unittest --- 單元測試框架

源代码: Lib/unittest/__init__.py


(假如你已經熟悉相關基礎的測試概念,你可能會希望跳過以下段落,直接參考 assert 方法清單。)

unittest 原生的單元測試框架最初由 JUnit 開發,和其他程式語言相似有主要的單元測試框架。支援自動化測試,對測試分享安裝與關閉程式碼,集合所有匯總的測試,並且獨立各個測試報告框架。

unittest 用來作為實現支援一些重要的物件導向方法的概念。

test fixture

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。

test case(測試用例)

一個 test case 是一個獨立的單元測試。這是用來確認一個特定設定的輸入的特殊回饋。 unittest 提供一個基礎類別,類別 TestCase,可以用來建立一個新的測試條例。

test suite(測試套件)

test suite 是一個搜集測試條例,測試套件,或是兩者皆有。它需要一起被執行並用來匯總測試。

test runner(測試執行器)

test runner 是一個編排測試執行與提供結果給使用者的一個元件。執行器可以使用圖形化介面,文字介面或是回傳一個特別值用來標示出執行測試的結果。

也參考

doctest 模組

另一個執行測試的模組,但使用不一樣的測試方法與規範。

Simple Smalltalk Testing: With Patterns

Kent Beck 的原始論文討論使用 unittest 這樣模式的測試框架。

pytest

第三方单元测试框架,提供轻量化的语法来编写测试,例如:assert func(10) == 42

The Python Testing Tools Taxonomy

一份詳細的 Python 測試工具列表,包含 functional testing 框架和mock object 函式庫。

Testing in Python Mailing List

一個專門興趣的群組用來討論 Python 中的測試方式與測試工具。

随 Python 源代码分发的脚本 Tools/unittestgui/unittestgui.py 是一个一个用于发现和执行测试的用户图形界面工具。这主要是为了方便新手使用单元测试制作的。在生产环境中,测试应由一个持续集成(CI)系统运行,如 Buildbot, JenkinsTravis-CI, 或 AppVeyor

簡單範例

unittest 模組提供一系列豐富的工具用來建構與執行測試。本節將展示這一系列工具中一部份,它們已能滿足大部份使用者需求。

這是一段簡短的腳本用來測試 3 個字串方法:

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()

測試用例 (testcase) 可以透過繼承 unittest.TestCase 類別來建立。這裡定義了三個獨立的物件方法,名稱皆以 test 開頭。這樣的命名方式能告知 test runner 哪些物件方法為定義的測試。

每個測試的關鍵為呼叫 assertEqual() 來確認是否為期望的結果; assertTrue() 或是 assertFalse() 用來驗證一個條件式; assertRaises() 用來驗證是否觸發一個特定的 exception。使用這些物件方法來取代 assert 陳述句,將能使 test runner 收集所有的測試結果並產生一個報表。

通过 setUp()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。

最後將顯示一個簡單的方法去執行測試 unittest.main() 提供一個命令執行列介面測試腳本。當透過命令執行列執行,輸出結果將會像是:

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

OK

在測試時加入 -v 選項將指示 unittest.main() 提高 verbosity 層級,產生以下的輸出:

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

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

OK

以上的例子顯示大多數使用 unittest 特徵足以滿足大多數日常測試的需求。接下來第一部分文件的剩餘部分將繼續探索完整特徵設定。

命令執行列介面 (Command-Line Interface)

單元測試模組可以透過命令執行列執行測試模組,物件甚至個別的測試方法:

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

你可以通過一個串列與任何模組名稱的組合,完全符合類別與方法的名稱。

測試模組可以根據檔案路徑指定:

python -m unittest tests/test_something.py

這允許你使用 shell 檔案名稱補完功能 (filename completion) 來指定測試模組。給定的檔案路徑必須亦能被當作模組 import。此路徑轉換為模組名稱的方式為移除 '.py' 並將路徑分隔符 (path separator) 轉換成 '.'。 假如你的測試檔案無法被 import 成模組,你應該直接執行該測試檔案。

通過增加 -v 的旗標數,可以在你執行測試時得到更多細節(更高的 verbosity):

python -m unittest -v test_module

若執行時不代任何引數,將執行 Test Discovery(測試探索)

python -m unittest

列出所有命令列選項:

python -m unittest -h

3.2 版更變: 在早期的版本可以個別執行測試方法和不需要模組或是類別。

命令列模式選項

unittest supports these command-line options:

-b, --buffer

Standard output 與 standard error stream 將在測試執行被緩衝 (buffer)。這些輸出在測試通過時被丟棄。若是測試錯誤或失則,這些輸出將會正常地被印出,並且被加入至錯誤訊息中。

-c, --catch

Control-C 測試執行過程中等待正確的測試結果並回報目前為止所有的測試結果。第二個 Control-C 拋出一般例外 KeyboardInterrupt

參照 Signal Handling 針對函式提供的功能。

-f, --failfast

在第一次錯誤或是失敗停止執行測試。

-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_somethingbar_tests.SomeTest.test_foo ,但是不能匹配到 bar_tests.FooTest.test_something

--locals

透過 traceback 顯示本地變數。

3.2 版新加入: 增加命令列模式選項 -b-c-f

3.5 版新加入: 命令列選項 --locals

3.7 版新加入: 命令行选项 -k

對執行所有的專案或是一個子集合測試,命令列模式可以可以被用來做測試探索。

Test Discovery(測試探索)

3.2 版新加入.

