_F(BasicMathTest, testAddition) {
MockBasicTest basictest;
EXPECT_CALL(basictest, Addition(2,3))
.Times(1);
EXPECT_EQ(5,basictest.Addition(2,3));
}

TEST_F(BasicMathTest, testMultiply) {
EXPECT_EQ(6,mTestObj->Multiply(2,3));
}

TEST_F(BasicMathTest, testDivide) {
EXPECT_EQ(6,mTestObj->Divide(6,1));
}

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


It gives me errors like the following for all three functions:

In file included from /home/gmock-1.7.0/include/gmock/gmock-generated-function-mockers.h:43:0,
from /home/gmock-1.7.0/include/gmock/gmock.h:61,
from mock_basic_test.h:1,
from TestBasicMath_GoogleTest.cpp:1:
mock_basic_test.h: In constructor ‘MockBasicTest::MockBasicTest()’:
mock_basic_test.h:12:30: error: no matching function for call to ‘MockBasicTest::gmock_Addition(const testing::internal::AnythingMatcher&)’
ON_CALL(*this, Addition(_))
^
mock_basic_test.h:12:30: note: candidate is:
In file included from /home/gmock-1.7.0/include/gmock/gmock.h:61:0,
from mock_basic_test.h:1,
from TestBasicMath_GoogleTest.cpp:1:
mock_basic_test.h:19:2: note: testing::internal::MockSpec<int(int, int)>&MockBasicTest::gmock_Addition(const testing::Matcher<int>&, const testing::Matcher<int>&)
MOCK_METHOD2(Addition, int(int x, int y));
^
mock_basic_test.h:19:2: note: candidate expects 2 arguments, 1 provided


Thank you again for any help.

Answer

In your mocking class constructor code

ON_CALL(*this, Addition(_))
    .WillByDefault(Invoke(&real_, &CBasicMath::Addition));

the number of matchers (_) need to be the same as the number of parameters defined for the function signature:

ON_CALL(*this, Addition(_,_))
                    //   ^^  Add an additional matcher
    .WillByDefault(Invoke(&real_, &CBasicMath::Addition));

// ...

MOCK_METHOD2(Addition, int(int x, int y));
                        // ^^^^^  ^^^^^ here you have 2 parameters need matching
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