c++ - 是否可以使用 gtest 或 gmock 模拟被调用函数的返回值？

Question

我是 gtest 和 gmock 的新手，请让我了解如何模拟被调用的函数。这也将帮助我提高代码覆盖率。

#include <stdio.h>
#include "gtest/gtest.h"

int ret()
{
    return 5;
}

class A
{
    public:
        A();
        int a;
        int func();
};

A::A()
{
    printf("This is constructor\n");
}

int A::func()
{
    int iRet = ret(); /* When func() is called by gtest I would like to control the return value of ret() */
    int iRet1 = ret();
    /* Based on these two values some operations to be done */
    printf("This is func. %d, %d\n", iRet, iRet1);
    return iRet;
}

TEST (abc, xyz) {
    A a;
    EXPECT_EQ(5, a.func()); /* Here how to get different values of iRet and iRet1 for ret() function? */
}

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

如果无法通过 gtest 和/或 gmock 实现，请向我推荐任何其他工具。

我还尝试了以下未按预期工作的东西:

int ret()
{
    printf("Returning 5\n");
    return 5;
}

int ret1()
{
    int iRet = 10;
    printf("Inside ret1\n");
    iRet = ret();
    if (iRet == 5)
    {
        printf("Original ret is called\n");
    }
    else if (iRet == 100)
    {
        printf("This is mocked function call\n");
    }
    else
    {
        printf("Opps! This should not happen\n");
    }
    return iRet;
}

class FooMock {
    public:
        MOCK_METHOD0(ret, int());
        MOCK_METHOD0(ret1, int());
};

TEST (abc, xyz) {
    FooMock mock;
    EXPECT_CALL(mock, ret()).Times(1).WillOnce(Return(100));
    mock.ret1();
}
int main(int argc, char **argv)
{
    ::testing::InitGoogleMock(&argc, argv);
    return RUN_ALL_TESTS();
}

运行时出现以下错误:

$ ./a.out 
[==========] Running 1 test from 1 test case.
[----------] Global test environment set-up.
[----------] 1 test from abc
[ RUN      ] abc.xyz
gtest.cpp:86: Failure
Actual function call count doesn't match EXPECT_CALL(mock, ret())...
         Expected: to be called once
           Actual: never called - unsatisfied and active
gtest.cpp:87: Failure
Actual function call count doesn't match EXPECT_CALL(mock, ret())...
         Expected: to be called once
           Actual: never called - unsatisfied and active
[  FAILED  ] abc.xyz (0 ms)
[----------] 1 test from abc (0 ms total)

[----------] Global test environment tear-down
[==========] 1 test from 1 test case ran. (0 ms total)
[  PASSED  ] 0 tests.
[  FAILED  ] 1 test, listed below:
[  FAILED  ] abc.xyz

 1 FAILED TEST

如果我做错了什么，请告诉我...

Answer 1

因此，单元测试的理念是运行一些代码，并将结果与​​预期结果进行比较。您的代码使它比必须的更复杂。例如

#include <stdio.h>
#include "gtest/gtest.h"

int incBy5(const int a) {
  return a+5;
}

TEST (abc, xyz) {
  int x=17;
  EXPECT_EQ(x+5, incBy5(x));
}

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

请参阅一般单元测试概念的文档，尤其是 google-test。这一切的模拟方面都随着更复杂的事情而出现，以测试您可能没有现成的一切(例如网络资源、数据库等)，并且您创建了可以替换这些资源的模型。