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from .._core import Automaton, NoTransition
from unittest import TestCase
class CoreTests(TestCase):
"""
Tests for Automat's (currently private, implementation detail) core.
"""
def test_NoTransition(self):
"""
A L{NoTransition} exception describes the state and input symbol
that caused it.
"""
# NoTransition requires two arguments
with self.assertRaises(TypeError):
NoTransition()
state = "current-state"
symbol = "transitionless-symbol"
noTransitionException = NoTransition(state=state, symbol=symbol)
self.assertIs(noTransitionException.symbol, symbol)
self.assertIn(state, str(noTransitionException))
self.assertIn(symbol, str(noTransitionException))
def test_noOutputForInput(self):
"""
L{Automaton.outputForInput} raises L{NoTransition} if no
transition for that input is defined.
"""
a = Automaton()
self.assertRaises(NoTransition, a.outputForInput,
"no-state", "no-symbol")
def test_oneTransition(self):
"""
L{Automaton.addTransition} adds its input symbol to
L{Automaton.inputAlphabet}, all its outputs to
L{Automaton.outputAlphabet}, and causes L{Automaton.outputForInput} to
start returning the new state and output symbols.
"""
a = Automaton()
a.addTransition("beginning", "begin", "ending", ["end"])
self.assertEqual(a.inputAlphabet(), {"begin"})
self.assertEqual(a.outputAlphabet(), {"end"})
self.assertEqual(a.outputForInput("beginning", "begin"),
("ending", ["end"]))
self.assertEqual(a.states(), {"beginning", "ending"})
def test_oneTransition_nonIterableOutputs(self):
"""
L{Automaton.addTransition} raises a TypeError when given outputs
that aren't iterable and doesn't add any transitions.
"""
a = Automaton()
nonIterableOutputs = 1
self.assertRaises(
TypeError,
a.addTransition,
"fromState", "viaSymbol", "toState", nonIterableOutputs)
self.assertFalse(a.inputAlphabet())
self.assertFalse(a.outputAlphabet())
self.assertFalse(a.states())
self.assertFalse(a.allTransitions())
def test_initialState(self):
"""
L{Automaton.initialState} is a descriptor that sets the initial
state if it's not yet set, and raises L{ValueError} if it is.
"""
a = Automaton()
a.initialState = "a state"
self.assertEqual(a.initialState, "a state")
with self.assertRaises(ValueError):
a.initialState = "another state"
# FIXME: addTransition for transition that's been added before
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