I am new to gmock, so I want to know how can I stub simple C function called in a function under test for Unit Testing.
Example:
int func(int a)
{
boolean find;
// Some code
find = func_1();
return find;
}
I have searched about gmock and in my understanding gmock does not provide functionality to stub simple C functions, therefore I want to ask does gmock provides functionality to mock or stub func_1
?
If not how can I stub func_1
manually in my test code without changing source code? I am using google test framework for unit testing.
Thanks.
I found myself in the same situation lately. I had to write unit tests for libraries written in C, which in turn had dependencies to other libraries also written in C. So I wanted to mock all function calls of dependencies using gmock. Let me explain my approach by an example.
Assume the code to be tested (library A) calls a function from another library, lib_x_function()
:
lib_a_function()
{
...
retval = lib_x_function();
...
}
So, I want to mock the library X. Therefore I write an interface class and a
mock class in a file lib_x_mock.h
:
class LibXInterface {
public:
virtual ~LibXInterface() {}
virtual int lib_x_function() = 0;
}
class LibXMock : public LibXInterface {
public:
virtual ~LibXMock() {}
MOCK_METHOD0(lib_x_function, int());
}
Additionally I create a source file (say, lib_x_mock.cc
), that defines a stub
for the actual C function. This shall call the mock method. Note the extern
reference to the mock object.
#include lib_x.h
#include lib_x_mock.h
extern LibXMock LibXMockObj; /* This is just a declaration! The actual
mock obj must be defined globally in your
test file. */
int lib_x_function()
{
return LibXMockObj.lib_x_function();
}
Now, in the test file, which tests the library A, I must define the mock object
globally, so that it is both reachable within your tests and from
lib_x_mock.cc
. This is lib_a_tests.cc:
#include lib_x_mock.h
LibXMock LibXMockObj; /* This is now the actual definition of the mock obj */
...
TEST_F(foo, bar)
{
EXPECT_CALL(LibXMockObj, lib_x_function());
...
}
This approach works perfectly for me, and I have dozens of tests and several mocked libraries. However, I have a few doubts if it is ok to create a global mock object - I asked this in a separate question and still wait for answers. Besides this I'm happy with the solution.
EDIT: The problem about the global object can be easily remedied by creating the object e.g. in the constructor of the test fixture, and just storing a pointer to that object in a global variable.
However, also note my alternative answer to this question, that I just posted.