def test_given_reference_followed_by_reference_then_lookahead_is_first_set(
self) -> None:
grammar = Grammar(Rule('A', ['B', 'X']), Rule('B', ['x']),
Rule('X', ['a']), Rule('X', ['b']))
state = RuleState(0, 0, {'x'})
self.assertEqual({RuleState(1, 0, {'a', 'b'})},
state.follow_states(grammar))
def test_given_last_unprocessed_reference_then_lookaheads_of_parent(
self) -> None:
grammar = Grammar(Rule('A', ['x', 'B']), Rule('A', ['B', 'x']),
Rule('B', ['x']))
state = RuleState(0, 1, {'a'})
self.assertEqual({RuleState(2, 0, {'a'})},
state.follow_states(grammar))
def test_given_reference_followed_by_recursion_then_lookahead_is_first_set(
self) -> None:
grammar = Grammar(Rule('X', ['a']), Rule('X', ['b', 'X', 'X']))
state = RuleState(1, 1, {'x'})
expected = {RuleState(0, 0, {'a', 'b'}), RuleState(1, 0, {'a', 'b'})}
self.assertEqual(expected, state.follow_states(grammar))
def test_given_unprocessed_reference_then_initial_reference_states(
self) -> None:
grammar = Grammar(Rule('A', ['B']), Rule('B', ['b']))
state = RuleState(0, 0, {'b'})
self.assertEqual({RuleState(1, 0, {'b'})},
state.follow_states(grammar))
def test_given_unprocessed_terminal_then_no_follow_states(self) -> None:
grammar = Grammar(Rule('A', ['a']))
state = RuleState(0, 0, {'a'})
self.assertEqual(set(), state.follow_states(grammar))
