测试递归Python函数

您始终可以实现一个类来封装状态,并为您提供更大的灵活性,下面是一个示意图:

>>> class MockBoolCheck:
...     def __init__(self, fail_after=0):
...         self.count = 0
...         self.fail_after = fail_after
...     def __call__(self, n):
...         called = self.count
...         self.count += 1
...         return called <= self.fail_after
...
>>> bool_function = MockBoolCheck()
>>> bool_function(42)
True
>>> bool_function(42)
False
>>> bool_function(42)
False
>>> bool_function(42)
False
>>> bool_function(42)
False

# Your code (or module):

def bool_function(n):
    print('REAL bool-function {}'.format(n))
    return n <= 0

def factorial(n):
    print('FACT {}'.format(n))
    if bool_function(n):
        return 1
    else:
        return n * factorial(n-1)

# Mocking code (or module):

def mock_function(n):
    print('MOCK bool-function {}'.format(n))
    global bool_function
    bool_function = bool_func_orig  # restore on the first use
    return False
bool_func_orig = bool_function
bool_function = mock_function  # mock it

# Go run it!
factorial(10)

如果这是两个独立的模块,则 global bool_function & bool_function=... somemodule.bool_function=... .

如果您想使用mocking库,那么这取决于您使用的库。如果是这样的话 unittest.mock ,那么你应该玩 side_effect=... wraps=... (参见 manual ). 同样的方法:模仿它,并在第一次使用时从副作用内部取消模仿。

def factorial(n, debug=False):
  if bool_function(n) or debug:
      return 1
  else:
      return n * factorial(n-1)

这自然意味着您也在进行外部测试 bool_function()

只需将函数作为参数传递。如果函数为None,您可以根据需要应用一些默认行为。

这是在 queries to iterables (例如Django查询或Peewee查询)在大多数语言中。

返回布尔值的函数通常称为 predicate

def factorial(n, predicate=None):
  if not predicate:
     predicate = lambda x: x > 2

  if predicate(n):
      return 1
  else:
      return n * factorial(n-1)

对于python>3.6

import mock   
class RecursividadeTest(unittest.TestCase):
    def test_recursive(self):
        with mock.patch('path.factorial') as mock_fact:
            factorial(3)
            self.assertTrue(mock_fact.called)
            self.assertGreaterEqual(mock_fact.call_count, 2)

    def test_recursive_2(self):
    with mock.patch('incolumepy.sequences.fibonacci.fibonacci') as mock_fib:
        for i in range(1, 5, -1):
            expected = i - 1
            fibonacci(i)
            self.assertTrue(mock_fib.called)
            self.assertEqual(mock_fib.call_count, expected)