Writing tests for the new strategy
==================================

To write tests you either need to create a file called :code:`test_<library>.py`
where :code:`<library>.py` is the name of the file you have created or similarly
add tests to the test file that is already present in the
:code:`axelrod/tests/strategies/` directory.

Typically we want to test the following:

* That the strategy behaves as intended on the first move and subsequent
  moves, triggering any expected actions
* That the strategy initializes correctly

A :code:`TestPlayer` class has been written that has
a member function :code:`versus_test` which can be used to test how the player
plays against a given opponent.
It takes an optional keyword
argument :code:`seed` (useful and necessary for stochastic strategies,
:code:`None` by default)::

    self.versus_test(opponent=axelrod.MockPlayer(actions=[C, D]),
                     expected_actions=[(D, C), (C, D), (C, C)], seed=None)

In this case the player is tested against an opponent that will cycle through
:code:`C, D`. The :code:`expected_actions` are the actions played by both
the tested player and the opponent in the match. In this case we see that the
player is expected to play :code:`D, C, C` against :code:`C, D, C`.

Note that you can either user a :code:`MockPlayer` that will cycle through a
given sequence or you can use another strategy from the Axelrod library.

The function :code:`versus_test` also accepts a dictionary parameter of
attributes to check at the end of the match. For example this test checks
if the player's internal variable :code:`opponent_class` is set to
:code:`"Cooperative"`::

    actions = [(C, C)] * 6
    self.versus_test(axelrod.Cooperator(), expected_actions=actions
                     attrs={"opponent_class": "Cooperative"})

Note here that instead of passing a sequence of actions as an opponent we are
passing an actual player from the axelrod library.

The function :code:`versus_test` also accepts a dictionary parameter of match
attributes that dictate the knowledge of the players. For example this test
assumes that players do not know the length of the match::

     actions = [(C, C), (C, D), (D, C), (C, D)]
     self.versus_test(axelrod.Alternator(), expected_actions=actions,
                      match_attributes={"length": float("inf")})

The function :code:`versus_test` also accepts a dictionary parameter of
keyword arguments that dictate how the player is initiated. For example this
tests how the player plays when initialised with :code:`p=1`::

     actions = [(C, C), (C, D), (C, C), (C, D)]
     self.versus_test(axelrod.Alternator(), expected_actions=actions,
                      init_kwargs={"p": 1})

As an example, the tests for Tit-For-Tat are as follows::

    import axelrod
    from test_player import TestPlayer

    C, D = axelrod.Action.C, axelrod.Action.D

    class TestTitForTat(TestPlayer):
        """
        Note that this test is referred to in the documentation as an example on
        writing tests.  If you modify the tests here please also modify the
        documentation.
        """

        name = "Tit For Tat"
        player = axelrod.TitForTat
        expected_classifier = {
            'memory_depth': 1,
            'stochastic': False,
            'makes_use_of': set(),
            'inspects_source': False,
            'manipulates_source': False,
            'manipulates_state': False
        }

        def test_strategy(self):
            self.first_play_test(C)
            self.second_play_test(rCC=C, rCD=D, rDC=C, rDD=D)

            # Play against opponents
            actions = [(C, C), (C, D), (D, C), (C, D)]
            self.versus_test(axelrod.Alternator(), expected_actions=actions)

            actions = [(C, C), (C, C), (C, C), (C, C)]
            self.versus_test(axelrod.Cooperator(), expected_actions=actions)

            actions = [(C, D), (D, D), (D, D), (D, D)]
            self.versus_test(axelrod.Defector(), expected_actions=actions)

            # This behaviour is independent of knowledge of the Match length
            actions = [(C, C), (C, D), (D, C), (C, D)]
            self.versus_test(axelrod.Alternator(), expected_actions=actions,
                             match_attributes={"length": float("inf")})

            # We can also test against random strategies
            actions = [(C, D), (D, D), (D, C), (C, C)]
            self.versus_test(axelrod.Random(), expected_actions=actions,
                             seed=0)

            actions = [(C, C), (C, D), (D, D), (D, C)]
            self.versus_test(axelrod.Random(), expected_actions=actions,
                             seed=1)

            #  If you would like to test against a sequence of moves you should use
            #  a MockPlayer
            opponent = axelrod.MockPlayer(actions=[C, D])
            actions = [(C, C), (C, D), (D, C), (C, D)]
            self.versus_test(opponent, expected_actions=actions)

            opponent = axelrod.MockPlayer(actions=[C, C, D, D, C, D])
            actions = [(C, C), (C, C), (C, D), (D, D), (D, C), (C, D)]
            self.versus_test(opponent, expected_actions=actions)


There are other examples of using this testing framework in
:code:`axelrod/tests/strategies/test_titfortat.py`.

The :code:`expected_classifier` dictionary tests that the classification of the
strategy is as expected (the tests for this is inherited in the :code:`init`
method). Please be sure to classify new strategies according to the already
present dimensions but if you create a new dimension you do not **need** to re
classify all the other strategies (but feel free to! :)), but please do add it
to the :code:`default_classifier` in the :code:`axelrod/player.py` parent class.