26.4. "unittest" --- 单元测试框架
*********************************

**源代码：** Lib/unittest/__init__.py

======================================================================

（如果你已经对测试的概念比较熟悉了，你可能想直接跳转到这一部分 断言方
法。）

"unittest" 单元测试框架是受到 JUnit 的启发，与其他语言中的主流单元测试
框架有着相似的风格。其支持测试自动化，配置共享和关机代码测试。支持将测
试样例聚合到测试集中，并将测试与报告框架独立。

为了实现这些，"unittest" 通过面向对象的方式支持了一些重要的概念。

测试脚手架
   *test fixture* 表示为了开展一项或多项测试所需要进行的准备工作，以及
   所有相关的清理操作。举个例子，这可能包含创建临时或代理的数据库、目
   录，再或者启动一个服务器进程。

测试用例
   一个测试用例是一个独立的测试单元。它检查输入特定的数据时的响应。
   "unittest" 提供一个基类： "TestCase" ，用于新建测试用例。

测试套件
   *test suite* 是一系列的测试用例，或测试套件，或两者皆有。它用于归档
   需要一起执行的测试。

测试运行器（test runner）
   *test runner* 是一个用于执行和输出测试结果的组件。这个运行器可能使
   用图形接口、文本接口，或返回一个特定的值表示运行测试的结果。

参见:

  "doctest" --- 文档测试模块
     另一个风格完全不同的测试模块。

  简单 Smalltalk 测试：便用模式
     Kent Beck 有关使用 "unittest" 所共享的模式的测试框架的原创论文。

  Nose and pytest
     Third-party unittest frameworks with a lighter-weight syntax for
     writing tests.  For example, "assert func(10) == 42".

  Python 测试工具分类
     一个 Python 测试工具的详细列表，包含测试框架和模拟对象库。

  Python 中的测试 邮件列表
     一个讨论 Python 中的测试和测试工具的特别兴趣小组。

  包含在源代码分发中的 "Tools/unittestgui/unittestgui.py" 文件是一个用
  于显示测试覆盖率和执行情况的 GUI 工具。它的目的是给那些单元测试的新
  手们提供方便。在生产环境中建议测试应由持续集成系统（continuous
  integration system）驱动，例如：Buildbot、 Jenkins 或 Hudson。


26.4.1. 基本实例
================

"unittest" 模块提供了一系列创建和运行测试的工具。这一段落演示了这些工
具的一小部分，但也足以满足大部分用户的需求。

这是一段简短的代码，来测试三种字符串方法:

   import unittest

   class TestStringMethods(unittest.TestCase):

       def test_upper(self):
           self.assertEqual('foo'.upper(), 'FOO')

       def test_isupper(self):
           self.assertTrue('FOO'.isupper())
           self.assertFalse('Foo'.isupper())

       def test_split(self):
           s = 'hello world'
           self.assertEqual(s.split(), ['hello', 'world'])
           # check that s.split fails when the separator is not a string
           with self.assertRaises(TypeError):
               s.split(2)

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

继承 "unittest.TestCase" 就创建了一个测试样例。上述三个独立的测试是三
个类的方法，这些方法的命名都以 "test" 开头。 这个命名约定告诉测试运行
者类的哪些方法表示测试。

每个测试的关键是：调用 "assertEqual()" 来检查预期的输出； 调用
"assertTrue()" 或 "assertFalse()" 来验证一个条件；调用
"assertRaises()" 来验证抛出了一个特定的异常。使用这些方法而不是
"assert" 语句是为了让测试运行者能聚合所有的测试结果并产生结果报告。

通过 "setUp()" 和 "tearDown()" 方法，可以设置测试开始前与完成后需要执
行的指令。 在  组织你的测试代码 中，对此有更为详细的描述。

最后的代码块中，演示了运行测试的一个简单的方法。 "unittest.main()" 提
供了一个测试脚本的命令行接口。当在命令行运行该测试脚本，上文的脚本生成
如以下格式的输出:

   ...
   ----------------------------------------------------------------------
   Ran 3 tests in 0.000s

   OK

在调用测试脚本时添加 "-v" 参数使 "unittest.main()" 显示更为详细的信息
，生成如以下形式的输出:

   test_isupper (__main__.TestStringMethods) ... ok
   test_split (__main__.TestStringMethods) ... ok
   test_upper (__main__.TestStringMethods) ... ok

   ----------------------------------------------------------------------
   Ran 3 tests in 0.001s

   OK

以上例子演示了 "unittest" 中最常用的、足够满足许多日常测试需求的特性。
文档的剩余部分详述该框架的完整特性。


26.4.2. 命令行界面
==================

unittest 模块可以通过命令行运行模块、类和独立测试方法的测试:

   python -m unittest test_module1 test_module2
   python -m unittest test_module.TestClass
   python -m unittest test_module.TestClass.test_method

你可以传入模块名、类或方法名或他们的任意组合。

同样的，测试模块可以通过文件路径指定:

   python -m unittest tests/test_something.py

这样就可以使用 shell 的文件名补全指定测试模块。所指定的文件仍需要可以
被作为模块导入。路径通过去除 '.py' 、把分隔符转换为 '.' 转换为模块名。
若你需要执行不能被作为模块导入的测试文件，你需要直接执行该测试文件。

在运行测试时，你可以通过添加 -v 参数获取更详细（更多的冗余）的信息。

   python -m unittest -v test_module

当运行时不包含参数，开始 探索性测试

   python -m unittest

用于获取命令行选项列表：

   python -m unittest -h

在 3.2 版更改: 在早期版本中，只支持运行独立的测试方法，而不支持模块和
类。


26.4.2.1. 命令行选项
--------------------

**unittest** supports these command-line options:

-b, --buffer

   在测试运行时，标准输出流与标准错误流会被放入缓冲区。成功的测试的运
   行时输出会被丢弃；测试不通过时，测试运行中的输出会正常显示，错误会
   被加入到测试失败信息。

-c, --catch

   当测试正在运行时， "Control-C" 会等待当前测试完成，并在完成后报告已
   执行的测试的结果。当再次按下 "Control-C" 时，引发平常的
   "KeyboardInterrupt" 异常。

   See Signal Handling for the functions that provide this
   functionality.

-f, --failfast

   当出现第一个错误或者失败时，停止运行测试。

--locals

   在回溯中显示局部变量。

3.2 新版功能: 添加命令行选项 "-b", "-c" 和 "-f" 。

3.5 新版功能: 命令行选项 "--locals" 。

命令行亦可用于探索性测试，以运行一个项目的所有测试或其子集。


26.4.3. 探索性测试
==================

3.2 新版功能.

Unittest支持简单的测试搜索。若需要使用探索性测试，所有的测试文件必须是
modules 或 packages （包括 *namespace packages* )并可从项目根目录导入
（即它们的文件名必须是有效的 identifiers ）。

探索性测试在 "TestLoader.discover()" 中实现，但也可以通过命令行使用。
它在命令行中的基本用法如下：

   cd project_directory
   python -m unittest discover

注解:

  方便起见， "python -m unittest" 与 "python -m unittest discover" 等
  价。如果你需要向探索性测试传入参数，必须显式地使用 "discover" 子命令
  。

"discover" 有以下选项：

-v, --verbose

   更详细地输出结果。

-s, --start-directory directory

   开始进行搜索的目录(默认值为当前目录 "." )。

-p, --pattern pattern

   用于匹配测试文件的模式（默认为 "test*.py" ）。

-t, --top-level-directory directory

   指定项目的最上层目录（通常为开始时所在目录）。

"-s" ，"-p" 和 "-t" 选项可以按顺序作为位置参数传入。以下两条命令是等价
的：

   python -m unittest discover -s project_directory -p "*_test.py"
   python -m unittest discover project_directory "*_test.py"

正如可以传入路径那样，传入一个包名作为起始目录也是可行的，如
"myproject.subpackage.test" 。你提供的包名会被导入，它在文件系统中的位
置会被作为起始目录。

警告:

  探索性测试通过导入测试对测试进行加载。在找到所有你指定的开始目录下的
  所有测试文件后，它把路径转换为包名并进行导入。如 "foo/bar/baz.py" 会
  被导入为 "foo.bar.baz" 。如果你有一个全局安装的包，并尝试对这个包的
  副本进行探索性测试，可能会从错误的地方开始导入。如果出现这种情况，测
  试会输出警告并退出。如果你使用包名而不是路径作为开始目录，搜索时会假
  定它导入的是你想要的目录，所以你不会收到警告。

