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I'm a beginner with google mock and I'm not sure how to use it and the concept.

If I'm trying to Test a method from a class that is calling some other methods from different classes. Do I need to mock all these methods from this different classes that my Test method is calling. Here is a example:

 class A { public: A () {} int setnum(int num) {//do some stuff return 1 or 0// } private: int _num; }; class B { public: B (){} int init(A *a, int number){ if(a->setnum(number)) return 1; return 0; } void setNum(int num){_num=num;} private: A *_a; int _num; }; class C { public: int doSoemthing(A *a, int number){ if (domore(a,number)) return 1; return 0; } int domore(A *a, int number){ if(_b.init(a,number)) return 1; return 0; ;} private: B _b; };

Do I need to mock all the methods from class A and B that I need to Test my Test method? Or can I just mock one Class , and test if this class is working.

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In order to test C class with mocks, you need to introduce an interface for the dependency than is to be used in C class (here, added BIface). Then you need to use dependency injection of BIface to C class (via added ctor). Having that you will be able to test interactions of B and C classes. IMO A class doesn't need to be mocked in CTest (but most probably need to be tested in BTest)

class A { public: A() {} // not needed int setnum(int num) { // do some stuff return 1 or 0// } private: int _num; }; class BIface { public: virtual ~BIface() = default; virtual int init(A *a, int number) = 0; virtual void setNum(int num) = 0; }; class B : public BIface { public: B() {} // not needed int init(A *a, int number) override { if (a->setnum(number)) return 1; return 0; } void setNum(int num) override { _num = num; } private: A *_a; int _num; }; class C { public: C(BIface &b) : _b{b} {} int doSoemthing(A *a, int number) { if (domore(a, number)) return 1; return 0; } int domore(A *a, int number) { if (_b.init(a, number)) return 1; return 0; ; } private: BIface &_b; }; class BIfaceMock : public BIface { public: MOCK_METHOD2(init, int(A *, int)); MOCK_METHOD1(setNum, void(int)); }; TEST(CTest, givenDoingMoreWhenInitOfBReturnOneThenReturnOne) { // can be done in CTest ctor if more tests are needed to avoid code duplciation BIfaceMock bMock{}; A a{}; // `a` doesn't need to be mocked in CTest. It shall be mocked in BTest as it is dependency of B class, not C class C testedObject{bMock}; // dependency injection of BFace to C const auto SOME_INT_PARAM = 42; // Eq mather is used to match both &a and SOME_INT_PARAM. This confirms proper parameters were passed to init EXPECT_CALL(bMock, init(&a, SOME_INT_PARAM)).WillOnce(Return(1)); ASSERT_EQ(1, testedObject.domore(&a, SOME_INT_PARAM)); }
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yes that is exactly how i started, but I was not sure if I need to mock class A,This is just a part of the code, it is a little bit complex I have singleton classes and I need to refactor the code to be able to test. But that's the answer I was searching for. Many Thanks
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I'm not 100% sure but in your example you don't have to use mocks at all. You can create your objects really easy here.

I would use mocks when I would expect that some method will be called and should return specific value - I'm not testing this method but for example if-statment:

 A a; if(a.method()) { // some logic }
  • To manipulate what if will get I would use mocks like this: EXPECT_CALL(aMock.method()).WillOnce(Return(true)); But you can use it in many more situations (e.g: you can avoid creating really big class and replace it with mock object).
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Sorry my mistake, I edit the code. This is just a simple example I have a much complicated code. So my question is do I need to mock A and B in this example
Even after code change you don't have to use mocks here. I see one situation if: int doMore(){ D d; if(d.isValid()){return 1;} return 0; } looks something like this (isValud() - return some value) -> if you want to in easy way control test-flow you can use mocks to accomplish it. Using mocks you can have two simple tests and test if your method return 1 and 0 with proper condition.
But what if doMore() depends from a method in class A
You can do it on this case but IMO with this kind od trivial classes you can create real objects(instead od nocka) in test case

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