断言整数在范围内

Question

我正在python中编写一些单元测试,测试是否收到整数.然而,有时这个整数可以关闭1或2,我真的不在乎.基本上我希望能够断言收到的整数在一定范围内,如:

self.assertBetween(998, 1000, my_integer)

这是否有可接受的方式？或者我必须做这样的事情:

self.assertTrue(998 <= my_integer)
self.assertTrue(my_integer <= 1000)

编辑 到目前为止的答案建议:

self.assertTrue(998 <= my_integer <= 1000)

在我的2个断言的例子中,这有什么好处吗？

Answer 1

您可以使用" 链式比较 ":

self.assertTrue(998 <= my_integer <= 1000)

Answer 2

Python有一个可用于此的内置函数:assertAlmostEqual.

self.assertAlmostEqual(myinteger, 999, delta=1)
# is equivalent to
self.assertTrue(998 <= myinteger <= 1000)
# ... but gives better error messages.

可选参数delta指定与您正在测试的值的允许距离.

Answer 3

我不认为使用assertTrue内部比较是一个好主意- 这样你就失去了FAIL消息中的任何信息:

AssertionError: False is not true

这根本没有帮助,你基本上回到"原始" assert,你正在失去很多unittest方法的好处.

我会建议:

创建自己的自定义断言

在其中您可以打印更有意义的消息.例如:

import unittest

class BetweenAssertMixin(object):
    def assertBetween(self, x, lo, hi):
        if not (lo <= x <= hi):
            raise AssertionError('%r not between %r and %r' % (x, lo, hi))

class Test1(unittest.TestCase, BetweenAssertMixin):
    def test_between(self):
        self.assertBetween(999, 998, 1000)

    def test_too_low(self):
        self.assertBetween(997, 998, 1000)

    def test_too_high(self):
        self.assertBetween(1001, 998, 1000)

if __name__ == '__main__':
    unittest.main()

然后你将有以下输出(缩短):

======================================================================
FAIL: test_too_high (__main__.Test1)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "example.py", line 19, in test_too_high
    self.assertBetween(1001, 998, 1000)
  File "example.py", line 8, in assertBetween
    raise AssertionError('%r is not between %r and %r' % (x, lo, hi))
AssertionError: 1001 is not between 998 and 1000
======================================================================
FAIL: test_too_low (__main__.Test1)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "example.py", line 16, in test_too_low
    self.assertBetween(997, 998, 1000)
  File "example.py", line 8, in assertBetween
    raise AssertionError('%r is not between %r and %r' % (x, lo, hi))
AssertionError: 997 is not between 998 and 1000
----------------------------------------------------------------------

或者使用assertLessEqual和assertGreaterEqual

如果你不想要自定义断言(它确实添加了另一个回溯记录和几行代码):

...
def test_no_custom_assert(self):
    my_integer = 100
    self.assertGreaterEqual(my_integer, 998)
    self.assertLessEqual(my_integer, 1000)
...

这有点长(如果它只使用一次,它可能比添加自定义断言的总长度短)assertTrue(998 <= my_integer <= 1000)但是你仍然会得到很好的失败消息(也没有额外的回溯记录):

======================================================================
FAIL: test_no_custom_assert (__main__.Test1)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "example.py", line 23, in test_no_custom_assert
    self.assertGreaterEqual(my_integer, 998)
AssertionError: 100 not greater than or equal to 998