六：Python断言方法：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

基本断言方法

基本的断言方法提供了测试结果是True还是False。所有的断言方法都有一个msg参数，如果指定msg参数的值，则将该信息作为失败的错误信息返回。

序号	断言方法	断言描述
1	assertEqual(arg1, arg2, msg=None)	验证arg1=arg2，不等则fail
2	assertNotEqual(arg1, arg2, msg=None)	验证arg1 != arg2, 相等则fail
3	assertTrue(expr, msg=None)	验证expr是true，如果为false，则fail
4	assertFalse(expr,msg=None)	验证expr是false，如果为true，则fail
5	assertIs(arg1, arg2, msg=None)	验证arg1、arg2是同一个对象，不是则fail
6	assertIsNot(arg1, arg2, msg=None)	验证arg1、arg2不是同一个对象，是则fail
7	assertIsNone(expr, msg=None)	验证expr是None，不是则fail
8	assertIsNotNone(expr, msg=None)	验证expr不是None，是则fail
9	assertIn(arg1, arg2, msg=None)	验证arg1是arg2的子串，不是则fail
10	assertNotIn(arg1, arg2, msg=None)	验证arg1不是arg2的子串，是则fail
11	assertIsInstance(obj, cls, msg=None)	验证obj是cls的实例，不是则fail
12	assertNotIsInstance(obj, cls, msg=None)	验证obj不是cls的实例，是则fail

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)
|      Just like self.assertTrue(a in b), but with a nicer default message.
|
| assertIs(self, expr1, expr2, msg=None)
|      Just like self.assertTrue(a is b), but with a nicer default message.
|
| assertIsInstance(self, obj, cls, msg=None)
|      Same as self.assertTrue(isinstance(obj, cls)), with a nicer
|      default message.
|
| assertIsNone(self, obj, msg=None)
|      Same as self.assertTrue(obj is None), with a nicer default message.
|
| assertIsNot(self, expr1, expr2, msg=None)
|      Just like self.assertTrue(a is not b), but with a nicer default message.
|
| assertIsNotNone(self, obj, msg=None)
|      Included for symmetry with assertIsNone.
|
| assertItemsEqual(self, expected_seq, actual_seq, msg=None)
|      An unordered sequence specific comparison. It asserts that
|      actual_seq and expected_seq have the same element counts.
|      Equivalent to::
|
|          self.assertEqual(Counter(iter(actual_seq)),
|                           Counter(iter(expected_seq)))
|
|      Asserts that each element has the same count in both sequences.
|      Example:
|          - [0, 1, 1] and [1, 0, 1] compare equal.
|          - [0, 0, 1] and [0, 1] compare unequal.
|
| assertLess(self, a, b, msg=None)
|      Just like self.assertTrue(a < b), but with a nicer default message.
|
| assertLessEqual(self, a, b, msg=None)
|      Just like self.assertTrue(a <= b), but with a nicer default message.
|
| assertListEqual(self, list1, list2, msg=None)
|      A list-specific equality assertion.
|
|      Args:
|          list1: The first list to compare.
|          list2: The second list to compare.
|          msg: Optional message to use on failure instead of a list of
|                  differences.
|
| assertMultiLineEqual(self, first, second, msg=None)
|      Assert that two multi-line strings are equal.
|
| assertNotAlmostEqual(self, first, second, places=None, msg=None, delta=None)
|      Fail if the two objects are equal 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 less than the given delta.
|
|      Note that decimal places (from zero) are usually not the same
|      as significant digits (measured from the most signficant digit).
|
|      Objects that are equal automatically fail.
|
| assertNotAlmostEquals = assertNotAlmostEqual(self, first, second, places=None, msg=None, delta=None)
|
| assertNotEqual(self, first, second, msg=None)
|      Fail if the two objects are equal as determined by the '!='
|      operator.
|
| assertNotEquals = assertNotEqual(self, first, second, msg=None)
|
| assertNotIn(self, member, container, msg=None)
|      Just like self.assertTrue(a not in b), but with a nicer default message.
|
| assertNotIsInstance(self, obj, cls, msg=None)
|      Included for symmetry with assertIsInstance.
|
| assertNotRegexpMatches(self, text, unexpected_regexp, msg=None)
|      Fail the test if the text matches the regular expression.
|
| assertRaises(self, excClass, callableObj=None, *args, **kwargs)
|      Fail unless an exception of class excClass is raised
|      by callableObj when invoked with arguments args and keyword
|      arguments kwargs. If a different type of exception is
|      raised, it will not be caught, and the test case will be
|      deemed to have suffered an error, exactly as for an
|      unexpected exception.
|
|      If called with callableObj omitted or None, will return a
|      context object used like this::
|
|           with self.assertRaises(SomeException):
|               do_something()
|
|      The context manager keeps a reference to the exception as
|      the 'exception' attribute. This allows you to inspect the
|      exception after the assertion::
|
|          with self.assertRaises(SomeException) as cm:
|              do_something()
|          the_exception = cm.exception
|          self.assertEqual(the_exception.error_code, 3)
|
| assertRaisesRegexp(self, expected_exception, expected_regexp, callable_obj=None, *args, **kwargs)
|      Asserts that the message in a raised exception matches a regexp.
|
|      Args:
|          expected_exception: Exception class expected to be raised.
|          expected_regexp: Regexp (re pattern object or string) expected
|                  to be found in error message.
|          callable_obj: Function to be called.
|          args: Extra args.
|          kwargs: Extra kwargs.
|
| assertRegexpMatches(self, text, expected_regexp, msg=None)
|      Fail the test unless the text matches the regular expression.
|
| assertSequenceEqual(self, seq1, seq2, msg=None, seq_type=None)
|      An equality assertion for ordered sequences (like lists and tuples).
|
|      For the purposes of this function, a valid ordered sequence type is one
|      which can be indexed, has a length, and has an equality operator.
|
|      Args:
|          seq1: The first sequence to compare.
|          seq2: The second sequence to compare.
|          seq_type: The expected datatype of the sequences, or None if no
|                  datatype should be enforced.
|          msg: Optional message to use on failure instead of a list of
|                  differences.
|
| assertSetEqual(self, set1, set2, msg=None)
|      A set-specific equality assertion.
|
|      Args:
|          set1: The first set to compare.
|          set2: The second set to compare.
|          msg: Optional message to use on failure instead of a list of
|                  differences.
|
|      assertSetEqual uses ducktyping to support different types of sets, and
|      is optimized for sets specifically (parameters must support a
|      difference method).
|
| assertTrue(self, expr, msg=None)
|      Check that the expression is true.
|
| assertTupleEqual(self, tuple1, tuple2, msg=None)
|      A tuple-specific equality assertion.
|
|      Args:
|          tuple1: The first tuple to compare.
|          tuple2: The second tuple to compare.
|          msg: Optional message to use on failure instead of a list of
|                  differences.

转：https://www.cnblogs.com/yoyoketang/p/6691270.html

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基本断言方法

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