测试模块和包可以通过 load_tests protocol 自定义测试的加载和搜索。

在 3.4 版更改: 探索性测试支持命名空间包（ *namespace packages* ）。


26.4.4. 组织你的测试代码
========================

单元测试的构建单位是 *test cases* ：独立的、包含执行条件与正确性检查的
方案。在 "unittest" 中，测试用例表示为 "unittest.TestCase" 的实例。通
过编写 "TestCase" 的子类或使用 "FunctionTestCase" 编写你自己的测试用例
。

一个 "TestCase" 实例的测试代码必须是完全自含的，因此它可以独立运行，或
与其它任意组合任意数量的测试用例一起运行。

"TestCase" 的最简单的子类需要实现一个测试方法（例如一个命名以 "test"
开头的方法）以执行特定的测试代码：

   import unittest

   class DefaultWidgetSizeTestCase(unittest.TestCase):
       def test_default_widget_size(self):
           widget = Widget('The widget')
           self.assertEqual(widget.size(), (50, 50))

可以看到，为了进行测试，我们使用了基类 "TestCase" 提供的其中一个
"assert*()" 方法。若测试不通过，将会引发一个带有说明信息的异常，并且
"unittest" 会将这个测试用例标记为测试不通过。任何其它类型的异常将会被
当做错误处理。

可能同时存在多个前置操作相同的测试，我们可以把测试的前置操作从测试代码
中拆解出来，并实现测试前置方法 "setUp()" 。在运行测试时，测试框架会自
动地为每个单独测试调用前置方法。

   import unittest

   class WidgetTestCase(unittest.TestCase):
       def setUp(self):
           self.widget = Widget('The widget')

       def test_default_widget_size(self):
           self.assertEqual(self.widget.size(), (50,50),
                            'incorrect default size')

       def test_widget_resize(self):
           self.widget.resize(100,150)
           self.assertEqual(self.widget.size(), (100,150),
                            'wrong size after resize')

注解:

  多个测试运行的顺序由内置字符串排序方法对测试名进行排序的结果决定。

在测试运行时，若 "setUp()" 方法引发异常，测试框架会认为测试发生了错误
，因此测试方法不会被运行。

相似的，我们提供了一个 "tearDown()" 方法在测试方法运行后进行清理工作。

   import unittest

   class WidgetTestCase(unittest.TestCase):
       def setUp(self):
           self.widget = Widget('The widget')

       def tearDown(self):
           self.widget.dispose()

若 "setUp()" 成功运行，无论测试方法是否成功，都会运行 "tearDown()" 。

这样的一个测试代码运行的环境被称为 *test fixture* 。一个新的 TestCase
实例作为一个测试脚手架，用于运行各个独立的测试方法。在运行每个测试时，
"setUp()" 、"tearDown()" 和 "__init__()" 会被调用一次。

建议你根据所测试的功能，将测试用 TestCase 实现集合起来。"unittest" 为
此提供了机制：*test suite*，以 "unittest" 的类 "TestSuite" 为代表。大
部分情况下，调用 "unittest.main()" 即可，并且它会为你集合所有模块的测
试用例并执行。

然而，如果你需要自定义你的测试套件的话，你可以参考以下方法组织你的测试
：

   def suite():
       suite = unittest.TestSuite()
       suite.addTest(WidgetTestCase('test_default_widget_size'))
       suite.addTest(WidgetTestCase('test_widget_resize'))
       return suite

   if __name__ == '__main__':
       runner = unittest.TextTestRunner()
       runner.run(suite())

你可以把测试用例和测试套件放在与被测试代码相同的模块中（比如
"widget.py"），但将测试代码放在单独的模块中（比如 "test_widget.py"）有
几个优势。

* 测试模块可以从命令行被独立调用。

* 更容易在分发的代码中剥离测试代码。

* 降低没有好理由的情况下修改测试代码以通过测试的诱惑。

* 测试代码应比被测试代码更少地被修改。

* 被测试代码可以更容易地被重构。

* 对用 C 语言写成的模块无论如何都得单独写成一个模块，为什么不保持一致
  呢？

* 如果测试策略发生了改变，没有必要修改源代码。


26.4.5. 复用已有的测试代码
==========================

一些用户希望直接使用 "unittest" 运行已有的测试代码，而不需要把已有的每
个测试函数转化为一个 "TestCase" 的子类。

因此， "unittest" 提供 "FunctionTestCase" 类。这个 "TestCase" 的子类可
用于打包已有的测试函数，并支持设置前置与后置函数。

假定有一个测试函数：

   def testSomething():
       something = makeSomething()
       assert something.name is not None
       # ...

可以创建等价的测试用例如下，其中前置和后置方法是可选的。

   testcase = unittest.FunctionTestCase(testSomething,
                                        setUp=makeSomethingDB,
                                        tearDown=deleteSomethingDB)

注解:

  可以用 "FunctionTestCase" 快速将现有的测试转换成基于 "unittest" 的测
  试，但不推荐。花点时间继承 "TestCase" 会让以后重构测试无比轻松。

In some cases, the existing tests may have been written using the
"doctest" module.  If so, "doctest" provides a "DocTestSuite" class
that can automatically build "unittest.TestSuite" instances from the
existing "doctest"-based tests.


26.4.6. 跳过测试与预计的失败
============================

3.1 新版功能.

Unittest 支持跳过单个或整组的测试用例。它还支持把测试标注成“预期失败”
的测试。这些坏测试会失败，但不会算进 "TestResult" 的失败里。

Skipping a test is simply a matter of using the "skip()" *decorator*
or one of its conditional variants.

跳过测试的基本用法如下:

   class MyTestCase(unittest.TestCase):

       @unittest.skip("demonstrating skipping")
       def test_nothing(self):
           self.fail("shouldn't happen")

       @unittest.skipIf(mylib.__version__ < (1, 3),
                        "not supported in this library version")
       def test_format(self):
           # Tests that work for only a certain version of the library.
           pass

       @unittest.skipUnless(sys.platform.startswith("win"), "requires Windows")
       def test_windows_support(self):
           # windows specific testing code
           pass

在啰嗦模式下运行以上测试例子时，程序输出如下：

   test_format (__main__.MyTestCase) ... skipped 'not supported in this library version'
   test_nothing (__main__.MyTestCase) ... skipped 'demonstrating skipping'
   test_windows_support (__main__.MyTestCase) ... skipped 'requires Windows'

   ----------------------------------------------------------------------
   Ran 3 tests in 0.005s

   OK (skipped=3)

跳过测试类的写法跟跳过测试方法的写法相似:

   @unittest.skip("showing class skipping")
   class MySkippedTestCase(unittest.TestCase):
       def test_not_run(self):
           pass

"TestCase.setUp()"  也可以跳过测试。可以用于所需资源不可用的情况下跳过
接下来的测试。

使用 "expectedFailure()" 装饰器表明这个测试预计失败。:

   class ExpectedFailureTestCase(unittest.TestCase):
       @unittest.expectedFailure
       def test_fail(self):
           self.assertEqual(1, 0, "broken")

It's easy to roll your own skipping decorators by making a decorator
that calls "skip()" on the test when it wants it to be skipped.  This
decorator skips the test unless the passed object has a certain
attribute:

   def skipUnlessHasattr(obj, attr):
       if hasattr(obj, attr):
           return lambda func: func
       return unittest.skip("{!r} doesn't have {!r}".format(obj, attr))

The following decorators implement test skipping and expected
failures:

@unittest.skip(reason)

   跳过被此装饰器装饰的测试。 *reason*  为测试被跳过的原因。

@unittest.skipIf(condition, reason)

   当 *condition* 为真时，跳过被装饰的测试。

@unittest.skipUnless(condition, reason)

   跳过被装饰的测试，除非 *condition* 为真。

@unittest.expectedFailure

   Mark the test as an expected failure.  If the test fails when run,
   the test is not counted as a failure.

exception unittest.SkipTest(reason)

   引发此异常以跳过一个测试。

   通常来说，你可以使用 "TestCase.skipTest()" 或其中一个跳过测试的装饰
   器实现跳过测试的功能，而不是直接引发此异常。

被跳过的测试的 "setUp()"  和 "tearDown()" 不会被运行。被跳过的类的
"setUpClass()" 和 "tearDownClass()" 不会被运行。被跳过的模组的
"setUpModule()" 和 "tearDownModule()" 不会被运行。


26.4.7. Distinguishing test iterations using subtests
=====================================================

3.4 新版功能.

When there are very small differences among your tests, for instance
some parameters, unittest allows you to distinguish them inside the
body of a test method using the "subTest()" context manager.

