# 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

  A test fixture represents the preparation needed to perform one or more tests, and any associate cleanup actions. This may involve, for example, creating temporary or proxy databases, directories, or starting a server process.

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。

Simple Smalltalk Testing: With Patterns

  Kent Beck’s original paper on testing frameworks using the pattern shared by `unittest`.

Nose 和 pytest

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

The Python Testing Tools Taxonomy

  An extensive list of Python testing tools including functional testing frameworks and mock object libraries.

Testing in Python Mailing List

  A special-interest-group for discussion of testing, and testing tools, in Python.

The script `Tools/unittestgui/unittestgui.py` in the Python source distribution is a GUI tool for test discovery and execution. This is intended largely for ease of use for those new to unit testing. For production environments it is recommended that tests be driven by a continuous integration system such as Buildbot, Jenkins or 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。

It is recommended that you use TestCase implementations to group tests together according to the features they test. `unittest` provides a mechanism for this: the test suite, represented by `unittest`’s `TestSuite` class. In most cases, calling `unittest.main()` will do the right thing and collect all the module’s test cases for you and execute them.

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())

You can place the definitions of test cases and test suites in the same modules as the code they are to test (such as `widget.py`), but there are several advantages to placing the test code in a separate module, such as `test_widget.py`:

- The test module can be run standalone from the command line.

- The test code can more easily be separated from shipped code.

- There is less temptation to change test code to fit the code it tests without a good reason.

- Test code should be modified much less frequently than the code it tests.

- Tested code can be refactored more easily.

- Tests for modules written in C must be in separate modules anyway, so why not be consistent?

- If the testing strategy changes, there is no need to change the source code.

## 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

Even though `FunctionTestCase` can be used to quickly convert an existing test base over to a `unittest`-based system, this approach is not recommended. Taking the time to set up proper `TestCase` subclasses will make future test refactorings infinitely easier.

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 supports skipping individual test methods and even whole classes of tests. In addition, it supports marking a test as an “expected failure,” a test that is broken and will fail, but shouldn’t be counted as a failure on a `TestResult`.

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

Without using a subtest, execution would stop after the first failure, and the error would be less easy to diagnose because the value of `i` wouldn’t be displayed:

    ======================================================================
    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.

  Methods in the first group (running the test) are:

  `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 the message matches regex r | 3.1
  `assertWarns(warn, fun, *args, **kwds)` | `fun(*args, **kwds)` raises warn | 3.2
  `assertWarnsRegex(warn, r, fun, *args, **kwds)` | `fun(*args, **kwds)` raises warn and the message matches regex r | 3.2
  `assertLogs(logger, level)` | The `with` block logs on logger with minimum level | 3.4

  `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 elements in the same number, regardless of their order | 3.2

  `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)

    Test that a regex search matches (or does not match) text. In case of failure, the error message will include the pattern and the text (or the pattern and the part of text that unexpectedly matched). regex may be a regular expression object or a string containing a regular expression suitable for use by `re.search()`.

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

    在 3.2 版更改: The method `assertRegexpMatches()` has been renamed to `assertRegex()`.

    3.2 新版功能: `assertNotRegex()`

    3.5 新版功能: The name `assertNotRegexpMatches` is a deprecated alias for `assertNotRegex()`.

  `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.

  The list of type-specific methods automatically used by `assertEqual()` are summarized in the following table. Note that it’s usually not necessary to invoke these methods directly.

  Method | Used to compare | New in
  --- | --- | ---
  `assertMultiLineEqual(a, b)` | strings | 3.1
  `assertSequenceEqual(a, b)` | sequences | 3.1
  `assertListEqual(a, b)` | lists | 3.1
  `assertTupleEqual(a, b)` | tuples | 3.1
  `assertSetEqual(a, b)` | sets or frozensets | 3.1
  `assertDictEqual(a, b)` | dicts | 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). 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. Signal Handling

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):
          ...