def test_element_holds_value(self):

new_element = Element(20)

self.assertEqual(new_element.value, 20)

def test_element_holds_next_element(self):

first_element = Element(1)

second_element = Element('some string')

first_element.next_node = second_element

def test_empty_list_has_no_head(self):

list = LinkedList()

self.assertIs(list.head, None)

def test_empty_list_has_no_tail(self):

list = LinkedList()

self.assertIs(list.tail, None)

def test_push_element_to_list(self):

list = LinkedList()

list.push(50)

self.assertEqual(list.to_array(), [50])

def test_push_multiple_elements_to_list(self):

list = LinkedList()

list.push(50).push(1).push(20).push([1, 2, 3]).push('hello')

self.assertEqual(list.to_array(), [50, 1, 20, [1, 2, 3], 'hello'])

def test_push_existing_elements_to_list(self):

list = LinkedList()

first_element = Element([1, 2, 3])

second_element = Element('cool')

list.push(first_element).push(second_element)

self.assertEqual(list.to_array(), [[1, 2, 3], 'cool'])

def test_populated_list_has_head(self):

list = LinkedList()

list.push(5)

self.assertEqual(list.head.value, 5)

def test_populated_list_has_tail(self):

list = LinkedList()

list.push(5).push(10)

self.assertEqual(list.tail.value, 10)

def test_populated_list_has_size(self):

list = LinkedList()

list.push(5).push(10).push(20)

self.assertEqual(len(list), 3)

def convert_list_to_string(self):

list = LinkedList()

list.push(20).push(10).push([1, 2, 3])

self.assertEqual(str(list), '( 20 ) -> ( 10 ) -> ( [1, 2, 3] ) -> ')

def test_unshift_list(self):

list = LinkedList()

list.unshift(5)

self.assertEqual(list.head.value, 5)

def test_unshift_multiple_elements(self):

list = LinkedList()

list.unshift(5).unshift([1, 2, 3]).unshift('hello')

self.assertEqual(list.to_array(), ['hello', [1, 2, 3], 5])

def test_pop_list(self):

list = LinkedList()

list.push(5).push(10).push(20)

self.assertEqual(list.pop().value, 20)

def test_shift_list(self):

list = LinkedList()

list.push(5).push(10).push(20)

self.assertEqual(list.shift().value, 5)

def test_list_len_with_push_pop_unshift_and_shift(self):

list = LinkedList()

list.push(5).push(10).push(20).push(50).unshift(44)

list.pop()

list.shift()

self.assertEqual(len(list), 3)

def test_get_element_at_index(self):

list = LinkedList()

list.push(5).push(10).push(20).push(50)

self.assertEqual(list.at(2).value, 20)

def test_get_element_at_first_index(self):

list = LinkedList()

list.push(5).push(10).push(20).push(50)

self.assertEqual(list.at(0).value, 5)

def test_get_element_at_last_index(self):

list = LinkedList()

list.push(5).push(10).push(20).push(50)

self.assertEqual(list.at(-1).value, 50)

def test_get_element_at_negative_index(self):

list = LinkedList()

list.push(5).push(10).push(20).push(50)

self.assertEqual(list.at(-3).value, 10)

def test_get_element_at_negative_index(self):

list = LinkedList()

list.push(5).push(10).push(20).push(50)

self.assertEqual(list.at(-3).value, 10)

def test_get_element_at_invalid_index(self):

list = LinkedList()

list.push(5).push(10).push(20).push(50)

self.assertIs(list.at(10), None)

def test_get_element_at_invalid_negative_index(self):

list = LinkedList()

list.push(5).push(10).push(20).push(50)

self.assertIs(list.at(-10), None)

def test_finding_element_index(self):

list = LinkedList()

list.push(5).push(10).push(20).push(50)

self.assertEqual(list.find(5), 0)

def test_finding_non_existant_element(self):

list = LinkedList()

list.push(5).push(10).push(20).push(50)

self.assertIs(list.find(4), None)

def test_is_element_in_list(self):

list = LinkedList()

list.push(5).push(10).push(20)

self.assertIs(list.is_containing(5), True)

def test_is_element_not_in_list(self):

list = LinkedList()

list.push(5).push(10).push(20)

self.assertIs(list.is_containing(4), False)

def test_insert_element_at_index(self):

list = LinkedList()

list.push(5).push(10).push(20)

list.insert_at('cool', 1)

self.assertEqual(list.to_array(), [5, 'cool', 10, 20])

def test_insert_element_at_first_index(self):

list = LinkedList()

list.push(5).push(10).push(20)

list.insert_at('cool', 0)

self.assertEqual(list.to_array(), ['cool', 5, 10, 20])

def test_insert_element_at_last_index(self):

list = LinkedList()

list.push(5).push(10).push(20)

list.insert_at('cool', -1)

self.assertEqual(list.to_array(), [5, 10, 20, 'cool'])

def test_insert_element_at_non_existing_index(self):

list = LinkedList()

list.push(5).push(10).push(20)

list.insert_at('cool', 10)

self.assertEqual(list.to_array(), [5, 10, 20])

def test_insert_element_at_negative_index(self):

list = LinkedList()

list.push(5).push(10).push(20)

list.insert_at('cool', -2)

self.assertEqual(list.to_array(), [5, 10, 'cool', 20])

def test_insert_at_multiple_elements(self):

list = LinkedList()

list.push(5).push(10).push(20).push(40).push([55, 66, 77])

list.insert_at('first', 0).insert_at('second', 3).insert_at('rain', -1)

self.assertEqual(list.to_array(), ['first', 5, 10, 'second', 20, 40, [55, 66, 77], 'rain'])

def test_remove_element_at_index(self):

list = LinkedList()

list.push(5).push(10).push(20)

list.remove_at(1)

self.assertEqual(list.to_array(), [5, 20])

def test_remove_element_at_head(self):

list = LinkedList()

list.push(5).push(10).push(20)

list.remove_at(0)

self.assertEqual(list.to_array(), [10, 20])

def test_remove_element_at_tail(self):

list = LinkedList()

list.push(5).push(10).push(20)

list.remove_at(-1)

self.assertEqual(list.to_array(), [5, 10])

def test_remove_element_at_negative_index(self):

list = LinkedList()

list.push(5).push(10).push(20).push(40)

list.remove_at(-3)

self.assertEqual(list.to_array(), [5, 20, 40])

def test_remove_multiple_elements(self):

list = LinkedList()

list.push(5).push(10).push(20).push(40).push([55, 66, 77])

list.remove_at(0).remove_at(1).remove_at(-1)

self.assertEqual(list.to_array(), [10, 40])

def test_reverse_list(self):

list = LinkedList()

list.push(5).push(10).push(20).push(40).push([55, 66, 77])