def add_expectation(self, caller):
        """Adds a new expectation for the method.

        :return: The new ``Expectation``.
        :rtype: Expectation
        """

        expectation = Expectation(self._target, self._method_name, caller)
        self._expectations.insert(0, expectation)
        return expectation
Adds a new expectation for the method.

        :return: The new ``Expectation``.
        :rtype: Expectation