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。

• Simple Smalltalk Testing: With Patterns

• Kent Beck's original paper on testing frameworks using the pattern sharedby unittest.

• pytest

• Third-party unittest framework with a lighter-weight syntax for writingtests. For example, assert func(10) == 42.

• The Python Testing Tools Taxonomy

• An extensive list of Python testing tools including functional testingframeworks 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 isa GUI tool for test discovery and execution. This is intended largely for ease of usefor those new to unit testing. For production environments it isrecommended that tests be driven by a continuous integration system such asBuildbot, Jenkinsor Hudson.

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。

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。

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。

• -k

• 只运行匹配模式或子串的测试方法和类。可以多次使用这个选项，以便包含匹配子串的所有测试用例。

包含通配符（*）的模式使用 fnmatch.fnmatchcase() 对测试名称进行匹配。另外，该匹配是大小写敏感的。

模式对测试加载器导入的测试方法全名进行匹配。

例如，-k foo 可以匹配到 foo_tests.SomeTest.test_something 和 bar_tests.SomeTest.test_foo ，但是不能匹配到 bar_tests.FooTest.test_something 。

• —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 。

3.7 新版功能: 命令行选项 -k 。

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。

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 ）。

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 togetheraccording to the features they test. unittest provides a mechanism forthis: the test suite, represented by unittest'sTestSuite class. In most cases, calling unittest.main() will dothe right thing and collect all the module's test cases for you and executethem.

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 modulesas the code they are to test (such as widget.py), but there are severaladvantages to placing the test code in a separate module, such astest_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 withouta 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 notbe consistent?

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

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 anexisting test base over to a unittest-based system, this approach isnot recommended. Taking the time to set up proper TestCasesubclasses will make future test refactorings infinitely easier.

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

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 oftests. In addition, it supports marking a test as an "expected failure," a testthat is broken and will fail, but shouldn't be counted as a failure on aTestResult.

Skipping a test is simply a matter of using the skip()decoratoror one of its conditional variants, calling TestCase.skipTest() within asetUp() or test method, or raising SkipTest directly.

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
 
    def test_maybe_skipped(self):
        if not external_resource_available():
            self.skipTest("external resource not available")
        # test code that depends on the external resource
        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_maybe_skipped (__main__.MyTestCase) ... skipped 'external resource not available'
test_windows_support (__main__.MyTestCase) ... skipped 'requires Windows'
 
----------------------------------------------------------------------
Ran 4 tests in 0.005s
 
OK (skipped=4)

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 callsskip() on the test when it wants it to be skipped. This decorator skipsthe 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 and exception 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

• 把测试标记为预计失败。如果测试不通过，会被认为测试成功；如果测试通过了，则被认为是测试失败。

• 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。

Distinguishing test iterations using subtests

3.4 新版功能.

When there are very small differences among your tests, forinstance some parameters, unittest allows you to distinguish them insidethe 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 iwouldn'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

类与函数

本节深入介绍了 unittest 的 API。

测试用例

• class unittest.TestCase(methodName='runTest')
• Instances of the TestCase class represent the logical test unitsin the unittest universe. This class is intended to be used as a baseclass, with specific tests being implemented by concrete subclasses. This classimplements the interface needed by the test runner to allow it to drive thetests, and methods that the test code can use to check for and report variouskinds of failure.

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

在 3.2 版更改: TestCase can be instantiated successfully without providing amethodName. This makes it easier to experiment with TestCasefrom the interactive interpreter.

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

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

• setUp()

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

• tearDown()

• Method called immediately after the test method has been called and theresult recorded. This is called even if the test method raised anexception, so the implementation in subclasses may need to be particularlycareful about checking internal state. Any exception, other thanAssertionError or SkipTest, raised by this method will beconsidered an additional error rather than a test failure (thus increasingthe total number of reported errors). This method will only be called ifthe 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 argumentand must be decorated as a classmethod():

@classmethoddef 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 argumentand must be decorated as a classmethod():

@classmethoddef 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 objectpassed as result. If result is omitted or None, a temporaryresult object is created (by calling the defaultTestResult()method) and used. The result object is returned to run()'scaller.

