def test_iterable():
    """
    PDeques can be created from iterables even though they can't be len()
    hinted.
    """

    assert pdeque(iter("a")) == pdeque(iter("a"))

def test_comparison():
    small = pdeque([1, 2])
    large = pdeque([1, 2, 3])

    assert small < large
    assert large > small
    assert not small > large
    assert not large < small
    assert large != small

    # Not equal to other types
    assert small != [1, 2]

def test_indexing():
    assert pdeque([1, 2, 3])[0] == 1
    assert pdeque([1, 2, 3])[1] == 2
    assert pdeque([1, 2, 3])[2] == 3
    assert pdeque([1, 2, 3])[-1] == 3
    assert pdeque([1, 2, 3])[-2] == 2
    assert pdeque([1, 2, 3])[-3] == 1

def test_indexing_out_of_range():
    with pytest.raises(IndexError):
        pdeque([1, 2, 3])[-4]

    with pytest.raises(IndexError):
        pdeque([1, 2, 3])[3]

    with pytest.raises(IndexError):
        pdeque([2])[-2]

def test_popleft():
    x = pdeque([1, 2, 3, 4]).popleft()
    assert x.left == 2
    assert x.right == 4

    x = x.popleft()
    assert x.left == 3
    assert x.right == 4

    x = x.popleft()
    assert x.right == 4
    assert x.left == 4

    x = x.popleft()
    assert x == pdeque()

    x = pdeque([1, 2]).popleft()
    assert x == pdeque([2])

    x = x.popleft()
    assert x == pdeque()

    assert pdeque().append(1).popleft() == pdeque()
    assert pdeque().appendleft(1).popleft() == pdeque()

def test_left_on_empty_deque():
    with pytest.raises(IndexError):
        pdeque().left

def test_pop_multiple():
    assert pdeque([1, 2, 3, 4]).pop(3) == pdeque([1])
    assert pdeque([1, 2]).pop(3) == pdeque()

def test_literalish():
    assert dq(1, 2, 3) == pdeque([1, 2, 3])

def test_hashing():
    assert hash(pdeque([1, 2, 3])) == hash(pdeque().append(1).append(2).append(3))

def test_indexing_invalid_type():
    with pytest.raises(TypeError) as e:
        pdeque([1, 2, 3])['foo']

    assert 'cannot be interpreted' in str(e)

def test_count():
    x = pdeque([1, 2, 3, 2, 1])
    assert x.count(1) == 2
    assert x.count(2) == 2

def test_extendleft_with_maxlen():
    assert pdeque([1, 2], maxlen=3).extendleft([3, 4]) == pdeque([4, 3, 1])
    assert pdeque([1, 2], maxlen=2).extendleft([3, 4]) == pdeque([4, 3])
    assert pdeque([], maxlen=2).extendleft([1, 2]) == pdeque([2, 1])
    assert pdeque([], maxlen=0).extendleft([1, 2]) == pdeque([])

def test_extendleft():
    assert pdeque([2, 1]).extendleft([3, 4]) == pdeque([4, 3, 2, 1])

def test_extend_with_maxlen():
    assert pdeque([1, 2], maxlen=3).extend([3, 4]) == pdeque([2, 3, 4])
    assert pdeque([1, 2], maxlen=2).extend([3, 4]) == pdeque([3, 4])
    assert pdeque([], maxlen=2).extend([1, 2]) == pdeque([1, 2])
    assert pdeque([], maxlen=0).extend([1, 2]) == pdeque([])

def test_extend():
    assert pdeque([1, 2]).extend([3, 4]) == pdeque([1, 2, 3, 4])

def test_construction_with_maxlen():
    assert pdeque([1, 2, 3, 4], maxlen=2) == pdeque([3, 4])
    assert pdeque([1, 2, 3, 4], maxlen=4) == pdeque([1, 2, 3, 4])
    assert pdeque([], maxlen=2) == pdeque()

def test_pickling():
    input = pdeque([1, 2, 3], maxlen=5)
    output = pickle.loads(pickle.dumps(input, -1))

    assert output == input
    assert output.maxlen == input.maxlen

def test_remove():
    assert pdeque([1, 2, 3, 4]).remove(2) == pdeque([1, 3, 4])
    assert pdeque([1, 2, 3, 4]).remove(4) == pdeque([1, 2, 3])

    # Right list must be reversed before removing element
    assert pdeque([1, 2, 3, 3, 4, 5, 4, 6]).remove(4) == pdeque([1, 2, 3, 3, 5, 4, 6])

def test_slicing():
    assert pdeque([1, 2, 3])[1:2] == pdeque([2])
    assert pdeque([1, 2, 3])[2:1] == pdeque([])
    assert pdeque([1, 2, 3])[-2:-1] == pdeque([2])
    assert pdeque([1, 2, 3])[::2] == pdeque([1, 3])

def test_remove_element_missing():
    with pytest.raises(ValueError):
        pdeque().remove(2)

    with pytest.raises(ValueError):
        pdeque([1, 2, 3]).remove(4)