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"""Tools for creating tests of implementations of the Face layer."""

import abc

import six

# face_interfaces and interfaces are referenced in specification in this module.
from grpc.framework.face import interfaces as face_interfaces  # pylint: disable=unused-import
from tests.unit.framework.face.testing import interfaces  # pylint: disable=unused-import


class FaceTestCase(six.with_metaclass(abc.ABCMeta)):
  """Describes a test of the Face Layer of RPC Framework.

  Concrete subclasses must also inherit from unittest.TestCase and from at least
  one class that defines test methods.
  """

  @abc.abstractmethod
  def set_up_implementation(
      self, name, methods, method_implementations,
      multi_method_implementation):
    """Instantiates the Face Layer implementation under test.

    Args:
      name: The service name to be used in the test.
      methods: A sequence of interfaces.Method objects describing the RPC
        methods that will be called during the test.
      method_implementations: A dictionary from string RPC method name to
        face_interfaces.MethodImplementation object specifying
        implementation of an RPC method.
      multi_method_implementation: An face_interfaces.MultiMethodImplementation
        or None.

    Returns:
      A sequence of length two the first element of which is a
        face_interfaces.GenericStub (backed by the given method
        implementations), and the second element of which is an arbitrary memo
        object to be kept and passed to tearDownImplementation at the conclusion
        of the test.
    """
    raise NotImplementedError()

  @abc.abstractmethod
  def tear_down_implementation(self, memo):
    """Destroys the Face layer implementation under test.

    Args:
      memo: The object from the second position of the return value of
        set_up_implementation.
    """
    raise NotImplementedError()