One day, I was disapointed when I couldn't find what COM_VERIFY was in the example code of this XML tutorial.
After few researches, I found the definition here:

#include <atlbase.h>

#define ASSERT(x) ATLASSERT(x)

#if defined _DEBUG
#define COM_VERIFY(x) ASSERT(SUCCEEDED(x))
#else
#define COM_VERIFY(x) ((void)(x))
#endif