在 gtest 中模拟纯虚函数并使用 expect_call 进行测试

Question

I am trying to test a function call from another function using gtest. A simplified version of the header and cpp files are: Sample.h

class Sample {
public:
   Sample();
   ~Sample();
   void funcA();
protected:
   virtual void funcB()=0;
};

In Sample.cpp the funcA calls funcB.

funcA() {
   funcB();
}

The code works as expected but writing its unit test fails. The example of unit test I wrote is as following:

testSample.cpp

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

class SampleMock : public Sample {
public:
    SampleMock(): SampleMock(){};
    virtual ~SampleMock(){};
    MOCK_METHOD0(funcB, void());
};

class SampleTest : public ::testing::Test {
protected:
    void SetUp() override
    {
        sample = new SampleMock();
    }

    void TearDown() override
    {
        delete sample;
    }
    Sample* sample;
};

TEST_F(SampleTest, Test1)
{
    SampleMock tempObj;
    EXPECT_CALL(tempObj, funcB);
    sample->funcA();
}
}

I want to run a test and make sure that on the invocation of funcA, funcB is called. But running this test throws the error

Undefined symbols for architecture x86_64:
  "Sample::funcA()", referenced from:
      SampleTest_Test1_Test::TestBody() in testSample.o
  "Sample::Sample(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&)", referenced from:
      SampleMock::SampleMock() in testSample.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

What am I doing wrong here?

Answer 1

There are a few things wrong with the code example you show:

You are inheriting from Sample, so change this:

~Sample();

to:

virtual ~Sample() = default;

---

Also in the `SampleMock` class, the constructor is delegating to itself:

SampleMock(): Sample(){};

You probably meant to:

SampleMock* sample; // instead of Sample* sample

---

 SampleMock* sample; // instead of Sample* sample

Regarding your test, EXPECT_CALL expects a mock. I'm not entirely sure what the intent is in the test. Anyway, this should get you passed compilation:

Make funcA virtual: virtual void funcA()

Mocked class becomes like this

class SampleTest : public ::testing::Test {
public:
  // ...
  SampleMock* sample;
};

SampleTest :

TEST_F(SampleTest, Test1)
{
  EXPECT_CALL(*sample, funcA).WillOnce([this]() {
    sample->Sample::funcA();
  });

  EXPECT_CALL(*sample, funcB).Times(1);

  sample->funcA();
}

And the test will once called with funcA delegate it to the base, and we expect that funcB also be called.

 TEST_F(SampleTest, Test1) { EXPECT_CALL(*sample, funcA).WillOnce([this]() { sample->Sample::funcA(); }); EXPECT_CALL(*sample, funcB).Times(1); sample->funcA(); }