例如，以下测试:

   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)

可以得到以下输出:

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

   ======================================================================
   FAIL: test_even (__main__.NumbersTest) (i=3)
   ----------------------------------------------------------------------
   Traceback (most recent call last):
     File "subtests.py", line 32, in test_even
       self.assertEqual(i % 2, 0)
   AssertionError: 1 != 0

   ======================================================================
   FAIL: test_even (__main__.NumbersTest) (i=5)
   ----------------------------------------------------------------------
   Traceback (most recent call last):
     File "subtests.py", line 32, in test_even
       self.assertEqual(i % 2, 0)
   AssertionError: 1 != 0

如果不使用子测试，程序遇到第一次错误之后就会停止。而且因为``i``的值不
显示，错误也更难找。

   ======================================================================
   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


26.4.8. 类与函数
================

本节深入介绍了 "unittest" 的 API。


26.4.8.1. 测试用例
------------------

class unittest.TestCase(methodName='runTest')

   Instances of the "TestCase" class represent the logical test units
   in the "unittest" universe.  This class is intended to be used as a
   base class, with specific tests being implemented by concrete
   subclasses.  This class implements the interface needed by the test
   runner to allow it to drive the tests, and methods that the test
   code can use to check for and report various kinds of failure.

   Each instance of "TestCase" will run a single base method: the
   method named *methodName*. In most uses of "TestCase", you will
   neither change the *methodName* nor reimplement the default
   "runTest()" method.

   在 3.2 版更改: "TestCase" can be instantiated successfully without
   providing a *methodName*. This makes it easier to experiment with
   "TestCase" from the interactive interpreter.

   "TestCase" instances provide three groups of methods: one group
   used to run the test, another used by the test implementation to
   check conditions and report failures, and some inquiry methods
   allowing information about the test itself to be gathered.

   第一组（用于运行测试的）方法是：

   setUp()

      Method called to prepare the test fixture.  This is called
      immediately before calling the test method; other than
      "AssertionError" or "SkipTest", any exception raised by this
      method will be considered an error rather than a test failure.
      The default implementation does nothing.

   tearDown()

      Method called immediately after the test method has been called
      and the result recorded.  This is called even if the test method
      raised an exception, so the implementation in subclasses may
      need to be particularly careful about checking internal state.
      Any exception, other than "AssertionError" or "SkipTest", raised
      by this method will be considered an additional error rather
      than a test failure (thus increasing the total number of
      reported errors). This method will only be called if the
      "setUp()" succeeds, regardless of the outcome of the test
      method. The default implementation does nothing.

   setUpClass()

      A class method called before tests in an individual class are
      run. "setUpClass" is called with the class as the only argument
      and must be decorated as a "classmethod()":

         @classmethod
         def setUpClass(cls):
             ...

      查看 Class and Module Fixtures 获取更详细的说明。

      3.2 新版功能.

   tearDownClass()

      A class method called after tests in an individual class have
      run. "tearDownClass" is called with the class as the only
      argument and must be decorated as a "classmethod()":

         @classmethod
         def tearDownClass(cls):
             ...

      查看 Class and Module Fixtures 获取更详细的说明。

      3.2 新版功能.

   run(result=None)

      Run the test, collecting the result into the "TestResult" object
      passed as *result*.  If *result* is omitted or "None", a
      temporary result object is created (by calling the
      "defaultTestResult()" method) and used. The result object is
      returned to "run()"'s caller.

      The same effect may be had by simply calling the "TestCase"
      instance.

      在 3.3 版更改: Previous versions of "run" did not return the
      result. Neither did calling an instance.

   skipTest(reason)

      Calling this during a test method or "setUp()" skips the current
      test.  See 跳过测试与预计的失败 for more information.

      3.1 新版功能.

   subTest(msg=None, **params)

      Return a context manager which executes the enclosed code block
      as a subtest.  *msg* and *params* are optional, arbitrary values
      which are displayed whenever a subtest fails, allowing you to
      identify them clearly.

      A test case can contain any number of subtest declarations, and
      they can be arbitrarily nested.

      查看 Distinguishing test iterations using subtests 获取更详细的
      信息。

      3.4 新版功能.

   debug()

      Run the test without collecting the result.  This allows
      exceptions raised by the test to be propagated to the caller,
      and can be used to support running tests under a debugger.

   The "TestCase" class provides several assert methods to check for
   and report failures.  The following table lists the most commonly
   used methods (see the tables below for more assert methods):

   +-------------------------------------------+-------------------------------+-----------------+
   | Method                                    | Checks that                   | New in          |
   |===========================================|===============================|=================|
   | "assertEqual(a, b)"                       | "a == b"                      |                 |
   +-------------------------------------------+-------------------------------+-----------------+
   | "assertNotEqual(a, b)"                    | "a != b"                      |                 |
   +-------------------------------------------+-------------------------------+-----------------+
   | "assertTrue(x)"                           | "bool(x) is True"             |                 |
   +-------------------------------------------+-------------------------------+-----------------+
   | "assertFalse(x)"                          | "bool(x) is False"            |                 |
   +-------------------------------------------+-------------------------------+-----------------+
   | "assertIs(a, b)"                          | "a is b"                      | 3.1             |
   +-------------------------------------------+-------------------------------+-----------------+
   | "assertIsNot(a, b)"                       | "a is not b"                  | 3.1             |
   +-------------------------------------------+-------------------------------+-----------------+
   | "assertIsNone(x)"                         | "x is None"                   | 3.1             |
   +-------------------------------------------+-------------------------------+-----------------+
   | "assertIsNotNone(x)"                      | "x is not None"               | 3.1             |
   +-------------------------------------------+-------------------------------+-----------------+
   | "assertIn(a, b)"                          | "a in b"                      | 3.1             |
   +-------------------------------------------+-------------------------------+-----------------+
   | "assertNotIn(a, b)"                       | "a not in b"                  | 3.1             |
   +-------------------------------------------+-------------------------------+-----------------+
   | "assertIsInstance(a, b)"                  | "isinstance(a, b)"            | 3.2             |
   +-------------------------------------------+-------------------------------+-----------------+
   | "assertNotIsInstance(a, b)"               | "not isinstance(a, b)"        | 3.2             |
   +-------------------------------------------+-------------------------------+-----------------+

   All the assert methods accept a *msg* argument that, if specified,
   is used as the error message on failure (see also "longMessage").
   Note that the *msg* keyword argument can be passed to
   "assertRaises()", "assertRaisesRegex()", "assertWarns()",
   "assertWarnsRegex()" only when they are used as a context manager.

   assertEqual(first, second, msg=None)

      Test that *first* and *second* are equal.  If the values do not
      compare equal, the test will fail.

      In addition, if *first* and *second* are the exact same type and
      one of list, tuple, dict, set, frozenset or str or any type that
      a subclass registers with "addTypeEqualityFunc()" the type-
      specific equality function will be called in order to generate a
      more useful default error message (see also the list of type-
      specific methods).

      在 3.1 版更改: Added the automatic calling of type-specific
      equality function.

      在 3.2 版更改: "assertMultiLineEqual()" added as the default
      type equality function for comparing strings.

   assertNotEqual(first, second, msg=None)

      Test that *first* and *second* are not equal.  If the values do
      compare equal, the test will fail.

   assertTrue(expr, msg=None)
   assertFalse(expr, msg=None)

      Test that *expr* is true (or false).

      Note that this is equivalent to "bool(expr) is True" and not to
      "expr is True" (use "assertIs(expr, True)" for the latter).
      This method should also be avoided when more specific methods
      are available (e.g. "assertEqual(a, b)" instead of "assertTrue(a
      == b)"), because they provide a better error message in case of
      failure.

   assertIs(first, second, msg=None)
   assertIsNot(first, second, msg=None)

      Test that *first* and *second* evaluate (or don't evaluate) to
      the same object.

      3.1 新版功能.

   assertIsNone(expr, msg=None)
   assertIsNotNone(expr, msg=None)

      Test that *expr* is (or is not) "None".

      3.1 新版功能.

   assertIn(first, second, msg=None)
   assertNotIn(first, second, msg=None)

      Test that *first* is (or is not) in *second*.

      3.1 新版功能.

   assertIsInstance(obj, cls, msg=None)
   assertNotIsInstance(obj, cls, msg=None)

      Test that *obj* is (or is not) an instance of *cls* (which can
      be a class or a tuple of classes, as supported by
      "isinstance()"). To check for the exact type, use
      "assertIs(type(obj), cls)".

      3.2 新版功能.

