Selenium2+python自动化56-unittest之断言（assert）

前言

在测试用例中，执行完测试用例后，最后一步是判断测试结果是pass还是fail，自动化测试脚本里面一般把这种生成测试结果的方法称为断言（assert）。

用unittest组件测试用例的时候，断言的方法还是很多的，下面介绍几种常用的断言方法：assertEqual、assertIn、assertTrue

 selenium+python高级教程》已出书：selenium webdriver基于Python源码案例

（购买此书送对应PDF版本）

 

一、简单案例

1.下面写了4个case，其中第四个是执行失败的

# coding:utf-8
import unittest
class Test(unittest.TestCase):
    def test01(self):
        '''判断 a == b '''
        a = 1
        b = 1
        self.assertEqual(a, b)

    def test02(self):
        '''判断 a in b '''
        a = "hello"
        b = "hello world!"
        self.assertIn(a, b)

    def test03(self):
        '''判断 a is True '''
        a = True
        self.assertTrue(a)

    def test04(self):
        '''失败案例'''
        a = "上海-悠悠"
        b = "yoyo"
        self.assertEqual(a, b)

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

2.执行结果如下

Failure
Expected :'\xe4\xb8\x8a\xe6\xb5\xb7-\xe6\x82\xa0\xe6\x82\xa0'
Actual   :'yoyo'
 <Click to see difference>

Traceback (most recent call last):
  File "D:\test\yoyotest\kecheng\test12.py", line 27, in test04
    self.assertEqual(a, b)
AssertionError: '\xe4\xb8\x8a\xe6\xb5\xb7-\xe6\x82\xa0\xe6\x82\xa0' != 'yoyo'
3.执行的结果，中文编码不对，没正常显示中文，遇到这种情况，可以自定义异常输出

 

二、自定义异常

1.以assertEqual为例分析：

assertEqual(self, first, second, msg=None)
    Fail if the two objects are unequal as determined by the '=='
    operator.

2.翻译：如果两个对象不能相等，就返回失败，相当于return: first==second

3.这里除了相比较的两个参数first和second，还有第三个参数msg=None,这个msg参数就是遇到异常后自定义输出信息

 

三、unittest常用的断言方法

1.assertEqual(self, first, second, msg=None)

--判断两个参数相等：first == second

2.assertNotEqual(self, first, second, msg=None)

--判断两个参数不相等：first ！= second

3.assertIn(self, member, container, msg=None)

--判断是字符串是否包含：member in container

4.assertNotIn(self, member, container, msg=None)

--判断是字符串是否不包含：member not in container

5.assertTrue(self, expr, msg=None)

--判断是否为真：expr is True

6.assertFalse(self, expr, msg=None)

--判断是否为假：expr is False

7.assertIsNone(self, obj, msg=None)

--判断是否为None：obj is None

8.assertIsNotNone(self, obj, msg=None)
--判断是否不为None：obj is not None

四、unittest所有断言方法

1.下面是unittest框架支持的所有断言方法，有兴趣的同学可以慢慢看。

|  assertAlmostEqual(self, first, second, places=None, msg=None, delta=None)
|      Fail if the two objects are unequal as determined by their
|      difference rounded to the given number of decimal places
|      (default 7) and comparing to zero, or by comparing that the
|      between the two objects is more than the given delta.
|      
|      Note that decimal places (from zero) are usually not the same
|      as significant digits (measured from the most signficant digit).
|      
|      If the two objects compare equal then they will automatically
|      compare almost equal.
|  
|  assertAlmostEquals = assertAlmostEqual(self, first, second, places=None, msg=None, delta=None)
|  
|  assertDictContainsSubset(self, expected, actual, msg=None)
|      Checks whether actual is a superset of expected.
|  
|  assertDictEqual(self, d1, d2, msg=None)
|  
|  assertEqual(self, first, second, msg=None)
|      Fail if the two objects are unequal as determined by the '=='
|      operator.
|  
|  assertEquals = assertEqual(self, first, second, msg=None)
|  
|  assertFalse(self, expr, msg=None)
|      Check that the expression is false.
|  
|  assertGreater(self, a, b, msg=None)
|      Just like self.assertTrue(a > b), but with a nicer default message.
|  
|  assertGreaterEqual(self, a, b, msg=None)
|      Just like self.assertTrue(a >= b), but with a nicer default message.
|  
|  assertIn(self, member, container, msg=None)
|