單元測試支援簡單的 test discovery(測試探索)。為了相容於測試探索,所有的測試檔案都要是模組或是套件(包含 namespace packages),並能從專案的最上層目錄中 import(代表它們的檔案名稱必須是有效的 identifiers)。

Test discovery(測試探索)實作在 TestLoader.discover(),但也可以被用於命令列模式。基本的命令列模式用法如下:

cd project_directory
python -m unittest discover

備註

python -m unittest 作為捷徑,其功能相當於 python -m unittest discover。假如你想傳遞引數至探索測試的話,一定要明確地加入 discover 子指令。

discover 子指令有以下幾個選項:

-v, --verbose

詳細(verbose)輸出

-s, --start-directory directory

開始尋找的資料夾(預設為 .

-p, --pattern pattern

匹配測試檔案的模式(預設為 test*.py

-t, --top-level-directory directory

專案的最高階層目錄 (defaults to start directory)

-s, -p, 和 -t 選項依照傳遞位置作為引數排序順序。以下兩個命令列被視為等價:

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。

警示

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。

3.4 版更變: 测试发现支持初始目录下的 命名空间包。注意你也需要指定顶层目录(例如:python -m unittest discover -s root/namespace -t root)。

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')

備註

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()

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()__init__() 会被调用一次。

推荐你根据用例所测试的功能将测试用 TestCase 分组。unittest 为此提供了 test suiteunittestTestSuite 类是一个代表。通常情况下,调用 unittest.main() 就能正确地找到并执行这个模块下所有用 TestCase 分组的测试。

然而,如果你需要自定义你的测试套件的话,你可以参考以下方法组织你的测试:

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

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

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

  • 测试模块可以从命令行被独立调用。

  • 更容易在分发的代码中剥离测试代码。

  • 降低没有好理由的情况下修改测试代码以通过测试的诱惑。

  • 测试代码应比被测试代码更少地被修改。

  • 被测试代码可以更容易地被重构。

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

  • 如果测试策略发生了改变,没有必要修改源代码。

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)

備註

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

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

跳过测试与预计的失败

3.1 版新加入.

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

Skipping a test is simply a matter of using the skip() decorator or one of its conditional variants, calling TestCase.skipTest() within a setUp() 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 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))

以下的装饰器和异常实现了跳过测试和预期失败两种功能:

@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)

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 or error. If the test fails or errors in the test function itself (rather than in one of the test fixture methods) then it will be considered a success. If the test passes, it will be considered 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()tearDown() 不会被运行。被跳过的类的 setUpClass()tearDownClass() 不会被运行。被跳过的模组的 setUpModule()tearDownModule() 不会被运行。

Distinguishing test iterations using subtests

3.4 版新加入.

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

例如,以下测试:

class NumbersTest(unittest.TestCase):

    def test_even(self):
        """
        Test that numbers between 0 and 5 are all even.
        """
        for i in range(0, 6):
            with self.subTest(i=i):
                self.assertEqual(i % 2, 0)

可以得到以下输出:

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

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

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

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

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

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 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.

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

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

第一组(用于运行测试的)方法是:

setUp()

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

tearDown()

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

setUpClass()

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

@classmethod
def setUpClass(cls):
    ...

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

3.2 版新加入.

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 版新加入.

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.

3.3 版更變: 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 版新加入.

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 版新加入.

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).

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

3.2 版更變: 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 are (or are not) the same object.

3.1 版新加入.

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

Test that expr is (or is not) None.

3.1 版新加入.

assertIn(member, container, msg=None)
assertNotIn(member, container, msg=None)

Test that member is (or is not) in container.

3.1 版新加入.

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 版新加入.

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)

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

3.2 版更變: Added the exception attribute.

3.3 版更變: 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')

或是:

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

3.1 版新加入: 以方法名``assertRaisesRegexp``添加。

3.2 版更變: Renamed to assertRaisesRegex().

3.3 版更變: 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 版新加入.

3.3 版更變: 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')

或是:

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

3.2 版新加入.

3.3 版更變: 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 that were not blocked by a non-propagating descendent logger.

