Python unittest – assertAlmostEqual()函数

Python中的assertAlmostEqual () 是一个 unittest 库函数，用于在单元测试中检查两个给定值是否几乎相等。该函数将五个参数作为输入，并根据断言条件返回一个布尔值。

此函数通过计算差异、四舍五入到给定的小数位数（默认为 7）并与零比较来检查first和second是否近似相等。

如果提供delta而不是places ，则first和second之间的差必须小于或等于delta 。

Syntax: assertAlmostEqual(first, second, places=7, message=None, delta=None)

Parameters: assertAlmostEqual() accept three parameters which are listed below with explanation:

first: first input value (integer)
second: second input value (integer)
places: decimal places for approximation
message: a string sentence as a message which got displayed when the test case got failed.
delta: delta value for approximation

编程需要懂一点英语

下面列出了两个不同的示例，说明了给定断言函数的正负测试用例：

例子：

Python3

# test suite
import unittest
  
  
class TestStringMethods(unittest.TestCase):
    # negative test function to test if values are almost equal with place
    def test_negativeWithPlaces(self):
        first = 4.4555
        second = 4.4566
        decimalPlace = 3
        # error message in case if test case got failed
        message = "first and second are not almost equal."
        # assert function() to check if values are almost equal
        self.assertAlmostEqual(first, second, decimalPlace, message)
  
    # positive test function to test if values are almost equal with place
    def test_positiveWithPlaces(self):
        first = 4.4555
        second = 4.4566
        decimalPlace = 2
        # error message in case if test case got failed
        message = "first and second are not almost equal."
        # assert function() to check if values are almost equal
        self.assertAlmostEqual(first, second, decimalPlace, message)
  
    # negative test function to test if values are almost equal with delta
    def test_negativeWithDelta(self):
        first = 4.4555
        second = 4.4566
        delta = 0.0001
        # error message in case if test case got failed
        message = "first and second are not almost equal."
        # assert function() to check if values are almost equal
        self.assertAlmostEqual(first, second, None, message, delta)
  
    # positive test function to test if values are almost equal with delta
    def test_positiveWithDelta(self):
        first = 4.4555
        second = 4.4566
        delta = 0.002
        # error message in case if test case got failed
        message = "first and second are not almost equal."
        # assert function() to check if values are almost equal
        self.assertAlmostEqual(first, second, None, message, delta)
  
  
if __name__ == '__main__':
    unittest.main()

输出：

FF..
======================================================================
FAIL: test_negativeWithDelta (__main__.TestStringMethods)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/2c36bbd2c940a6c7b81a901ebfdd2ad8.py", line 34, in test_negativeWithDelta
    self.assertAlmostEqual(first, second, None, message, delta)
AssertionError: 4.4555 != 4.4566 within 0.0001 delta : first and second are not almost equal.

======================================================================
FAIL: test_negativeWithPlaces (__main__.TestStringMethods)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/2c36bbd2c940a6c7b81a901ebfdd2ad8.py", line 14, in test_negativeWithPlaces
    self.assertAlmostEqual(first, second, decimalPlace, message)
AssertionError: 4.4555 != 4.4566 within 3 places : first and second are not almost equal.

----------------------------------------------------------------------
Ran 4 tests in 0.001s

FAILED (failures=2)

参考：https://docs。 Python.org/3/library/unittest.html