def wantFunction(self, function):
        """Is the function a test function?
        """
        try:
            if hasattr(function, 'compat_func_name'):
                funcname = function.compat_func_name
            else:
                funcname = function.__name__
        except AttributeError:
            # not a function
            return False
        declared = getattr(function, '__test__', None)
        if declared is not None:
            wanted = declared
        else:
            wanted = not funcname.startswith('_') and self.matches(funcname)
        plug_wants = self.plugins.wantFunction(function)
        if plug_wants is not None:
            wanted = plug_wants
        log.debug("wantFunction %s? %s", function, wanted)
        return wanted
Is the function a test function?