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 版新加入.

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.

3.2 版更變: 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 版新加入.

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

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

3.1 版新加入: 以方法名``assertRegexpMatches``添加。

3.2 版更變: 方法 assertRegexpMatches() 已被改名为 assertRegex()

3.2 版新加入: assertNotRegex()

3.5 版新加入: assertNotRegexpMatches 这个名字是 assertNotRegex() 的已被弃用的别名。

assertCountEqual(first, second, msg=None)

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

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

3.2 版新加入.

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 版新加入.

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

Method

用作比较

New in

assertMultiLineEqual(a, b)

字符串

3.1

assertSequenceEqual(a, b)

序列

3.1

assertListEqual(a, b)

列表

3.1

assertTupleEqual(a, b)

元组

3.1

assertSetEqual(a, b)

集合

3.1

assertDictEqual(a, b)

字典

3.1

assertMultiLineEqual(first, second, msg=None)

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

3.1 版新加入.

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 版新加入.

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 版新加入.

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 版新加入.

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 版新加入.

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 版新加入.

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 版新加入.

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.

3.1 版更變: 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 版新加入.

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 版新加入.

classmethod addClassCleanup(function, /, *args, **kwargs)

Add a function to be called after tearDownClass() to cleanup resources used during the test class. 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 addClassCleanup() when they are added.

If setUpClass() fails, meaning that tearDownClass() is not called, then any cleanup functions added will still be called.

3.8 版新加入.

classmethod doClassCleanups()

This method is called unconditionally after tearDownClass(), or after setUpClass() if setUpClass() raises an exception.

It is responsible for calling all the cleanup functions added by addClassCleanup(). If you need cleanup functions to be called prior to tearDownClass() then you can call doClassCleanups() yourself.

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

3.8 版新加入.

class unittest.IsolatedAsyncioTestCase(methodName='runTest')

This class provides an API similar to TestCase and also accepts coroutines as test functions.

3.8 版新加入.

coroutine asyncSetUp()

Method called to prepare the test fixture. This is called after setUp(). 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.

coroutine asyncTearDown()

Method called immediately after the test method has been called and the result recorded. This is called before tearDown(). 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 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 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. At the end of the test all the tasks in 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 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.

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 版後已棄用: The fail* aliases listed in the second column have been deprecated.

3.2 版後已棄用: The assert* aliases listed in the third column have been deprecated.

3.2 版後已棄用: assertRegexpMatches and assertRaisesRegexp have been renamed to assertRegex() and assertRaisesRegex().

3.5 版後已棄用: 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 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.

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

3.4 版更變: 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.

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 版新加入.

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.

備註

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.

3.2 版更變: Support for load_tests added.

3.5 版更變: 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.

3.5 版更變: 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 版新加入.

3.4 版更變: Modules that raise SkipTest on import are recorded as skips, not errors.

3.4 版更變: start_dir can be a namespace packages.

3.4 版更變: 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.

3.5 版更變: 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.

testNamePatterns

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

If this attribute is not None (the default), all test methods to be included 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 patterns will have to be converted using * wildcards.

This affects all the loadTestsFrom*() methods.

3.7 版新加入.

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 版新加入.

expectedFailures

A list containing 2-tuples of TestCase instances and strings holding formatted tracebacks. Each tuple represents an expected failure or error 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 版新加入.

failfast

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

3.2 版新加入.

tb_locals

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

3.5 版新加入.

wasSuccessful()

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

3.4 版更變: 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 版新加入.

stopTestRun()

Called once after all tests are executed.

3.1 版新加入.

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 or errors, 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 版新加入.

class unittest.TextTestResult(stream, descriptions, verbosity)

A concrete implementation of TestResult used by the TextTestRunner.

3.2 版新加入: 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.

3.2 版更變: Added the warnings argument.

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

3.5 版更變: 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.

3.1 版更變: The exit parameter was added.

3.2 版更變: The verbosity, failfast, catchbreak, buffer and warnings parameters were added.

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

load_tests Protocol

3.2 版新加入.

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

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

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.

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.

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.

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

unittest.addModuleCleanup(function, /, *args, **kwargs)

Add a function to be called after tearDownModule() to cleanup resources used during the test class. 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 addModuleCleanup() when they are added.

If setUpModule() fails, meaning that tearDownModule() is not called, then any cleanup functions added will still be called.

3.8 版新加入.

unittest.doModuleCleanups()

This function is called unconditionally after tearDownModule(), or after setUpModule() if setUpModule() raises an exception.

It is responsible for calling all the cleanup functions added by addCleanupModule(). If you need cleanup functions to be called prior to tearDownModule() then you can call doModuleCleanups() yourself.

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

3.8 版新加入.

信号处理

3.2 版新加入.

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):
    ...