Mock NSHTTPURLRequest and NSHTTPURLResponse in iOS unit test

I'm developing a framework in iOS which makes HTTP calls to server.I wanted to write unit test to test the API's.I wanted to mock the server calls,without actually making real server call.Can anyone help me with sample unit test which makes mocked server calls.How to do we set expectations and return the hand constructed url response.?I'm using XCTest framework for unit test and OCMock for mocking objects.