Can googlemock C function?

[yun....@gmail.com]

Hello,

Is it possible to mock C style function using googlemock?

regards,
Xu

[Chris Henry]

On Sat, Dec 27, 2008 at 6:39 AM, <yun....@gmail.com> wrote:
>
> Hello,
>
> Is it possible to mock C style function using googlemock?

I don't have experience with this. But here is my take.

Let's talk about the mocking of C functions in general. There are two cases:

1) Calling C function similar to static method:
void doSomething() {
call_this_c_func();
}
in this case call_this_c_func is hard to mock. It is similar to static
methods and is a global name. (If call_this_c_func is in another
library, you can probably dynamically linked a mock library instead of
the real one.)

2) Mocking C function used as function pointer:
void doSomething(void (*func)()) {
func();
}
In this case, it's reasonably easy to mock *func (this is actually
very similar to dependency injection in C++). You can even do this
with C++, just write a mock class with a mock method. Write a function
with similar signature as *func and call the mock method in the mock
class. Pass this function to the function under test (after setting
expectations on the mock method).

That's my take. HTH,

--
Chris
chrish...@gmail.com
+65 9755 3292 (2 more weeks to Singapore!)

[Zhanyong Wan (λx.x x)]

What Chris says would work. My favorite solution is this:

Instead of calling a free function (say, OpenFile) directly, introduce
an abstract class (interface) for it and have a concrete subclass that
calls the free functio:

class FileInterface ｛
public:
...
virtual bool Open(const char* path, const char* mode) = 0;
};

class File : public FileInterface {
public:
...
virtual bool Open(const char* path, const char* mode) {
return OpenFile(path, mode);
}
};

Your code should talk to FileInterface to open a file. Now it's easy
to mock out the function.

This may seem much hassle, but in practice you often have multiple
related functions that you can put in the interface, so the
per-function overhead can be much lower.

--
Zhanyong

[Zhanyong Wan (λx.x x)]

This technique also works:

http://code.google.com/p/googlemock/wiki/CookBook#Mocking_Non-virtual_Methods

--
Zhanyong

[yun....@gmail.com]

Thanks you Chris.

On Dec 28 2008, 4:51 am, "Chris Henry" <chrishenry...@gmail.com>
wrote:

> chrishenry...@gmail.com

[yun....@gmail.com]

Thank you Zhanyong,

On Dec 30 2008, 2:14 am, Zhanyong Wan (λx.x x) <w...@google.com>
wrote:
> This technique also works:
>
> http://code.google.com/p/googlemock/wiki/CookBook#Mocking_Non-virtual...

>
> On Mon, Dec 29, 2008 at 10:09 AM, Zhanyong Wan (λx.x x) <w...@google.com> wrote:
>
>
>
> > What Chris says would work. My favorite solution is this:
>
> > Instead of calling a free function (say, OpenFile) directly, introduce
> > an abstract class (interface) for it and have a concrete subclass that
> > calls the free functio:
>
> > class FileInterface ｛
> > public:
> > ...
> > virtual bool Open(const char* path, const char* mode) = 0;
> > };
>
> > class File : public FileInterface {
> > public:
> > ...
> > virtual bool Open(const char* path, const char* mode) {
> > return OpenFile(path, mode);
> > }
> > };
>
> > Your code should talk to FileInterface to open a file. Now it's easy
> > to mock out the function.
>
> > This may seem much hassle, but in practice you often have multiple
> > related functions that you can put in the interface, so the
> > per-function overhead can be much lower.
>

> > On Sat, Dec 27, 2008 at 12:51 PM, Chris Henry <chrishenry...@gmail.com> wrote:

>
> >> On Sat, Dec 27, 2008 at 6:39 AM, <yun.y...@gmail.com> wrote:
>
> >>> Hello,
>
> >>> Is it possible to mock C style function using googlemock?
>
> >> I don't have experience with this. But here is my take.
>
> >> Let's talk about the mocking of C functions in general. There are two cases:
>
> >> 1) Calling C function similar to static method:
> >> void doSomething() {
> >> call_this_c_func();
> >> }
> >> in this case call_this_c_func is hard to mock. It is similar to static
> >> methods and is a global name. (If call_this_c_func is in another
> >> library, you can probably dynamically linked a mock library instead of
> >> the real one.)
>
> >> 2) Mocking C function used as function pointer:
> >> void doSomething(void (*func)()) {
> >> func();
> >> }
> >> In this case, it's reasonably easy to mock *func (this is actually
> >> very similar to dependency injection in C++). You can even do this
> >> with C++, just write a mock class with a mock method. Write a function
> >> with similar signature as *func and call the mock method in the mock
> >> class. Pass this function to the function under test (after setting
> >> expectations on the mock method).
>
> >> That's my take. HTH,
>
> >> --
> >> Chris

> >> chrishenry...@gmail.com