The same effect may be had by simply calling the TestCaseinstance.

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

• skipTest(reason)
• Calling this during a test method or setUp() skips the currenttest. 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 asubtest. msg and params are optional, arbitrary values which aredisplayed whenever a subtest fails, allowing you to identify themclearly.

A test case can contain any number of subtest declarations, andthey 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 raisedby the test to be propagated to the caller, and can be used to supportrunning tests under a debugger.

The TestCase class provides several assert methods to check for andreport 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 usedas 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 notcompare equal, the test will fail.

In addition, if first and second are the exact same type and one oflist, tuple, dict, set, frozenset or str or any type that a subclassregisters with addTypeEqualityFunc() the type-specific equalityfunction will be called in order to generate a more useful defaulterror 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 equalityfunction for comparing strings.

• assertNotEqual(first, second, msg=None)

• Test that first and second are not equal. If the values docompare 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 expris True (use assertIs(expr, True) for the latter). This methodshould also be avoided when more specific methods are available (e.g.assertEqual(a, b) instead of assertTrue(a == b)), because theyprovide 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 thesame 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 aclass 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, andlog 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 anypositional or keyword arguments that are also passed toassertRaises(). The test passes if exception is raised, is anerror if another exception is raised, or fails if no exception is raised.To catch any of a group of exceptions, a tuple containing the exceptionclasses 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 writteninline rather than as a function:

with self.assertRaises(SomeException):
    do_something()

When used as a context manager, assertRaises() accepts theadditional keyword argument msg.

The context manager will store the caught exception object in itsexception attribute. This can be useful if the intentionis 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 matcheson the string representation of the raised exception. regex may bea regular expression object or a string containing a regular expressionsuitable 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: Added 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 anypositional or keyword arguments that are also passed toassertWarns(). The test passes if warning is triggered andfails if it isn't. Any exception is an error.To catch any of a group of warnings, a tuple containing the warningclasses 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 writteninline rather than as a function:

with self.assertWarns(SomeWarning):
    do_something()

When used as a context manager, assertWarns() accepts theadditional keyword argument msg.

The context manager will store the caught warning object in itswarning attribute, and the source line which triggered thewarnings in the filename and lineno attributes.This can be useful if the intention is to perform additional checkson 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 itis 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 themessage of the triggered warning. regex may be a regular expressionobject or a string containing a regular expression suitable for useby 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 onthe logger or one of its children, with at least the givenlevel.

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

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

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

The object returned by the context manager is a recording helperwhich keeps tracks of the matching log messages. It has twoattributes:

- <code>records</code>[](https://docs.python.org/zh-cn/3/library/#unittest.TestCase.records)
- 

A list of logging.LogRecord objects of the matchinglog messages.

- <code>output</code>[](https://docs.python.org/zh-cn/3/library/#unittest.TestCase.output)
- 

A list of str objects with the formatted output ofmatching 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 sameelements 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 ofdecimal places (default 7), and comparing to zero. Note that thesemethods 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 differencebetween 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 objectsthat compare equal. assertNotAlmostEqual() automatically failsif 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 dependingon 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 caseof failure, the error message will include the pattern and the text (orthe pattern and the part of text that unexpectedly matched). _regex_may be a regular expression object or a string containing a regularexpression suitable for use by re.search().

3.1 新版功能: Added under the name assertRegexpMatches.

在 3.2 版更改: The method assertRegexpMatches() has been renamed toassertRegex().

3.2 新版功能: assertNotRegex()

3.5 新版功能: The name assertNotRegexpMatches is a deprecated aliasfor 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 thedifferences between the sequences will be generated.