   It is also possible to check the production of exceptions,
   warnings, and log messages using the following methods:

   +-----------------------------------------------------------+----------------------------------------+--------------+
   | Method                                                    | Checks that                            | New in       |
   |===========================================================|========================================|==============|
   | "assertRaises(exc, fun, *args, **kwds)"                   | "fun(*args, **kwds)" raises *exc*      |              |
   +-----------------------------------------------------------+----------------------------------------+--------------+
   | "assertRaisesRegex(exc, r, fun, *args, **kwds)"           | "fun(*args, **kwds)" raises *exc* and  | 3.1          |
   |                                                           | the message matches regex *r*          |              |
   +-----------------------------------------------------------+----------------------------------------+--------------+
   | "assertWarns(warn, fun, *args, **kwds)"                   | "fun(*args, **kwds)" raises *warn*     | 3.2          |
   +-----------------------------------------------------------+----------------------------------------+--------------+
   | "assertWarnsRegex(warn, r, fun, *args, **kwds)"           | "fun(*args, **kwds)" raises *warn* and | 3.2          |
   |                                                           | the message matches regex *r*          |              |
   +-----------------------------------------------------------+----------------------------------------+--------------+
   | "assertLogs(logger, level)"                               | The "with" block logs on *logger* with | 3.4          |
   |                                                           | minimum *level*                        |              |
   +-----------------------------------------------------------+----------------------------------------+--------------+

   assertRaises(exception, callable, *args, **kwds)
   assertRaises(exception, *, msg=None)

      Test that an exception is raised when *callable* is called with
      any positional or keyword arguments that are also passed to
      "assertRaises()".  The test passes if *exception* is raised, is
      an error if another exception is raised, or fails if no
      exception is raised. To catch any of a group of exceptions, a
      tuple containing the exception classes may be passed as
      *exception*.

      If only the *exception* and possibly the *msg* arguments are
      given, return a context manager so that the code under test can
      be written inline rather than as a function:

         with self.assertRaises(SomeException):
             do_something()

      When used as a context manager, "assertRaises()" accepts the
      additional keyword argument *msg*.

      The context manager will store the caught exception object in
      its "exception" attribute.  This can be useful if the intention
      is to perform additional checks on the exception raised:

         with self.assertRaises(SomeException) as cm:
             do_something()

         the_exception = cm.exception
         self.assertEqual(the_exception.error_code, 3)

      在 3.1 版更改: Added the ability to use "assertRaises()" as a
      context manager.

      在 3.2 版更改: Added the "exception" attribute.

      在 3.3 版更改: Added the *msg* keyword argument when used as a
      context manager.

   assertRaisesRegex(exception, regex, callable, *args, **kwds)
   assertRaisesRegex(exception, regex, *, msg=None)

      Like "assertRaises()" but also tests that *regex* matches on the
      string representation of the raised exception.  *regex* may be a
      regular expression object or a string containing a regular
      expression suitable for use by "re.search()".  Examples:

         self.assertRaisesRegex(ValueError, "invalid literal for.*XYZ'$",
                                int, 'XYZ')

      或者：

         with self.assertRaisesRegex(ValueError, 'literal'):
            int('XYZ')

      3.1 新版功能: under the name "assertRaisesRegexp".

      在 3.2 版更改: Renamed to "assertRaisesRegex()".

      在 3.3 版更改: Added the *msg* keyword argument when used as a
      context manager.

   assertWarns(warning, callable, *args, **kwds)
   assertWarns(warning, *, msg=None)

      Test that a warning is triggered when *callable* is called with
      any positional or keyword arguments that are also passed to
      "assertWarns()".  The test passes if *warning* is triggered and
      fails if it isn't.  Any exception is an error. To catch any of a
      group of warnings, a tuple containing the warning classes may be
      passed as *warnings*.

      If only the *warning* and possibly the *msg* arguments are
      given, return a context manager so that the code under test can
      be written inline rather than as a function:

         with self.assertWarns(SomeWarning):
             do_something()

      When used as a context manager, "assertWarns()" accepts the
      additional keyword argument *msg*.

      The context manager will store the caught warning object in its
      "warning" attribute, and the source line which triggered the
      warnings in the "filename" and "lineno" attributes. This can be
      useful if the intention is to perform additional checks on the
      warning caught:

         with self.assertWarns(SomeWarning) as cm:
             do_something()

         self.assertIn('myfile.py', cm.filename)
         self.assertEqual(320, cm.lineno)

      This method works regardless of the warning filters in place
      when it is called.

      3.2 新版功能.

      在 3.3 版更改: Added the *msg* keyword argument when used as a
      context manager.

   assertWarnsRegex(warning, regex, callable, *args, **kwds)
   assertWarnsRegex(warning, regex, *, msg=None)

      Like "assertWarns()" but also tests that *regex* matches on the
      message of the triggered warning.  *regex* may be a regular
      expression object or a string containing a regular expression
      suitable for use by "re.search()".  Example:

         self.assertWarnsRegex(DeprecationWarning,
                               r'legacy_function\(\) is deprecated',
                               legacy_function, 'XYZ')

      或者：

         with self.assertWarnsRegex(RuntimeWarning, 'unsafe frobnicating'):
             frobnicate('/etc/passwd')

      3.2 新版功能.

      在 3.3 版更改: Added the *msg* keyword argument when used as a
      context manager.

   assertLogs(logger=None, level=None)

      A context manager to test that at least one message is logged on
      the *logger* or one of its children, with at least the given
      *level*.

      If given, *logger* should be a "logging.Logger" object or a
      "str" giving the name of a logger.  The default is the root
      logger, which will catch all messages.

      If given, *level* should be either a numeric logging level or
      its string equivalent (for example either ""ERROR"" or
      "logging.ERROR").  The default is "logging.INFO".

      The test passes if at least one message emitted inside the
      "with" block matches the *logger* and *level* conditions,
      otherwise it fails.

      The object returned by the context manager is a recording helper
      which keeps tracks of the matching log messages.  It has two
      attributes:

      records

         A list of "logging.LogRecord" objects of the matching log
         messages.

      output

         A list of "str" objects with the formatted output of matching
         messages.

      示例:

         with self.assertLogs('foo', level='INFO') as cm:
            logging.getLogger('foo').info('first message')
            logging.getLogger('foo.bar').error('second message')
         self.assertEqual(cm.output, ['INFO:foo:first message',
                                      'ERROR:foo.bar:second message'])

      3.4 新版功能.

   There are also other methods used to perform more specific checks,
   such as:

   +-----------------------------------------+----------------------------------+----------------+
   | Method                                  | Checks that                      | New in         |
   |=========================================|==================================|================|
   | "assertAlmostEqual(a, b)"               | "round(a-b, 7) == 0"             |                |
   +-----------------------------------------+----------------------------------+----------------+
   | "assertNotAlmostEqual(a, b)"            | "round(a-b, 7) != 0"             |                |
   +-----------------------------------------+----------------------------------+----------------+
   | "assertGreater(a, b)"                   | "a > b"                          | 3.1            |
   +-----------------------------------------+----------------------------------+----------------+
   | "assertGreaterEqual(a, b)"              | "a >= b"                         | 3.1            |
   +-----------------------------------------+----------------------------------+----------------+
   | "assertLess(a, b)"                      | "a < b"                          | 3.1            |
   +-----------------------------------------+----------------------------------+----------------+
   | "assertLessEqual(a, b)"                 | "a <= b"                         | 3.1            |
   +-----------------------------------------+----------------------------------+----------------+
   | "assertRegex(s, r)"                     | "r.search(s)"                    | 3.1            |
   +-----------------------------------------+----------------------------------+----------------+
   | "assertNotRegex(s, r)"                  | "not r.search(s)"                | 3.2            |
   +-----------------------------------------+----------------------------------+----------------+
   | "assertCountEqual(a, b)"                | *a* and *b* have the same        | 3.2            |
   |                                         | elements in the same number,     |                |
   |                                         | regardless of their order        |                |
   +-----------------------------------------+----------------------------------+----------------+

   assertAlmostEqual(first, second, places=7, msg=None, delta=None)
   assertNotAlmostEqual(first, second, places=7, msg=None, delta=None)

      Test that *first* and *second* are approximately (or not
      approximately) equal by computing the difference, rounding to
      the given number of decimal *places* (default 7), and comparing
      to zero.  Note that these methods round the values to the given
      number of *decimal places* (i.e. like the "round()" function)
      and not *significant digits*.

      If *delta* is supplied instead of *places* then the difference
      between *first* and *second* must be less or equal to (or
      greater than) *delta*.

      Supplying both *delta* and *places* raises a "TypeError".

