Mock non-virtual method giving compilation error

Question

I need to write the gtest to test some existing code that has a non-virtual method, hence I am testing using the below source, but I am getting the compilation error

package/web/webscr/sample_template_class3.cpp: In function âint main()â: package/web/webscr/sample_template_class3.cpp:64: error: âclass Templatemyclassâ has no member named âgmock_displayâ

sample_template_class3.cpp

#include <iostream>
#include <gtest/gtest.h>
#include <gmock/gmock.h>

using namespace std;

template < class myclass>
class Templatemyclass
{
    private:
            myclass T;
    public :

        void display()
        {
            T.display();
        }

};

class Test
{
    public:
         void display()
        {
            cout<<"Inside the display Test:" <<endl;
        }

};

class MockTest

{
    public:
                MOCK_METHOD0(display,void());
};

class FinalTest
{
        public:
                        void show( Templatemyclass<Test> t)
                        {
                                t.display();
                                cout<<"Inside the display FinalTest:" <<endl;
                        }



};
int main()
{


FinalTest test1;
Templatemyclass<Test> obj1;
Templatemyclass<MockTest> obj2;
EXPECT_CALL(obj2,display()).Times(1);
test1.show(obj1);

return 1;
}

Answer 1

There are a couple of issues in your code. I have changed it below and commented the code by way of explanation. If this is not clear enough, add a comment and I'll try and explain further.

#include <iostream>
#include <gtest/gtest.h>
#include <gmock/gmock.h>

using namespace std;

template <class myclass>
class Templatemyclass {
 private:
  // Hold a non-const ref or pointer to 'myclass' so that the actual
  // object passed in the c'tor is used in 'display()'.  If a copy is
  // used instead, the mock expectations will not be met.
  myclass* T;
 public :
  // Pass 'myclass' in the c'tor by non-const ref or pointer.
  explicit Templatemyclass(myclass* t) : T(t) {}
  void display() { T->display(); }
};

class Test {
 public:
  void display() { cout << "Inside the display Test:" << endl; }
};

class MockTest {
 public:
  MOCK_METHOD0(display, void());
};

class FinalTest {
 public:
  // Templatise this function so we can pass either a Templatemyclass<Test>
  // or a Templatemyclass<MockTest>.  Pass using non-const ref or pointer
  // again so that the actual instance with the mock expectations set on it
  // will be used, and not a copy of that object.
  template<class T>
  void show(T& t) {
    t.display();
    cout<<"Inside the display FinalTest:" <<endl;
  }
};

int main() {
  Test test;
  Templatemyclass<Test> obj1(&test);

  MockTest mock_test;
  Templatemyclass<MockTest> obj2(&mock_test);
  EXPECT_CALL(mock_test,display()).Times(1);

  FinalTest test1;
  test1.show(obj1);
  test1.show(obj2);

  return 0;
}

The following could possibly simplify the case:

#include <iostream>
#include <gtest/gtest.h>
#include <gmock/gmock.h>

template <class myclass>
class Templatemyclass {
 public:
  myclass T;
  void show() const { T.display(); }
};

struct Test {
  void display() const { std::cout << "Inside the display Test:\n"; }
};

struct MockTest {
  MOCK_CONST_METHOD0(display, void());
};

int main() {
  Templatemyclass<Test> obj1;
  obj1.show();

  Templatemyclass<MockTest> obj2;
  EXPECT_CALL(obj2.T, display()).Times(1);
  obj2.show();

  return 0;
}

Answer 2

If you don't want to change your source code, you can leverage injector++. Currently it only supports x86 Windows. But Linux and x64 Windows support will come soon. Below examples will give you a brief idea:

Mock non-virtual methods

Below example fakes BaseClassTest::getAnInteger() by using fakeFunc():

class FakeClassNonVirtualMethodTestFixture : public ::testing::Test
{
public:
    int fakeFunc()
    {
        return 6;
    }
};

TEST_F(FakeClassNonVirtualMethodTestFixture, FakeIntFunctionWhenCalled)
{
    // Prepare
    int expected = 6;
    InjectorPP::Injector injector;

    injector.whenCalled(INJECTORPP_MEMBER_FUNCTION(BaseClassTest::getAnInteger))
        .willExecute(INJECTORPP_MEMBER_FUNCTION(FakeClassNonVirtualMethodTestFixture::fakeFunc));

    BaseClassTest b = BaseClassTest();

    // Act
    // FakeFunc will be executed!
    int actual = b.getAnInteger();

    // Assert
    EXPECT_EQ(expected, actual);
}

Mock virtual methods

Injector++ supports virtual method mocking (Amazing, huh?). Below is a simple example:

int FakeIntFuncForDerived()
{
    return 2;
}

TEST_F(FakeClassVirtualMethodTestFixture, MockDerivedClassVirtualMemberFunctionWhenCalled)
{
    // Prepare
    int expected = 2;
    BaseClassTest* derived = new SubClassTest();

    InjectorPP::Injector injector;
    injector.whenCalledVirtualMethod(derived, "getAnIntegerVirtual")
        .willExecute(fakeIntFuncForDerived);

    // Act
    // FakeIntFuncForDerived() will be exectued!
    int actual = derived->getAnIntegerVirtual();

    // Assert
    EXPECT_EQ(expected, actual);

    delete derived;
    derived = NULL;
}

Mock static methods

Injector++ supports static method mocking. Below is a simple example:

Address FakeGetAnAddress()
{
    Address addr;
    addr.setAddressLine("fakeAddressLine");
    addr.setZipCode("fakeZipCode");

    return addr;
}

TEST_F(FakeClassNonVirtualMethodTestFixture, FakeStaticFunctionReturnUserDefinedClassWhenCalled)
{
    // Prepare
    Address expected;
    expected.setAddressLine("fakeAddressLine");
    expected.setZipCode("fakeZipCode");

    InjectorPP::Injector injector;

    injector.whenCalled(INJECTORPP_STATIC_MEMBER_FUNCTION(BaseClassTest::getAnAddressStatic))
        .willExecute(INJECTORPP_MEMBER_FUNCTION(FakeClassNonVirtualMethodTestFixture::fakeGetAnAddress));

    // Act
    // FakeGetAnAddress will be executed!
    Address actual = BaseClassTest::getAnAddressStatic();

    // Assert
    EXPECT_EQ(expected, actual);
}