Duplicate elements are not ignored when comparing first andsecond. It verifies whether each element has the same count in bothsequences. 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 ofthe same type to different type-specific methods. These methods are alreadyimplemented for most of the built-in types, but it's also possible toregister new methods using addTypeEqualityFunc():

• addTypeEqualityFunc(typeobj, function)
• Registers a type-specific method called by assertEqual() to checkif two objects of exactly the same typeobj (not subclasses) compareequal. function must take two positional arguments and a third msg=Nonekeyword argument just as assertEqual() does. It must raiseself.failureException(msg) when inequalitybetween the first two parameters is detected — possibly providing usefulinformation and explaining the inequalities in details in the errormessage.

3.1 新版功能.

The list of type-specific methods automatically used byassertEqual() are summarized in the following table. Notethat 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 differenceswill be included in the error message. This method is used by defaultwhen 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, bothfirst and second must be instances of seq_type or a failure willbe raised. If the sequences are different an error message isconstructed that shows the difference between the two.

This method is not called directly by assertEqual(), butit's used to implement assertListEqual() andassertTupleEqual().

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 isconstructed that shows only the differences between the two. An erroris also raised if either of the parameters are of the wrong type.These methods are used by default when comparing lists or tuples withassertEqual().

3.1 新版功能.

• assertSetEqual(first, second, msg=None)
• Tests that two sets are equal. If not, an error message is constructedthat lists the differences between the sets. This method is used bydefault 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 isconstructed that shows the differences in the dictionaries. Thismethod will be used by default to compare dictionaries incalls 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 forthe error message.

• failureException

• This class attribute gives the exception raised by the test method. If atest framework needs to use a specialized exception, possibly to carryadditional information, it must subclass this exception in order to "playfair" with the framework. The initial value of this attribute isAssertionError.

• longMessage

• This class attribute determines what happens when a custom failure messageis passed as the msg argument to an assertXYY call that fails.True is the default value. In this case, the custom message is appendedto 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 assigningan instance attribute, self.longMessage, to True or False beforecalling 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 assertmethods that report diffs on failure. It defaults to 80*8 characters.Assert methods affected by this attribute areassertSequenceEqual() (including all the sequence comparisonmethods that delegate to it), assertDictEqual() andassertMultiLineEqual().

Setting maxDiff to None means that there is no maximum length ofdiffs.

3.2 新版功能.

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

• countTestCases()

• Return the number of tests represented by this test object. ForTestCase instances, this will always be 1.

• defaultTestResult()

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

For TestCase instances, this will always be an instance ofTestResult; subclasses of TestCase should override thisas necessary.

• id()

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

• shortDescription()

• Returns a description of the test, or None if no descriptionhas been provided. The default implementation of this methodreturns 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 descriptioneven in the presence of a docstring. This caused compatibility issueswith unittest extensions and adding the test name was moved to theTextTestResult in Python 3.2.

• addCleanup(function, *args, **kwargs)
• Add a function to be called after tearDown() to cleanup resourcesused during the test. Functions will be called in reverse order to theorder they are added (LIFO). Theyare called with any arguments and keyword arguments passed intoaddCleanup() 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(), orafter setUp() if setUp() raises an exception.

It is responsible for calling all the cleanup functions added byaddCleanup(). If you need cleanup functions to be calledprior to tearDown() then you can call doCleanups()yourself.

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

3.1 新版功能.

• classmethod addClassCleanup(function, /, *args, **kwargs)
• Add a function to be called after tearDownClass() to cleanupresources used during the test class. Functions will be called in reverseorder to the order they are added (LIFO).They are called with any arguments and keyword arguments passed intoaddClassCleanup() when they are added.

If setUpClass() fails, meaning that tearDownClass() is notcalled, then any cleanup functions added will still be called.

3.8 新版功能.

• classmethod doClassCleanups()
• This method is called unconditionally after tearDownClass(), orafter setUpClass() if setUpClass() raises an exception.

It is responsible for calling all the cleanup functions added byaddCleanupClass(). If you need cleanup functions to be calledprior to tearDownClass() then you can calldoCleanupsClass() yourself.

doCleanupsClass() pops methods off the stack of cleanupfunctions one at a time, so it can be called at any time.