      在 3.2 版更改: "assertAlmostEqual()" automatically considers
      almost equal objects that compare equal.
      "assertNotAlmostEqual()" automatically fails if the objects
      compare equal.  Added the *delta* keyword argument.

   assertGreater(first, second, msg=None)
   assertGreaterEqual(first, second, msg=None)
   assertLess(first, second, msg=None)
   assertLessEqual(first, second, msg=None)

      Test that *first* is respectively >, >=, < or <= than *second*
      depending on the method name.  If not, the test will fail:

         >>> self.assertGreaterEqual(3, 4)
         AssertionError: "3" unexpectedly not greater than or equal to "4"

      3.1 新版功能.

   assertRegex(text, regex, msg=None)
   assertNotRegex(text, regex, msg=None)

      测试一个 *regex* 是否匹配 *文本*。如果不匹配，错误信息中将包含匹
      配模式和 *文本*（或部分匹配失败的 *文本*）。*regex* 可以是正则表
      达式对象或能够用于 "re.search()" 的包含正则表达式的字符串。

      3.1 新版功能: under the name "assertRegexpMatches".

      在 3.2 版更改: 方法 "assertRegexpMatches()" 已被改名为
      "assertRegex()"。

      3.2 新版功能: "assertNotRegex()"

      3.5 新版功能: "assertNotRegexpMatches" 这个名字是
      "assertNotRegex()" 的已被弃用的别名。

   assertCountEqual(first, second, msg=None)

      Test that sequence *first* contains the same elements as
      *second*, regardless of their order. When they don't, an error
      message listing the differences between the sequences will be
      generated.

      Duplicate elements are *not* ignored when comparing *first* and
      *second*. It verifies whether each element has the same count in
      both sequences. Equivalent to:
      "assertEqual(Counter(list(first)), Counter(list(second)))" but
      works with sequences of unhashable objects as well.

      3.2 新版功能.

   The "assertEqual()" method dispatches the equality check for
   objects of the same type to different type-specific methods.  These
   methods are already implemented for most of the built-in types, but
   it's also possible to register new methods using
   "addTypeEqualityFunc()":

   addTypeEqualityFunc(typeobj, function)

      Registers a type-specific method called by "assertEqual()" to
      check if two objects of exactly the same *typeobj* (not
      subclasses) compare equal.  *function* must take two positional
      arguments and a third msg=None keyword argument just as
      "assertEqual()" does.  It must raise
      "self.failureException(msg)" when inequality between the first
      two parameters is detected -- possibly providing useful
      information and explaining the inequalities in details in the
      error message.

      3.1 新版功能.

   以下是 "assertEqual()" 自动选用的不同类型的比较方法。一般情况下不需
   要直接在测试中调用这些方法。

   +-------------------------------------------+-------------------------------+----------------+
   | Method                                    | 用作比较                      | New in         |
   |===========================================|===============================|================|
   | "assertMultiLineEqual(a, b)"              | 字符串                        | 3.1            |
   +-------------------------------------------+-------------------------------+----------------+
   | "assertSequenceEqual(a, b)"               | 序列                          | 3.1            |
   +-------------------------------------------+-------------------------------+----------------+
   | "assertListEqual(a, b)"                   | 列表                          | 3.1            |
   +-------------------------------------------+-------------------------------+----------------+
   | "assertTupleEqual(a, b)"                  | 元组                          | 3.1            |
   +-------------------------------------------+-------------------------------+----------------+
   | "assertSetEqual(a, b)"                    | 集合                          | 3.1            |
   +-------------------------------------------+-------------------------------+----------------+
   | "assertDictEqual(a, b)"                   | 字典                          | 3.1            |
   +-------------------------------------------+-------------------------------+----------------+

   assertMultiLineEqual(first, second, msg=None)

      Test that the multiline string *first* is equal to the string
      *second*. When not equal a diff of the two strings highlighting
      the differences will be included in the error message. This
      method is used by default when comparing strings with
      "assertEqual()".

      3.1 新版功能.

   assertSequenceEqual(first, second, msg=None, seq_type=None)

      Tests that two sequences are equal.  If a *seq_type* is
      supplied, both *first* and *second* must be instances of
      *seq_type* or a failure will be raised.  If the sequences are
      different an error message is constructed that shows the
      difference between the two.

      This method is not called directly by "assertEqual()", but it's
      used to implement "assertListEqual()" and "assertTupleEqual()".

      3.1 新版功能.

   assertListEqual(first, second, msg=None)
   assertTupleEqual(first, second, msg=None)

      Tests that two lists or tuples are equal.  If not, an error
      message is constructed that shows only the differences between
      the two.  An error is also raised if either of the parameters
      are of the wrong type. These methods are used by default when
      comparing lists or tuples with "assertEqual()".

      3.1 新版功能.

   assertSetEqual(first, second, msg=None)

      Tests that two sets are equal.  If not, an error message is
      constructed that lists the differences between the sets.  This
      method is used by default when comparing sets or frozensets with
      "assertEqual()".

      Fails if either of *first* or *second* does not have a
      "set.difference()" method.

      3.1 新版功能.

   assertDictEqual(first, second, msg=None)

      Test that two dictionaries are equal.  If not, an error message
      is constructed that shows the differences in the dictionaries.
      This method will be used by default to compare dictionaries in
      calls to "assertEqual()".

      3.1 新版功能.

   Finally the "TestCase" provides the following methods and
   attributes:

   fail(msg=None)

      Signals a test failure unconditionally, with *msg* or "None" for
      the error message.

   failureException

      This class attribute gives the exception raised by the test
      method.  If a test framework needs to use a specialized
      exception, possibly to carry additional information, it must
      subclass this exception in order to "play fair" with the
      framework.  The initial value of this attribute is
      "AssertionError".

   longMessage

      This class attribute determines what happens when a custom
      failure message is passed as the msg argument to an assertXYY
      call that fails. "True" is the default value. In this case, the
      custom message is appended to the end of the standard failure
      message. When set to "False", the custom message replaces the
      standard message.

      The class setting can be overridden in individual test methods
      by assigning an instance attribute, self.longMessage, to "True"
      or "False" before calling the assert methods.

      The class setting gets reset before each test call.

      3.1 新版功能.

   maxDiff

      This attribute controls the maximum length of diffs output by
      assert methods that report diffs on failure. It defaults to 80*8
      characters. Assert methods affected by this attribute are
      "assertSequenceEqual()" (including all the sequence comparison
      methods that delegate to it), "assertDictEqual()" and
      "assertMultiLineEqual()".

      Setting "maxDiff" to "None" means that there is no maximum
      length of diffs.

      3.2 新版功能.

   Testing frameworks can use the following methods to collect
   information on the test:

   countTestCases()

      Return the number of tests represented by this test object.  For
      "TestCase" instances, this will always be "1".

   defaultTestResult()

      Return an instance of the test result class that should be used
      for this test case class (if no other result instance is
      provided to the "run()" method).

      For "TestCase" instances, this will always be an instance of
      "TestResult"; subclasses of "TestCase" should override this as
      necessary.

   id()

      Return a string identifying the specific test case.  This is
      usually the full name of the test method, including the module
      and class name.

   shortDescription()

      Returns a description of the test, or "None" if no description
      has been provided.  The default implementation of this method
      returns the first line of the test method's docstring, if
      available, or "None".

      在 3.1 版更改: In 3.1 this was changed to add the test name to
      the short description even in the presence of a docstring.  This
      caused compatibility issues with unittest extensions and adding
      the test name was moved to the "TextTestResult" in Python 3.2.

   addCleanup(function, *args, **kwargs)

      Add a function to be called after "tearDown()" to cleanup
      resources used during the test. Functions will be called in
      reverse order to the order they are added (LIFO (last-in, first-
      out)).  They are called with any arguments and keyword arguments
      passed into "addCleanup()" when they are added.

      If "setUp()" fails, meaning that "tearDown()" is not called,
      then any cleanup functions added will still be called.

      3.1 新版功能.

   doCleanups()

      This method is called unconditionally after "tearDown()", or
      after "setUp()" if "setUp()" raises an exception.

      It is responsible for calling all the cleanup functions added by
      "addCleanup()". If you need cleanup functions to be called
      *prior* to "tearDown()" then you can call "doCleanups()"
      yourself.

      "doCleanups()" pops methods off the stack of cleanup functions
      one at a time, so it can be called at any time.

      3.1 新版功能.

class unittest.FunctionTestCase(testFunc, setUp=None, tearDown=None, description=None)

   This class implements the portion of the "TestCase" interface which
   allows the test runner to drive the test, but does not provide the
   methods which test code can use to check and report errors.  This
   is used to create test cases using legacy test code, allowing it to
   be integrated into a "unittest"-based test framework.


