Mocking methods that return scoped_ptr

[Marshall Greenblatt]

Hi All,

I'm adding a new interface that returns values using scoped_ptr like this:

virtual scoped_ptr<gfx::Image> GetImageNamed(int resource_id) = 0;

I would like to mock out the new interface for testing purposes but I'm not sure how to handle these methods. For example, the following does not work because scoped_ptr has no copy constructor:

MOCK_METHOD1(GetImageNamed, scoped_ptr<gfx::Image>(int resource_id));

What is the correct way to mock these methods? Is there an existing mock implementation somewhere in the code that I could use as a model?

Thanks,
Marshall

[Marshall Greenblatt]

The problem using Gmock with scoped_ptr has been discussed previously:
http://groups.google.com/a/chromium.org/group/chromium-dev/msg/ddd7942f93b8ed4b

Was a good solution ever discovered?
 

Thanks,
Marshall

[Sergey Ulanov]

You can use the following hack for such methods:

class MockObject {

 public:

  MOCK_METHOD0(ReturnsScopedPtrMock, Type*());

  virtual scoped_ptr<Type> ReturnsScopedPtr() OVERRIDE {

    return scoped_ptr<Type>(ReturnsScopedPtrMock());

  }

};

Then you set expectations for ReturnsScopedPtrMock() instead of ReturnsScopedPtr(). You can also apply similar hack to mock methods that accept scoped_ptr<> parameters (for example see MockVideoStub in remoting/protocol/protocol_mock_objects.h). I don't think there is a better solution right now.

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[Alexei Svitkine]

On Tue, May 1, 2012 at 5:06 PM, Sergey Ulanov <ser...@chromium.org> wrote:
>   MOCK_METHOD0(ReturnsScopedPtrMock, Type*());
>   virtual scoped_ptr<Type> ReturnsScopedPtr() OVERRIDE {
>     return scoped_ptr<Type>(ReturnsScopedPtrMock());
>   }

Sounds like it should be possible to make a new MOCK_SCOPED_PTR_* macro
that would do that...

-Alexei

[Marshall Greenblatt]

On Tue, May 1, 2012 at 5:06 PM, Sergey Ulanov <ser...@chromium.org> wrote:

You can use the following hack for such methods:

class MockObject {

 public:

  MOCK_METHOD0(ReturnsScopedPtrMock, Type*());

  virtual scoped_ptr<Type> ReturnsScopedPtr() OVERRIDE {

    return scoped_ptr<Type>(ReturnsScopedPtrMock());

  }

};

Then you set expectations for ReturnsScopedPtrMock() instead of ReturnsScopedPtr(). You can also apply similar hack to mock methods that accept scoped_ptr<> parameters (for example see MockVideoStub in remoting/protocol/protocol_mock_objects.h). I don't think there is a better solution right now.

Thanks, that works :-).
 

[Drew Wilson]

Reading through that other thread - did we ever start moving forward on migrating existing (or just new?) APIs to using scoped_ptr::Pass() instead of raw pointers? Or does Gmock provide enough friction that we're never really going to make widespread use of it?

-atw

[Ami Fischman]

Reading through that other thread - did we ever start moving forward on migrating existing (or just new?) APIs to using scoped_ptr::Pass() instead of raw pointers? Or does Gmock provide enough friction that we're never really going to make widespread use of it?

I haven't heard of the gmock-related friction stopping anyone.  codesearch says there are lots of uses of the new API.

Anecdote: I converted media/-related code and it was quite satisfying to replace comments like "takes ownership of |foo|" with the compiler-checked annotation of scoped_ptr/Pass().

Cheers,

-a

[Wez]

+1... we've been migrating Chromoting to use Pass() and so far it's
been a relatively painless win for us. :)