3.8 新版功能.

• class unittest.IsolatedAsyncioTestCase(methodName='runTest')
• This class provides an API similar to TestCase and also acceptscoroutines as test functions.

3.8 新版功能.

• coroutine asyncSetUp()

• Method called to prepare the test fixture. This is called after setUp().This is called immediately before calling the test method; other thanAssertionError or SkipTest, any exception raised by this methodwill be considered an error rather than a test failure. The default implementationdoes nothing.

• coroutine asyncTearDown()

• Method called immediately after the test method has been called and theresult recorded. This is called before tearDown(). This is called even ifthe test method raised an exception, so the implementation in subclasses may needto be particularly careful about checking internal state. Any exception, other thanAssertionError or SkipTest, raised by this method will beconsidered an additional error rather than a test failure (thus increasingthe total number of reported errors). This method will only be called ifthe asyncSetUp() succeeds, regardless of the outcome of the test method.The default implementation does nothing.

• addAsyncCleanup(function, /, *args, **kwargs)

• This method accepts a coroutine that can be used as a cleanup function.

• run(result=None)

• Sets up a new event loop to run the test, collecting the result intothe TestResult object passed as result. If result isomitted or None, a temporary result object is created (by callingthe defaultTestResult() method) and used. The result object isreturned to run()'s caller. At the end of the test all the tasksin the event loop are cancelled.

An example illustrating the order:

from unittest import IsolatedAsyncioTestCase
 
events = []
 
 
class Test(IsolatedAsyncioTestCase):
 
 
    def setUp(self):
        events.append("setUp")
 
    async def asyncSetUp(self):
        self._async_connection = await AsyncConnection()
        events.append("asyncSetUp")
 
    async def test_response(self):
        events.append("test_response")
        response = await self._async_connection.get("https://example.com")
        self.assertEqual(response.status_code, 200)
        self.addAsyncCleanup(self.on_cleanup)
 
    def tearDown(self):
        events.append("tearDown")
 
    async def asyncTearDown(self):
        await self._async_connection.close()
        events.append("asyncTearDown")
 
    async def on_cleanup(self):
        events.append("cleanup")
 
if __name__ == "__main__":
    unittest.main()

After running the test, events would contain ["setUp", "asyncSetUp", "test_response", "asyncTearDown", "tearDown", "cleanup"].

• class unittest.FunctionTestCase(testFunc, setUp=None, tearDown=None, description=None)
• This class implements the portion of the TestCase interface whichallows the test runner to drive the test, but does not provide the methodswhich test code can use to check and report errors. This is used to createtest cases using legacy test code, allowing it to be integrated into aunittest-based test framework.

Deprecated aliases

For historical reasons, some of the TestCase methods had one or morealiases that are now deprecated. The following table lists the correct namesalong 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 have been deprecated.

3.2 版后已移除: The assert aliases listed in the third column have been deprecated.

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

3.5 版后已移除: The assertNotRegexpMatches name is deprecated in favor of assertNotRegex().

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 runas any other test case. Running a TestSuite instance is the same asiterating over the suite, running each test individually.

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

TestSuite objects behave much like TestCase objects, exceptthey do not actually implement a test. Instead, they are used to aggregatetests into groups of tests that should be run together. Some additionalmethods 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 TestSuiteinstances to this test suite.

This is equivalent to iterating over tests, calling addTest() foreach element.

TestSuite shares the following methods with TestCase:

• run(result)

• Run the tests associated with this suite, collecting the result into thetest result object passed as result. Note that unlikeTestCase.run(), TestSuite.run() requires the result object tobe passed in.

• debug()

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

• countTestCases()

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

• iter()

• Tests grouped by a TestSuite are always accessed by iteration.Subclasses can lazily provide tests by overriding iter(). Notethat this method may be called several times on a single suite (forexample when counting tests or comparing for equality) so the testsreturned by repeated iterations before TestSuite.run() must be thesame for each call iteration. After TestSuite.run(), callers shouldnot rely on the tests returned by this method unless the caller uses asubclass that overrides TestSuite._removeTestAtIndex() to preservetest references.

