CODEWITHSUNDEEP
ccmakecmocka
user2156513
user2156513

Reputation: 113

How to use cmocka library to mock a function from 3rd party library which cannot be modified?

I am trying to write a test case in c using cmocka library.My testcase is testing a function which then internally calls a function from a 3rd party library (cannot modify the library).This function return NULL value when application is not up and running,so i want to mock the return value for this 3rd party library function.How can i achieve this?

I have tried using will_return function of cmocka to get desired return value,but it does not work

void third_party_func()
{
   return mock();
}
void my_func_to_be_tested()
{
   int ret;
   ret = third_party_func();
   return ret;
}
void test_do_mytest(void ** state)
{
   (void) state;
   int ret;
   will_return(third_party_func,1);
   ret = my_func_to_be_tested();
   assert_int_equal(1,ret);
}
const struct CMUnitTest tests[] = {
    cmocka_unit_test(test_do_mytest),
};


int main(void)
{
    return cmocka_run_group_tests(tests, NULL, NULL);
}

I get compilation error that multiple definition for third_party_func().How to handle such case?

I want to get desired value as return value for my third party func.

Upvotes: 3

Views: 1651

Answers (1)

Oka
Oka

Reputation: 101

Have you tried the __wrap_ flag ?

Change the name of your function from third_party_func to __wrap_third_party_func and add the following directive to gcc , for example with fopen function : 

FILE * __wrap_fopen(const char *__restrict __filename,
                const char *__restrict __modes)
{
  return mock_ptr_type(FILE*);

}

and add the directive to gcc like : 

$ gcc -g -Wl,--wrap=fopen

Hope it'll help !

Upvotes: 2

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