def test_get_next_end_of_items():
p = PreviousArray()
assert p.get_next() is None
def test_get_next_one_item_in_list():
p = PreviousArray()
p.append('apple')
assert p.get_next() == 'apple'
def prev():
p = PreviousArray()
p.append("one")
p.append("two")
p.append("three")
yield p
def test_empty_item_list_get_first_returns_none():
p = PreviousArray()
assert p.get_first() is None
def test_get_previous_two_items():
p = PreviousArray()
p.append("one")
p.append("two")
assert p.get_previous() == 'one'
def test_get_previous_one_item():
p = PreviousArray()
p.append("one")
assert p.get_previous() == 'one'
def test_get_previous_no_items():
p = PreviousArray()
assert p.get_previous() is None
def test_append():
p = PreviousArray()
p.append("hello")
assert len(p.items) == 1
assert p.items[0] == 'hello'
def test_initialize():
p = PreviousArray()
assert p.prev_index is None
assert len(p.items) == 0