在 3.2 版更改: In earlier versions the TestSuite accessed tests directly ratherthan through iteration, so overriding iter() wasn't sufficientfor providing tests.

在 3.4 版更改: In earlier versions the TestSuite held references to eachTestCase after TestSuite.run(). Subclasses can restorethat behavior by overriding TestSuite._removeTestAtIndex().

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

Loading and running tests

• class unittest.TestLoader
• The TestLoader class is used to create test suites from classes andmodules. Normally, there is no need to create an instance of this class; theunittest module provides an instance that can be shared asunittest.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 resetby the loader at any point. Fatal errors are signalled by the relevanta method raising an exception to the caller. Non-fatal errors are alsoindicated by a synthetic test that will raise the original error whenrun.

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-derivedtestCaseClass.

A test case instance is created for each method named bygetTestCaseNames(). By default these are the method namesbeginning with test. If getTestCaseNames() returns nomethods, but the runTest() method is implemented, a single testcase is created for that method instead.

• loadTestsFromModule(module, pattern=None)
• Return a suite of all test cases contained in the given module. Thismethod searches module for classes derived from TestCase andcreates an instance of the class for each test method defined for theclass.

注解

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

If a module provides a loadtests function it will be called toload the tests. This allows modules to customize test loading.This is the load_tests protocol. The _pattern argument is passed asthe 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 isdeprecated and ignored, although it is still accepted for backwardcompatibility. The method also now accepts a keyword-only argumentpattern 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 amodule, a test case class, a test method within a test case class, aTestSuite instance, or a callable object which returns aTestCase or TestSuite instance. These checks areapplied in the order listed here; that is, a method on a possible testcase 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 aTestCase-derived class SampleTestCase with three testmethods (test_one(), test_two(), and test_three()), thespecifier 'SampleTests.SampleTestCase' would cause this method toreturn a suite which will run all three test methods. Using the specifier'SampleTests.SampleTestCase.test_two' would cause it to return a testsuite which will run only the test_two() test method. The specifiercan refer to modules and packages which have not been imported; they willbe 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 traversingname then a synthetic test that raises that error when run will bereturned. These errors are included in the errors accumulated byself.errors.

• loadTestsFromNames(names, module=None)

• Similar to loadTestsFromName(), but takes a sequence of names ratherthan a single name. The return value is a test suite which supports allthe 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 thespecified start directory, and return a TestSuite object containing them.Only test files that match pattern will be loaded. (Using shell stylepattern matching.) Only module names that are importable (i.e. are validPython identifiers) will be loaded.

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

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

If a package (a directory containing a file named init.py) isfound, the package will be checked for a load_tests function. If thisexists then it will be calledpackage.load_tests(loader, tests, pattern). Test discovery takes careto ensure that a package is only checked for tests once during aninvocation, even if the load_tests function itself callsloader.discover.

If loadtests exists then discovery does _not recurse into thepackage, load_tests is responsible for loading all tests in thepackage.

The pattern is deliberately not stored as a loader attribute so thatpackages can continue discovery themselves. top_level_dir is stored soload_tests does not need to pass this argument in toloader.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 loadtests regardless ofwhether their path matches _pattern, because it is impossible fora package name to match the default pattern.

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

• testMethodPrefix
• String giving the prefix of method names which will be interpreted as testmethods. 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 ingetTestCaseNames() and all the loadTestsFrom*() methods.

• suiteClass

• Callable object that constructs a test suite from a list of tests. Nomethods on the resulting object are needed. The default value is theTestSuite class.

This affects all the loadTestsFrom*() methods.

• testNamePatterns
• List of Unix shell-style wildcard test name patterns that test methodshave to match to be included in test suites (see -v option).

If this attribute is not None (the default), all test methods to beincluded in test suites must match one of the patterns in this list.Note that matches are always performed using fnmatch.fnmatchcase(),so unlike patterns passed to the -v option, simple substring patternswill have to be converted using * wildcards.

