def test_updating():
s1 = State()
s2 = State()
t = Transition(s2, 'b', Direction.RIGHT)
s1.add_transition('a', t)
tm = TuringMachine("acd", s1, s2, s1)
assert tm.tape == ['a', 'c', 'd', '_']
tm._read('a')
assert tm.tape[0] == 'b'
assert tm.current_state == s2
def test_tape_never_negative():
s1 = State()
s2 = State()
t = Transition(s2, 'b', Direction.LEFT)
s1.add_transition('a', t)
tm = TuringMachine("acd", s1, s2, s1)
assert tm.tape == ['a', 'c', 'd', '_']
tm._read('a')
assert tm.tape[0] == 'b'
assert tm.current_state == s2
assert tm.tape_position == 0
def test_example_spec_aab_manually():
q0, q1, qa, qr = create_example_from_spec()
tm = TuringMachine('aab', qa, qr, q0)
assert tm.tape == ['a', 'a', 'b', '_']
#tm.begin()
tm._read('a')
assert tm.tape_position == 1
assert tm.current_state == q0
tm._read('a')
assert tm.tape_position == 2
assert tm.current_state == q0
tm._read('b')
assert tm.tape_position == 3
assert tm.tape == ['a', 'a', 'b', '_']
assert tm.current_state == q1
tm._read('_')
assert tm.tape_position == 2
assert tm.tape == ['a', 'a', 'b', 'b', '_']
assert tm.current_state == qa
assert tm.accept()