unittest框架系列四（子测试subTest）

子测试subTest

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–成都-阿木木

如果测试方法内，还需要对某些差异非常小的参数进行测试，unittest支持使用subTest()上下文管理器在测试方法的内部区分他们，也就是说，我们可以在测试方法的内部进行调用的测试方法的测试，也就是测试方法嵌套，可以传递一个参数集（数据驱动）对于子测试方法进行测试，子测试方法会针对参数集（数据驱动）中的每一个参数值，进行测试结果的输出。

class NumbersTest(unittest.TestCase):

    def test_even(self):
        """
        Test that numbers between 0 and 5 are all even.
        """
        for i in range(0, 6):
            with self.subTest(i=i):
                self.assertEqual(i % 2, 0)

结果为：
======================================================================
FAIL: test_even (__main__.NumbersTest) (i=1)
Test that numbers between 0 and 5 are all even.
----------------------------------------------------------------------
Traceback (most recent call last):
  File "D:/TestScriptDir/python_web/mysite/unittest_demo.py", line 25, in test_even
    self.assertEqual(i % 2, 0)
AssertionError: 1 != 0

======================================================================
FAIL: test_even (__main__.NumbersTest) (i=3)
Test that numbers between 0 and 5 are all even.
----------------------------------------------------------------------
Traceback (most recent call last):
  File "D:/TestScriptDir/python_web/mysite/unittest_demo.py", line 25, in test_even
    self.assertEqual(i % 2, 0)
AssertionError: 1 != 0

======================================================================
FAIL: test_even (__main__.NumbersTest) (i=5)
Test that numbers between 0 and 5 are all even.
----------------------------------------------------------------------
Traceback (most recent call last):
  File "D:/TestScriptDir/python_web/mysite/unittest_demo.py", line 25, in test_even
    self.assertEqual(i % 2, 0)
AssertionError: 1 != 0

----------------------------------------------------------------------
Ran 1 test in 0.001s

FAILED (failures=3)

如果不使用子测试，则在第一次失败后执行将停止，并且错误将不那么容易诊断，因为i 不会显示的值：

FAIL: test_even (__main__.NumbersTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "subtests.py", line 32, in test_even
    self.assertEqual(i % 2, 0)
AssertionError: 1 != 0