def test_balanced_tail_closed_returns_0():
"""Test that a list with a closed tail returns 0."""
new_list = DoubleLink(')()(')
assert new_list.tail.value == ')'
assert new_list.balanced() == 0
def test_balanced_empty_list():
"""Test that an empty list returns a value error."""
new_list = DoubleLink()
with pytest.raises(ValueError):
new_list.balanced()
def test_balanced_tail_open():
"""Test that a list with an open tail returns 1."""
new_list = DoubleLink('(()(')
assert new_list.tail.value == '('
assert new_list.balanced() == 1
def test_balanced_first_node_closed_paren():
"""Check that balanced returns -1 when head is ')'."""
new_list = DoubleLink('()')
assert new_list.balanced() == -1