26.4.8.1.1. Deprecated aliases
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

For historical reasons, some of the "TestCase" methods had one or more
aliases that are now deprecated.  The following table lists the
correct names along with their deprecated aliases:

   +--------------------------------+------------------------+-------------------------+
   | 方法名                         | Deprecated alias       | Deprecated alias        |
   |================================|========================|=========================|
   | "assertEqual()"                | failUnlessEqual        | assertEquals            |
   +--------------------------------+------------------------+-------------------------+
   | "assertNotEqual()"             | failIfEqual            | assertNotEquals         |
   +--------------------------------+------------------------+-------------------------+
   | "assertTrue()"                 | failUnless             | assert_                 |
   +--------------------------------+------------------------+-------------------------+
   | "assertFalse()"                | failIf                 |                         |
   +--------------------------------+------------------------+-------------------------+
   | "assertRaises()"               | failUnlessRaises       |                         |
   +--------------------------------+------------------------+-------------------------+
   | "assertAlmostEqual()"          | failUnlessAlmostEqual  | assertAlmostEquals      |
   +--------------------------------+------------------------+-------------------------+
   | "assertNotAlmostEqual()"       | failIfAlmostEqual      | assertNotAlmostEquals   |
   +--------------------------------+------------------------+-------------------------+
   | "assertRegex()"                |                        | assertRegexpMatches     |
   +--------------------------------+------------------------+-------------------------+
   | "assertNotRegex()"             |                        | assertNotRegexpMatches  |
   +--------------------------------+------------------------+-------------------------+
   | "assertRaisesRegex()"          |                        | assertRaisesRegexp      |
   +--------------------------------+------------------------+-------------------------+

   3.1 版后已移除: the fail* aliases listed in the second column.

   3.2 版后已移除: the assert* aliases listed in the third column.

   3.2 版后已移除: "assertRegexpMatches" and "assertRaisesRegexp" have
   been renamed to "assertRegex()" and "assertRaisesRegex()".

   3.5 版后已移除: the "assertNotRegexpMatches" name in favor of
   "assertNotRegex()".


26.4.8.2. Grouping tests
------------------------

class unittest.TestSuite(tests=())

   This class represents an aggregation of individual test cases and
   test suites. The class presents the interface needed by the test
   runner to allow it to be run as any other test case.  Running a
   "TestSuite" instance is the same as iterating over the suite,
   running each test individually.

   If *tests* is given, it must be an iterable of individual test
   cases or other test suites that will be used to build the suite
   initially. Additional methods are provided to add test cases and
   suites to the collection later on.

   "TestSuite" objects behave much like "TestCase" objects, except
   they do not actually implement a test.  Instead, they are used to
   aggregate tests into groups of tests that should be run together.
   Some additional methods are available to add tests to "TestSuite"
   instances:

   addTest(test)

      Add a "TestCase" or "TestSuite" to the suite.

   addTests(tests)

      Add all the tests from an iterable of "TestCase" and "TestSuite"
      instances to this test suite.

      This is equivalent to iterating over *tests*, calling
      "addTest()" for each element.

   "TestSuite" shares the following methods with "TestCase":

   run(result)

      Run the tests associated with this suite, collecting the result
      into the test result object passed as *result*.  Note that
      unlike "TestCase.run()", "TestSuite.run()" requires the result
      object to be passed in.

   debug()

      Run the tests associated with this suite without collecting the
      result. This allows exceptions raised by the test to be
      propagated to the caller and can be used to support running
      tests under a debugger.

   countTestCases()

      Return the number of tests represented by this test object,
      including all individual tests and sub-suites.

   __iter__()

      Tests grouped by a "TestSuite" are always accessed by iteration.
      Subclasses can lazily provide tests by overriding "__iter__()".
      Note that this method may be called several times on a single
      suite (for example when counting tests or comparing for
      equality) so the tests returned by repeated iterations before
      "TestSuite.run()" must be the same for each call iteration.
      After "TestSuite.run()", callers should not rely on the tests
      returned by this method unless the caller uses a subclass that
      overrides "TestSuite._removeTestAtIndex()" to preserve test
      references.

      在 3.2 版更改: In earlier versions the "TestSuite" accessed
      tests directly rather than through iteration, so overriding
      "__iter__()" wasn't sufficient for providing tests.

      在 3.4 版更改: In earlier versions the "TestSuite" held
      references to each "TestCase" after "TestSuite.run()".
      Subclasses can restore that behavior by overriding
      "TestSuite._removeTestAtIndex()".

   In the typical usage of a "TestSuite" object, the "run()" method is
   invoked by a "TestRunner" rather than by the end-user test harness.


26.4.8.3. Loading and running tests
-----------------------------------

class unittest.TestLoader

   The "TestLoader" class is used to create test suites from classes
   and modules.  Normally, there is no need to create an instance of
   this class; the "unittest" module provides an instance that can be
   shared as "unittest.defaultTestLoader".  Using a subclass or
   instance, however, allows customization of some configurable
   properties.

   "TestLoader" objects have the following attributes:

   errors

      A list of the non-fatal errors encountered while loading tests.
      Not reset by the loader at any point. Fatal errors are signalled
      by the relevant a method raising an exception to the caller.
      Non-fatal errors are also indicated by a synthetic test that
      will raise the original error when run.

      3.5 新版功能.

   "TestLoader" objects have the following methods:

   loadTestsFromTestCase(testCaseClass)

      Return a suite of all test cases contained in the
      "TestCase"-derived "testCaseClass".

      A test case instance is created for each method named by
      "getTestCaseNames()". By default these are the method names
      beginning with "test". If "getTestCaseNames()" returns no
      methods, but the "runTest()" method is implemented, a single
      test case is created for that method instead.

   loadTestsFromModule(module, pattern=None)

      Return a suite of all test cases contained in the given module.
      This method searches *module* for classes derived from
      "TestCase" and creates an instance of the class for each test
      method defined for the class.

      注解:

        While using a hierarchy of "TestCase"-derived classes can be
        convenient in sharing fixtures and helper functions, defining
        test methods on base classes that are not intended to be
        instantiated directly does not play well with this method.
        Doing so, however, can be useful when the fixtures are
        different and defined in subclasses.

      If a module provides a "load_tests" function it will be called
      to load the tests. This allows modules to customize test
      loading. This is the load_tests protocol.  The *pattern*
      argument is passed as the third argument to "load_tests".

      在 3.2 版更改: Support for "load_tests" added.

      在 3.5 版更改: The undocumented and unofficial *use_load_tests*
      default argument is deprecated and ignored, although it is still
      accepted for backward compatibility.  The method also now
      accepts a keyword-only argument *pattern* which is passed to
      "load_tests" as the third argument.

   loadTestsFromName(name, module=None)

      Return a suite of all test cases given a string specifier.

      The specifier *name* is a "dotted name" that may resolve either
      to a module, a test case class, a test method within a test case
      class, a "TestSuite" instance, or a callable object which
      returns a "TestCase" or "TestSuite" instance.  These checks are
      applied in the order listed here; that is, a method on a
      possible test case class will be picked up as "a test method
      within a test case class", rather than "a callable object".

      For example, if you have a module "SampleTests" containing a
      "TestCase"-derived class "SampleTestCase" with three test
      methods ("test_one()", "test_two()", and "test_three()"), the
      specifier "'SampleTests.SampleTestCase'" would cause this method
      to return a suite which will run all three test methods. Using
      the specifier "'SampleTests.SampleTestCase.test_two'" would
      cause it to return a test suite which will run only the
      "test_two()" test method. The specifier can refer to modules and
      packages which have not been imported; they will be imported as
      a side-effect.

      The method optionally resolves *name* relative to the given
      *module*.

      在 3.5 版更改: If an "ImportError" or "AttributeError" occurs
      while traversing *name* then a synthetic test that raises that
      error when run will be returned. These errors are included in
      the errors accumulated by self.errors.

   loadTestsFromNames(names, module=None)

      Similar to "loadTestsFromName()", but takes a sequence of names
      rather than a single name.  The return value is a test suite
      which supports all the tests defined for each name.

   getTestCaseNames(testCaseClass)

      Return a sorted sequence of method names found within
      *testCaseClass*; this should be a subclass of "TestCase".

   discover(start_dir, pattern='test*.py', top_level_dir=None)

      Find all the test modules by recursing into subdirectories from
      the specified start directory, and return a TestSuite object
      containing them. Only test files that match *pattern* will be
      loaded. (Using shell style pattern matching.) Only module names
      that are importable (i.e. are valid Python identifiers) will be
      loaded.

      All test modules must be importable from the top level of the
      project. If the start directory is not the top level directory
      then the top level directory must be specified separately.

      If importing a module fails, for example due to a syntax error,
      then this will be recorded as a single error and discovery will
      continue.  If the import failure is due to "SkipTest" being
      raised, it will be recorded as a skip instead of an error.

      If a package (a directory containing a file named "__init__.py")
      is found, the package will be checked for a "load_tests"
      function. If this exists then it will be called
      "package.load_tests(loader, tests, pattern)". Test discovery
      takes care to ensure that a package is only checked for tests
      once during an invocation, even if the load_tests function
      itself calls "loader.discover".

