def test_node_with_several_remaining_values_is_returned_repeatedly_until_exhausted(
self):
unexhausted_node_one = new_unexhausted_mock_node(
"A", remaining_value_count=2)
unexhausted_node_two = new_unexhausted_mock_node(
"B", remaining_value_count=3)
stack = _SearchGraphNodeStack()
stack.push(unexhausted_node_one)
stack.push(new_exhausted_mock_node("C"))
stack.push(unexhausted_node_two)
self.assertIs(stack.backtrack_to_first_unexhausted_node(),
unexhausted_node_two)
self.assertIs(stack.backtrack_to_first_unexhausted_node(),
unexhausted_node_two)
self.assertIs(stack.backtrack_to_first_unexhausted_node(),
unexhausted_node_two)
self.assertIs(stack.backtrack_to_first_unexhausted_node(),
unexhausted_node_one)
self.assertIs(stack.backtrack_to_first_unexhausted_node(),
unexhausted_node_one)
self.assertIsNone(stack.backtrack_to_first_unexhausted_node())
def test_backtrack_with_stack_containing_only_exhausted_nodes_returns_none(
self):
stack = _SearchGraphNodeStack()
stack.push(new_exhausted_mock_node())
stack.push(new_exhausted_mock_node())
stack.push(new_exhausted_mock_node())
self.assertIsNone(stack.backtrack_to_first_unexhausted_node())
def test_backtrack_with_stack_containing_two_or_more_unexhausted_nodes_returns_the_topmost_unexhausted_node(
self):
unexhausted_node_one = new_unexhausted_mock_node()
unexhausted_node_two = new_unexhausted_mock_node()
stack = _SearchGraphNodeStack()
stack.push(new_exhausted_mock_node())
stack.push(new_exhausted_mock_node())
stack.push(unexhausted_node_one)
stack.push(unexhausted_node_two)
self.assertIs(stack.backtrack_to_first_unexhausted_node(),
unexhausted_node_two)
def test_backtracking_preserves_lifo_semantics(self):
unexhausted_node_one = new_unexhausted_mock_node("A")
unexhausted_node_two = new_unexhausted_mock_node("B")
unexhausted_node_three = new_unexhausted_mock_node("C")
stack = _SearchGraphNodeStack()
stack.push(new_exhausted_mock_node("D"))
stack.push(new_exhausted_mock_node("E"))
stack.push(unexhausted_node_one)
stack.push(unexhausted_node_two)
stack.push(new_exhausted_mock_node("F"))
stack.push(unexhausted_node_three)
self.assertIs(stack.backtrack_to_first_unexhausted_node(),
unexhausted_node_three)
self.assertIs(stack.backtrack_to_first_unexhausted_node(),
unexhausted_node_two)
self.assertIs(stack.backtrack_to_first_unexhausted_node(),
unexhausted_node_one)
self.assertIsNone(stack.backtrack_to_first_unexhausted_node())
def test_backtrack_with_empty_virgin_stack_returns_none(self):
stack = _SearchGraphNodeStack()
self.assertIsNone(stack.backtrack_to_first_unexhausted_node())