This affects all the loadTestsFrom*() methods.

3.7 新版功能.

• class unittest.TestResult
• This class is used to compile information about which tests have succeededand which have failed.

A TestResult object stores the results of a set of tests. TheTestCase and TestSuite classes ensure that results areproperly recorded; test authors do not need to worry about recording theoutcome of tests.

Testing frameworks built on top of unittest may want access to theTestResult object generated by running a set of tests for reportingpurposes; a TestResult instance is returned by theTestRunner.run() method for this purpose.

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

• errors

• A list containing 2-tuples of TestCase instances and stringsholding formatted tracebacks. Each tuple represents a test which raised anunexpected exception.

• failures

• A list containing 2-tuples of TestCase instances and stringsholding formatted tracebacks. Each tuple represents a test where a failurewas explicitly signalled using the TestCase.assert*() methods.

• skipped

• A list containing 2-tuples of TestCase instances and stringsholding the reason for skipping the test.

3.1 新版功能.

• expectedFailures

• A list containing 2-tuples of TestCase instances and stringsholding formatted tracebacks. Each tuple represents an expected failureof the test case.

• unexpectedSuccesses

• A list containing TestCase instances that were marked as expectedfailures, 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 betweenstartTest() and stopTest() being called. Collected output willonly be echoed onto the real sys.stdout and sys.stderr if the testfails 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 returnsFalse.

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

• stop()
• This method can be called to signal that the set of tests being run shouldbe aborted by setting the shouldStop attribute to True.TestRunner objects should respect this flag and return withoutrunning any additional tests.

For example, this feature is used by the TextTestRunner class tostop the test framework when the user signals an interrupt from thekeyboard. Interactive tools which provide TestRunnerimplementations can use this in a similar manner.

The following methods of the TestResult class are used to maintainthe internal data structures, and may be extended in subclasses to supportadditional reporting requirements. This is particularly useful in buildingtools 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 theoutcome.

• 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 atuple of the form returned by sys.exc_info(): (type, value,traceback).

The default implementation appends a tuple (test, formattederr) tothe instance's errors attribute, where _formatted_err is aformatted traceback derived from err.

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

The default implementation appends a tuple (test, formattederr) tothe instance's failures attribute, where _formatted_err is aformatted 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 thetest gave for skipping.

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

• addExpectedFailure(test, err)
• Called when the test case test fails, but was marked with theexpectedFailure() decorator.

The default implementation appends a tuple (test, formattederr) tothe 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 theexpectedFailure() decorator, but succeeded.

The default implementation appends the test to the instance'sunexpectedSuccesses attribute.

• addSubTest(test, subtest, outcome)
• Called when a subtest finishes. test is the test casecorresponding to the test method. subtest is a customTestCase instance describing the subtest.

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

The default implementation does nothing when the outcome is asuccess, 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 theTextTestRunner.

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

• unittest.defaultTestLoader

• Instance of the TestLoader class intended to be shared. If nocustomization of the TestLoader is needed, this instance can be usedinstead 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 classhas a few configurable parameters, but is essentially very simple. Graphicalapplications which run test suites should provide alternate implementations. Suchimplementations should accept **kwargs as the interface to construct runnerschanges when features are added to unittest.

By default this runner shows DeprecationWarning,PendingDeprecationWarning, ResourceWarning andImportWarning even if they are ignored by default. Deprecation warnings caused by deprecated unittestmethods are also special-cased and, when the warningfilters are 'default' or 'always', they will appear only onceper-module, in order to avoid too many warning messages. This behavior canbe overridden using Python's -Wd or -Wa options(see Warning control) and leavingwarnings 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 ratherthan 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 insubclasses to provide a custom TestResult.

