implemented command pattern.
This commit is contained in:
tylerlaberge
94
pypatterns/behavioral/command.py
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94
pypatterns/behavioral/command.py
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from abc import ABCMeta, abstractmethod
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class InvalidActionException(Exception):
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"""
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Exception for when an invalid action is called on a Receiver.
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"""
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pass
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class InvalidInvokerCommandException(Exception):
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"""
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Exception for when an invalid command is given to an Invoker to execute.
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"""
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class Receiver(object, metaclass=ABCMeta):
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"""
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Abstract receiver class as part of the Command pattern.
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"""
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def action(self, name, *args, **kwargs):
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"""
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Delegates which method to be called for a desired action.
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@param name: The name of the action to execute.
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@type name: str
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@param args: Any arguments for the action.
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@param kwargs: Any keyword arguments for the action.
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"""
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try:
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return getattr(self, name)(*args, **kwargs)
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except AttributeError:
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raise InvalidActionException
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class Command(object, metaclass=ABCMeta):
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"""
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Abstract Command class as part of the Command pattern.
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"""
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def __init__(self, receiver):
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"""
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Initialize a new command instance.
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@param receiver: The receiver for this command to use.
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@type receiver: Receiver
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"""
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self._receiver = receiver
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@abstractmethod
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def execute(self):
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"""
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Abstract method for executing an action.
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"""
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pass
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@abstractmethod
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def unexecute(self):
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"""
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Abstract method for unexecuting an action.
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"""
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pass
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class Invoker(object, metaclass=ABCMeta):
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"""
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Abstract Invoker class as part of the Command pattern.
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"""
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def __init__(self, valid_commands):
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"""
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Initialize a new Invoker instance.
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@param valid_commands: A list of command classes this invoker can handle.
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"""
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self._history = []
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self._valid_commands = valid_commands
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def execute(self, command):
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"""
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Execute a command.
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@param command: A command for the invoker to execute.
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@type command: Command
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"""
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if command.__class__ not in self._valid_commands:
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raise InvalidInvokerCommandException
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else:
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self._history.append(command)
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return command.execute()
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def undo(self):
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"""
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Undo the last command.
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"""
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return self._history.pop().unexecute()
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190
tests/behavioral_tests/test_command.py
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190
tests/behavioral_tests/test_command.py
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from unittest import TestCase
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from pypatterns.behavioral.command import InvalidActionException, InvalidInvokerCommandException, \
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Receiver, Command, Invoker
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class ReceiverTestCase(TestCase):
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"""
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Unit testing class for the Receiver class.
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"""
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def setUp(self):
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"""
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Initialize testing data.
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"""
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class Thermostat(Receiver):
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def raise_temp(self, amount):
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return "Temperature raised by {0} degrees".format(amount)
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def lower_temp(self, amount):
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return "Temperature lowered by {0} degrees".format(amount)
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self.thermostat = Thermostat()
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def test_valid_action(self):
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"""
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Test the action method with a valid action.
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@raise AssertionError: If the test fails.
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"""
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self.assertEquals("Temperature raised by 5 degrees", self.thermostat.action('raise_temp', 5))
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self.assertEquals("Temperature lowered by 5 degrees", self.thermostat.action('lower_temp', 5))
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def test_invalid_action(self):
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"""
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Test the action method with an invalid action.
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@raise AssertionError: If the test fails.
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"""
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with self.assertRaises(InvalidActionException):
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self.thermostat.action('foo')
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class CommandTestCase(TestCase):
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"""
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Unit testing class for the Command class.
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"""
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def setUp(self):
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"""
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Initialize testing data.
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"""
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class Thermostat(Receiver):
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def raise_temp(self, amount):
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return "Temperature raised by {0} degrees".format(amount)
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def lower_temp(self, amount):
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return "Temperature lowered by {0} degrees".format(amount)
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class RaiseTempCommand(Command):
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def __init__(self, receiver, amount=5):
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super().__init__(receiver)
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self.amount = amount
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def execute(self):
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return self._receiver.action('raise_temp', self.amount)
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def unexecute(self):
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return self._receiver.action('lower_temp', self.amount)
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class LowerTempCommand(Command):
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def __init__(self, receiver, amount=5):
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super().__init__(receiver)
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self.amount = amount
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def execute(self):
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return self._receiver.action('lower_temp', self.amount)
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def unexecute(self):
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return self._receiver.action('raise_temp', self.amount)
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self.thermostat = Thermostat()
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self.raise_temp_command_class = RaiseTempCommand
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self.lower_temp_command_class = LowerTempCommand
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def test_execute(self):
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"""
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Test the execute method.
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@raise AssertionError: If the test fails.
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"""
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raise_temp_command = self.raise_temp_command_class(self.thermostat, 10)
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lower_temp_command = self.lower_temp_command_class(self.thermostat, 5)
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self.assertEquals("Temperature raised by 10 degrees", raise_temp_command.execute())
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self.assertEquals("Temperature lowered by 5 degrees", lower_temp_command.execute())
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class InvokerTestCase(TestCase):
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"""
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Unit testing class for the Invoker class.
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"""
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def setUp(self):
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"""
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Initialize testing data.
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"""
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class Thermostat(Receiver):
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def raise_temp(self, amount):
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return "Temperature raised by {0} degrees".format(amount)
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def lower_temp(self, amount):
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return "Temperature lowered by {0} degrees".format(amount)
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class RaiseTempCommand(Command):
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def __init__(self, receiver, amount=5):
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super().__init__(receiver)
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self.amount = amount
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def execute(self):
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return self._receiver.action('raise_temp', self.amount)
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def unexecute(self):
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return self._receiver.action('lower_temp', self.amount)
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class LowerTempCommand(Command):
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def __init__(self, receiver, amount=5):
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super().__init__(receiver)
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self.amount = amount
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def execute(self):
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return self._receiver.action('lower_temp', self.amount)
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def unexecute(self):
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return self._receiver.action('raise_temp', self.amount)
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class Worker(Invoker):
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def __init__(self):
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super().__init__([LowerTempCommand, RaiseTempCommand])
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self.worker = Worker()
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self.receiver = Thermostat()
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self.lower_temp_command = LowerTempCommand(self.receiver)
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self.raise_temp_command = RaiseTempCommand(self.receiver)
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def test_valid_execute(self):
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"""
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Test the execute method with a valid command for the Worker Invoker.
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@raise AssertionError: If the test fails.
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"""
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self.assertEquals("Temperature lowered by 5 degrees", self.worker.execute(self.lower_temp_command))
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self.assertEquals("Temperature raised by 5 degrees", self.worker.execute(self.raise_temp_command))
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def test_invalid_execute(self):
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"""
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Test the execute method with an invalid command for the Worker Invoker.
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@raise AssertionError: If the test fails.
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"""
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class Light(Receiver):
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def turn_on(self):
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return "Light turned on"
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def turn_off(self):
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return "Light turned off"
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class TurnOnLightCommand(Command):
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def execute(self):
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return self._receiver.action('turn_on')
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def unexecute(self):
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return self._receiver.action('turn_off')
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with self.assertRaises(InvalidInvokerCommandException):
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self.worker.execute(TurnOnLightCommand(Light))
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def test_undo(self):
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"""
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Test the undo method.
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@raise AssertionError: If the test fails.
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"""
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self.worker.execute(self.raise_temp_command)
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self.assertIn(self.raise_temp_command, self.worker._history)
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self.assertEquals("Temperature lowered by 5 degrees", self.worker.undo())
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self.assertNotIn(self.raise_temp_command, self.worker._history)
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