      If "load_tests" exists then discovery does *not* recurse into
      the package, "load_tests" is responsible for loading all tests
      in the package.

      The pattern is deliberately not stored as a loader attribute so
      that packages can continue discovery themselves. *top_level_dir*
      is stored so "load_tests" does not need to pass this argument in
      to "loader.discover()".

      *start_dir* can be a dotted module name as well as a directory.

      3.2 新版功能.

      在 3.4 版更改: Modules that raise "SkipTest" on import are
      recorded as skips,   not errors. Discovery works for *namespace
      packages*. Paths are sorted before being imported so that
      execution order is   the same even if the underlying file
      system's ordering is not   dependent on file name.

      在 3.5 版更改: Found packages are now checked for "load_tests"
      regardless of whether their path matches *pattern*, because it
      is impossible for a package name to match the default pattern.

   The following attributes of a "TestLoader" can be configured either
   by subclassing or assignment on an instance:

   testMethodPrefix

      String giving the prefix of method names which will be
      interpreted as test methods.  The default value is "'test'".

      This affects "getTestCaseNames()" and all the "loadTestsFrom*()"
      methods.

   sortTestMethodsUsing

      Function to be used to compare method names when sorting them in
      "getTestCaseNames()" and all the "loadTestsFrom*()" methods.

   suiteClass

      Callable object that constructs a test suite from a list of
      tests. No methods on the resulting object are needed.  The
      default value is the "TestSuite" class.

      This affects all the "loadTestsFrom*()" methods.

class unittest.TestResult

   This class is used to compile information about which tests have
   succeeded and which have failed.

   A "TestResult" object stores the results of a set of tests.  The
   "TestCase" and "TestSuite" classes ensure that results are properly
   recorded; test authors do not need to worry about recording the
   outcome of tests.

   Testing frameworks built on top of "unittest" may want access to
   the "TestResult" object generated by running a set of tests for
   reporting purposes; a "TestResult" instance is returned by the
   "TestRunner.run()" method for this purpose.

   "TestResult" instances have the following attributes that will be
   of interest when inspecting the results of running a set of tests:

   errors

      A list containing 2-tuples of "TestCase" instances and strings
      holding formatted tracebacks. Each tuple represents a test which
      raised an unexpected exception.

   failures

      A list containing 2-tuples of "TestCase" instances and strings
      holding formatted tracebacks. Each tuple represents a test where
      a failure was explicitly signalled using the
      "TestCase.assert*()" methods.

   skipped

      A list containing 2-tuples of "TestCase" instances and strings
      holding the reason for skipping the test.

      3.1 新版功能.

   expectedFailures

      A list containing 2-tuples of "TestCase" instances and strings
      holding formatted tracebacks.  Each tuple represents an expected
      failure of the test case.

   unexpectedSuccesses

      A list containing "TestCase" instances that were marked as
      expected failures, but succeeded.

   shouldStop

      Set to "True" when the execution of tests should stop by
      "stop()".

   testsRun

      The total number of tests run so far.

   buffer

      If set to true, "sys.stdout" and "sys.stderr" will be buffered
      in between "startTest()" and "stopTest()" being called.
      Collected output will only be echoed onto the real "sys.stdout"
      and "sys.stderr" if the test fails or errors. Any output is also
      attached to the failure / error message.

      3.2 新版功能.

   failfast

      If set to true "stop()" will be called on the first failure or
      error, halting the test run.

      3.2 新版功能.

   tb_locals

      If set to true then local variables will be shown in tracebacks.

      3.5 新版功能.

   wasSuccessful()

      Return "True" if all tests run so far have passed, otherwise
      returns "False".

      在 3.4 版更改: Returns "False" if there were any
      "unexpectedSuccesses" from tests marked with the
      "expectedFailure()" decorator.

   stop()

      This method can be called to signal that the set of tests being
      run should be aborted by setting the "shouldStop" attribute to
      "True". "TestRunner" objects should respect this flag and return
      without running any additional tests.

      For example, this feature is used by the "TextTestRunner" class
      to stop the test framework when the user signals an interrupt
      from the keyboard.  Interactive tools which provide "TestRunner"
      implementations can use this in a similar manner.

   The following methods of the "TestResult" class are used to
   maintain the internal data structures, and may be extended in
   subclasses to support additional reporting requirements.  This is
   particularly useful in building tools which support interactive
   reporting while tests are being run.

   startTest(test)

      Called when the test case *test* is about to be run.

   stopTest(test)

      Called after the test case *test* has been executed, regardless
      of the outcome.

   startTestRun()

      Called once before any tests are executed.

      3.1 新版功能.

   stopTestRun()

      Called once after all tests are executed.

      3.1 新版功能.

   addError(test, err)

      Called when the test case *test* raises an unexpected exception.
      *err* is a tuple of the form returned by "sys.exc_info()":
      "(type, value, traceback)".

      The default implementation appends a tuple "(test,
      formatted_err)" to the instance's "errors" attribute, where
      *formatted_err* is a formatted traceback derived from *err*.

   addFailure(test, err)

      Called when the test case *test* signals a failure. *err* is a
      tuple of the form returned by "sys.exc_info()": "(type, value,
      traceback)".

      The default implementation appends a tuple "(test,
      formatted_err)" to the instance's "failures" attribute, where
      *formatted_err* is a formatted traceback derived from *err*.

   addSuccess(test)

      Called when the test case *test* succeeds.

      The default implementation does nothing.

   addSkip(test, reason)

      Called when the test case *test* is skipped.  *reason* is the
      reason the test gave for skipping.

      The default implementation appends a tuple "(test, reason)" to
      the instance's "skipped" attribute.

   addExpectedFailure(test, err)

      Called when the test case *test* fails, but was marked with the
      "expectedFailure()" decorator.

      The default implementation appends a tuple "(test,
      formatted_err)" to the instance's "expectedFailures" attribute,
      where *formatted_err* is a formatted traceback derived from
      *err*.

   addUnexpectedSuccess(test)

      Called when the test case *test* was marked with the
      "expectedFailure()" decorator, but succeeded.

      The default implementation appends the test to the instance's
      "unexpectedSuccesses" attribute.

   addSubTest(test, subtest, outcome)

      Called when a subtest finishes.  *test* is the test case
      corresponding to the test method.  *subtest* is a custom
      "TestCase" instance describing the subtest.

      If *outcome* is "None", the subtest succeeded.  Otherwise, it
      failed with an exception where *outcome* is a tuple of the form
      returned by "sys.exc_info()": "(type, value, traceback)".

      The default implementation does nothing when the outcome is a
      success, and records subtest failures as normal failures.

      3.4 新版功能.

class unittest.TextTestResult(stream, descriptions, verbosity)

   A concrete implementation of "TestResult" used by the
   "TextTestRunner".

   3.2 新版功能: This class was previously named "_TextTestResult".
   The old name still exists as an alias but is deprecated.

unittest.defaultTestLoader

   Instance of the "TestLoader" class intended to be shared.  If no
   customization of the "TestLoader" is needed, this instance can be
   used instead of repeatedly creating new instances.

class unittest.TextTestRunner(stream=None, descriptions=True, verbosity=1, failfast=False, buffer=False, resultclass=None, warnings=None, *, tb_locals=False)

   A basic test runner implementation that outputs results to a
   stream. If *stream* is "None", the default, "sys.stderr" is used as
   the output stream. This class has a few configurable parameters,
   but is essentially very simple.  Graphical applications which run
   test suites should provide alternate implementations. Such
   implementations should accept "**kwargs" as the interface to
   construct runners changes when features are added to unittest.

   By default this runner shows "DeprecationWarning",
   "PendingDeprecationWarning", "ResourceWarning" and "ImportWarning"
   even if they are ignored by default. Deprecation warnings caused by
   deprecated unittest methods are also special-cased and, when the
   warning filters are "'default'" or "'always'", they will appear
   only once per-module, in order to avoid too many warning messages.
   This behavior can be overridden using Python's "-Wd" or "-Wa"
   options (see Warning control) and leaving *warnings* to "None".

   在 3.2 版更改: Added the "warnings" argument.

   在 3.2 版更改: The default stream is set to "sys.stderr" at
   instantiation time rather than import time.

   在 3.5 版更改: Added the tb_locals parameter.

   _makeResult()

      This method returns the instance of "TestResult" used by
      "run()". It is not intended to be called directly, but can be
      overridden in subclasses to provide a custom "TestResult".

