def test_len_returns_the_size_of_the_array(self):
da = DynamicArray()
expected_result = 0
result = len(da)
self.assertEqual(result, expected_result)
expected_result = 1
da._n = 1
result = len(da)
self.assertEqual(result, expected_result)
def test_insert_doubles_array_capacity_if_capacity_reached(self):
da = DynamicArray()
da._n = 2
da._capacity = 2
da._A = da._make_array(da._capacity)
da._A[0:2] = ['foo', 'bar']
expected_result = 4
da.insert(0, 'spam')
result = da._capacity
self.assertEqual(result, expected_result)
def test_remove_removes_first_occurence_of_value_in_array(self):
da = DynamicArray()
da._n = 5
da._capacity = 5
da._A = da._make_array(da._capacity)
da._A[0:5] = ['foo', 'bar', 'spam', 'baz', 'spam']
expected_elements = ['foo', 'bar', 'baz', 'spam']
da.remove('spam')
self.assertEqual(da._A[0:4], expected_elements)
self.assertEqual(da._n, 4)
def test_insert_adds_at_index_shifts_items_rightward_with_positive_index(
self):
da = DynamicArray()
da._n = 3
da._capacity = 4
da._A = da._make_array(da._capacity)
elements = ['foo', 'bar', 'baz']
da._A[0:3] = elements
expected_elements = ['foo', 'spam', 'bar', 'baz']
da.insert(1, 'spam')
self.assertEqual(da._A[0:5], expected_elements)
def test_remove_raises_ValueError_with_value_missing_in_array(self):
da = DynamicArray()
da._n = 2
da._capacity = 2
da._A = da._make_array(da._capacity)
da._A[0:2] = ['foo', 'bar']
self.assertRaises(ValueError, da.remove, 'spam')
def test_pop_removes_and_returns_last_element_of_array(self):
da = DynamicArray()
da._n = 3
da._capacity = 3
da._A = da._make_array(da._capacity)
da._A[0:3] = ['foo', 'bar', 'baz']
result = da.pop()
self.assertEqual(result, 'baz')
self.assertEqual(da._A[0:2], ['foo', 'bar'])
self.assertEqual(da._n, 2)
def test_getitem_returns_correct_element_at_positive_index(self):
expected_result = 'bar'
elements = ['foo', expected_result, 'baz']
da = DynamicArray()
da._n = 3
da._capacity = 4
da._A = da._make_array(da._capacity)
da._A[0:3] = elements
result = da[1]
self.assertEqual(result, expected_result)
def test_getitem_raises_IndexError_with_invalid_index(self):
# Invalid index in an empty array:
da = DynamicArray()
self.assertRaises(IndexError, da.__getitem__, 0)
# Invalid positive index in a non-empty array:
da._capacity = 4
da._n = 3
da._A = da._make_array(da._capacity)
da._A[0:3] = [None] * 3
self.assertRaises(IndexError, da.__getitem__, 3)
# Invalid negative index in a non-empty array:
self.assertRaises(IndexError, da.__getitem__, -4)
def test_append_adds_object_at_end_of_array(self):
da = DynamicArray()
expected_result = 'foo'
da.append(expected_result)
self.assertEqual(da._A[-1], expected_result)
self.assertEqual(da._n, 1)
expected_result = 'bar'
da.append(expected_result)
self.assertEqual(da._A[-1], expected_result)
self.assertEqual(da._n, 2)
def test_pop_halves_array_capacity_if_less_than_quarter_of_capacity_used(
self):
da = DynamicArray()
da._capacity = 64
da._n = 17
da._A = da._make_array(da._capacity)
da._A[0:17] = [None] * 17
# first pop() should not shrink the array, since with 16 elements
# we have not passed the N/4 threshold.
da.pop()
self.assertEqual(da._capacity, 64)
# second pop() should trigger halving the array capacity:
da.pop()
self.assertEqual(da._capacity, 32)
def test_pop_raises_Empty_exception_if_array_is_empty(self):
da = DynamicArray()
self.assertRaises(Empty, da.pop)
def test_remove_halves_array_capacity_if_less_than_quarter_of_capacity_used(
self):
da = DynamicArray()
da._capacity = 64
da._n = 17
da._A = da._make_array(da._capacity)
da._A[0:17] = [l for l in 'abcdefghijklmnopq']
# first remove() should not shrink the array, since with 16 elements
# we have not passed the N/4 threshold.
da.remove('a')
self.assertEqual(da._capacity, 64)
# second remove() should trigger halving the array capacity:
da.remove('q')
self.assertEqual(da._capacity, 32)