_makeResult() instantiates the class or callable passed in theTextTestRunner constructor as the resultclass argument. Itdefaults 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. Thismethod takes a TestSuite or TestCase instance. ATestResult is created by calling_makeResult() and the test(s) are run and theresults 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 theend of a test script:

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

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

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

The defaultTest argument is either the name of a single test or aniterable of test names to run if no test names are specified via argv. Ifnot specified or None and no test names are provided via argv, alltests found in module are run.

The argv argument can be a list of options passed to the program, with thefirst 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 alreadycreated instance of it. By default main calls sys.exit() withan 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 theargument exit=False. This displays the result on standard output withoutcalling sys.exit():

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

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

The warnings argument specifies the warning filterthat should be used while running the tests. If it's not specified, it willremain 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 oftest names.

load_tests Protocol

3.2 新版功能.

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

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

load_tests(loader, standard_tests, pattern)

where pattern is passed straight through from loadTestsFromModule. Itdefaults 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 themodule. It is common for test modules to only want to add or remove testsfrom 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 ofTestCase 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 thecommand line or by calling TestLoader.discover(), then the packageinit.py will be checked for load_tests. If that function doesnot exist, discovery will recurse into the package as though it were justanother directory. Otherwise, discovery of the package's tests will be left upto load_tests which is called with the following arguments:

load_tests(loader, standard_tests, pattern)

This should return a TestSuite representing all the testsfrom the package. (standardtests will only contain testscollected from _init.py.)

Because the pattern is passed into load_tests the package is free tocontinue (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 theimpossibility of package names matching the default pattern.

Class and Module Fixtures

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

Similarly if a test is from a different module from the previous test thentearDownModule from the previous module is run, followed bysetUpModule from the new module.

After all the tests have run the final tearDownClass andtearDownModule are run.

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

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

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

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

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 calledthen you must call up to them yourself. The implementations inTestCase are empty.

If an exception is raised during a setUpClass then the tests in the classare not run and the tearDownClass is not run. Skipped classes will nothave setUpClass or tearDownClass run. If the exception is aSkipTest exception then the class will be reported as having been skippedinstead of as an error.

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 themodule will be run and the tearDownModule will not be run. If the exception is aSkipTest exception then the module will be reported as having been skippedinstead of as an error.

To add cleanup code that must be run even in the case of an exception, useaddModuleCleanup:

• unittest.addModuleCleanup(function, /, *args, **kwargs)
• Add a function to be called after tearDownModule() to cleanupresources used during the test class. Functions will be called in reverseorder to the order they are added (LIFO).They are called with any arguments and keyword arguments passed intoaddModuleCleanup() when they are added.

If setUpModule() fails, meaning that tearDownModule() is notcalled, then any cleanup functions added will still be called.

3.8 新版功能.

• unittest.doModuleCleanups()
• This function is called unconditionally after tearDownModule(), orafter setUpModule() if setUpModule() raises an exception.

It is responsible for calling all the cleanup functions added byaddCleanupModule(). If you need cleanup functions to be calledprior to tearDownModule() then you can calldoModuleCleanups() yourself.

doModuleCleanups() pops methods off the stack of cleanupfunctions one at a time, so it can be called at any time.

3.8 新版功能.

Signal Handling

3.2 新版功能.

The -c/—catch command-line option to unittest,along with the catchbreak parameter to unittest.main(), providemore friendly handling of control-C during a test run. With catch breakbehavior 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 secondcontrol-c will raise a KeyboardInterrupt in the usual way.

The control-c handling signal handler attempts to remain compatible with code ortests that install their own signal.SIGINT handler. If the unittesthandler 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 itcalls the default handler. This will normally be the expected behavior by codethat replaces an installed handler and delegates to it. For individual teststhat need unittest control-c handling disabled the removeHandler()decorator can be used.

There are a few utility functions for framework authors to enable control-chandling 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 resultshave stop() called.

• unittest.registerResult(result)

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

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

• unittest.removeResult(result)

• Remove a registered result. Once a result has been removed thenstop() will no longer be called on that result object inresponse to a control-c.

• unittest.removeHandler(function=None)

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

@unittest.removeHandlerdef test_signal_handling(self):    …