      "_makeResult()" instantiates the class or callable passed in the
      "TextTestRunner" constructor as the "resultclass" argument. It
      defaults to "TextTestResult" if no "resultclass" is provided.
      The result class is instantiated with the following arguments:

         stream, descriptions, verbosity

   run(test)

      This method is the main public interface to the
      *TextTestRunner*. This method takes a "TestSuite" or "TestCase"
      instance. A "TestResult" is created by calling "_makeResult()"
      and the test(s) are run and the results printed to stdout.

unittest.main(module='__main__', defaultTest=None, argv=None, testRunner=None, testLoader=unittest.defaultTestLoader, exit=True, verbosity=1, failfast=None, catchbreak=None, buffer=None, warnings=None)

   A command-line program that loads a set of tests from *module* and
   runs them; this is primarily for making test modules conveniently
   executable. The simplest use for this function is to include the
   following line at the end of a test script:

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

   You can run tests with more detailed information by passing in the
   verbosity argument:

      if __name__ == '__main__':
          unittest.main(verbosity=2)

   The *defaultTest* argument is either the name of a single test or
   an iterable of test names to run if no test names are specified via
   *argv*.  If not specified or "None" and no test names are provided
   via *argv*, all tests found in *module* are run.

   The *argv* argument can be a list of options passed to the program,
   with the first element being the program name.  If not specified or
   "None", the values of "sys.argv" are used.

   The *testRunner* argument can either be a test runner class or an
   already created instance of it. By default "main" calls
   "sys.exit()" with an exit code indicating success or failure of the
   tests run.

   The *testLoader* argument has to be a "TestLoader" instance, and
   defaults to "defaultTestLoader".

   "main" supports being used from the interactive interpreter by
   passing in the argument "exit=False". This displays the result on
   standard output without calling "sys.exit()":

      >>> from unittest import main
      >>> main(module='test_module', exit=False)

   The *failfast*, *catchbreak* and *buffer* parameters have the same
   effect as the same-name command-line options.

   The *warnings* argument specifies the warning filter that should be
   used while running the tests.  If it's not specified, it will
   remain "None" if a "-W" option is passed to **python** (see Warning
   control), otherwise it will be set to "'default'".

   Calling "main" actually returns an instance of the "TestProgram"
   class. This stores the result of the tests run as the "result"
   attribute.

   在 3.1 版更改: The *exit* parameter was added.

   在 3.2 版更改: The *verbosity*, *failfast*, *catchbreak*, *buffer*
   and *warnings* parameters were added.

   在 3.4 版更改: The *defaultTest* parameter was changed to also
   accept an iterable of test names.


26.4.8.3.1. load_tests Protocol
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

3.2 新版功能.

Modules or packages can customize how tests are loaded from them
during normal test runs or test discovery by implementing a function
called "load_tests".

If a test module defines "load_tests" it will be called by
"TestLoader.loadTestsFromModule()" with the following arguments:

   load_tests(loader, standard_tests, pattern)

where *pattern* is passed straight through from "loadTestsFromModule".
It defaults to "None".

It should return a "TestSuite".

*loader* is the instance of "TestLoader" doing the loading.
*standard_tests* are the tests that would be loaded by default from
the module. It is common for test modules to only want to add or
remove tests from the standard set of tests. The third argument is
used when loading packages as part of test discovery.

A typical "load_tests" function that loads tests from a specific set
of "TestCase" classes may look like:

   test_cases = (TestCase1, TestCase2, TestCase3)

   def load_tests(loader, tests, pattern):
       suite = TestSuite()
       for test_class in test_cases:
           tests = loader.loadTestsFromTestCase(test_class)
           suite.addTests(tests)
       return suite

If discovery is started in a directory containing a package, either
from the command line or by calling "TestLoader.discover()", then the
package "__init__.py" will be checked for "load_tests".  If that
function does not exist, discovery will recurse into the package as
though it were just another directory.  Otherwise, discovery of the
package's tests will be left up to "load_tests" which is called with
the following arguments:

   load_tests(loader, standard_tests, pattern)

This should return a "TestSuite" representing all the tests from the
package. ("standard_tests" will only contain tests collected from
"__init__.py".)

Because the pattern is passed into "load_tests" the package is free to
continue (and potentially modify) test discovery. A 'do nothing'
"load_tests" function for a test package would look like:

   def load_tests(loader, standard_tests, pattern):
       # top level directory cached on loader instance
       this_dir = os.path.dirname(__file__)
       package_tests = loader.discover(start_dir=this_dir, pattern=pattern)
       standard_tests.addTests(package_tests)
       return standard_tests

在 3.5 版更改: Discovery no longer checks package names for matching
*pattern* due to the impossibility of package names matching the
default pattern.


26.4.9. Class and Module Fixtures
=================================

Class and module level fixtures are implemented in "TestSuite". When
the test suite encounters a test from a new class then
"tearDownClass()" from the previous class (if there is one) is called,
followed by "setUpClass()" from the new class.

Similarly if a test is from a different module from the previous test
then "tearDownModule" from the previous module is run, followed by
"setUpModule" from the new module.

After all the tests have run the final "tearDownClass" and
"tearDownModule" are run.

Note that shared fixtures do not play well with [potential] features
like test parallelization and they break test isolation. They should
be used with care.

The default ordering of tests created by the unittest test loaders is
to group all tests from the same modules and classes together. This
will lead to "setUpClass" / "setUpModule" (etc) being called exactly
once per class and module. If you randomize the order, so that tests
from different modules and classes are adjacent to each other, then
these shared fixture functions may be called multiple times in a
single test run.

Shared fixtures are not intended to work with suites with non-standard
ordering. A "BaseTestSuite" still exists for frameworks that don't
want to support shared fixtures.

If there are any exceptions raised during one of the shared fixture
functions the test is reported as an error. Because there is no
corresponding test instance an "_ErrorHolder" object (that has the
same interface as a "TestCase") is created to represent the error. If
you are just using the standard unittest test runner then this detail
doesn't matter, but if you are a framework author it may be relevant.


26.4.9.1. setUpClass and tearDownClass
--------------------------------------

These must be implemented as class methods:

   import unittest

   class Test(unittest.TestCase):
       @classmethod
       def setUpClass(cls):
           cls._connection = createExpensiveConnectionObject()

       @classmethod
       def tearDownClass(cls):
           cls._connection.destroy()

If you want the "setUpClass" and "tearDownClass" on base classes
called then you must call up to them yourself. The implementations in
"TestCase" are empty.

If an exception is raised during a "setUpClass" then the tests in the
class are not run and the "tearDownClass" is not run. Skipped classes
will not have "setUpClass" or "tearDownClass" run. If the exception is
a "SkipTest" exception then the class will be reported as having been
skipped instead of as an error.


26.4.9.2. setUpModule and tearDownModule
----------------------------------------

These should be implemented as functions:

   def setUpModule():
       createConnection()

   def tearDownModule():
       closeConnection()

If an exception is raised in a "setUpModule" then none of the tests in
the module will be run and the "tearDownModule" will not be run. If
the exception is a "SkipTest" exception then the module will be
reported as having been skipped instead of as an error.


26.4.10. 信号处理
=================

3.2 新版功能.

The "-c/--catch" command-line option to unittest, along with the
"catchbreak" parameter to "unittest.main()", provide more friendly
handling of control-C during a test run. With catch break behavior
enabled control-C will allow the currently running test to complete,
and the test run will then end and report all the results so far. A
second control-c will raise a "KeyboardInterrupt" in the usual way.

The control-c handling signal handler attempts to remain compatible
with code or tests that install their own "signal.SIGINT" handler. If
the "unittest" handler is called but *isn't* the installed
"signal.SIGINT" handler, i.e. it has been replaced by the system under
test and delegated to, then it calls the default handler. This will
normally be the expected behavior by code that replaces an installed
handler and delegates to it. For individual tests that need "unittest"
control-c handling disabled the "removeHandler()" decorator can be
used.

There are a few utility functions for framework authors to enable
control-c handling functionality within test frameworks.

unittest.installHandler()

   Install the control-c handler. When a "signal.SIGINT" is received
   (usually in response to the user pressing control-c) all registered
   results have "stop()" called.

unittest.registerResult(result)

   Register a "TestResult" object for control-c handling. Registering
   a result stores a weak reference to it, so it doesn't prevent the
   result from being garbage collected.

   Registering a "TestResult" object has no side-effects if control-c
   handling is not enabled, so test frameworks can unconditionally
   register all results they create independently of whether or not
   handling is enabled.

unittest.removeResult(result)

   Remove a registered result. Once a result has been removed then
   "stop()" will no longer be called on that result object in response
   to a control-c.

unittest.removeHandler(function=None)

   When called without arguments this function removes the control-c
   handler if it has been installed. This function can also be used as
   a test decorator to temporarily remove the handler while the test
   is being executed:

      @unittest.removeHandler
      def test_signal_handling(self):
          ...
