25.3. "unittest" — 單元測試框架
*******************************

2.1 版新加入.

（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。）

The Python unit testing framework, sometimes referred to as 「PyUnit,
」 is a Python language version of JUnit, by Kent Beck and Erich
Gamma. JUnit is, in turn, a Java version of Kent’s Smalltalk testing
framework.  Each is the de facto standard unit testing framework for
its respective language.

"unittest" supports test automation, sharing of setup and shutdown
code for tests, aggregation of tests into collections, and
independence of the tests from the reporting framework.  The
"unittest" module provides classes that make it easy to support these
qualities for a set of tests.

To achieve this, "unittest" supports some important concepts:

test fixture
   一個 *test fixture* 代表一個或多個測試所需要執行的準備，以及其他相
   關清理行動，可以包括，例如，建立臨時或是代理資料庫，目錄，或是啟動
   一個服務的程序。

test case（測試用例）
   A *test case* is the smallest unit of testing.  It checks for a
   specific response to a particular set of inputs.  "unittest"
   provides a base class, "TestCase", which may be used to create new
   test cases.

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。

The test case and test fixture concepts are supported through the
"TestCase" and "FunctionTestCase" classes; the former should be used
when creating new tests, and the latter can be used when integrating
existing test code with a "unittest"-driven framework. When building
test fixtures using "TestCase", the "setUp()" and "tearDown()" methods
can be overridden to provide initialization and cleanup for the
fixture.  With "FunctionTestCase", existing functions can be passed to
the constructor for these purposes.  When the test is run, the fixture
initialization is run first; if it succeeds, the cleanup method is run
after the test has been executed, regardless of the outcome of the
test.  Each instance of the "TestCase" will only be used to run a
single test method, so a new fixture is created for each test.

Test suites are implemented by the "TestSuite" class.  This class
allows individual tests and test suites to be aggregated; when the
suite is executed, all tests added directly to the suite and in 「
child」 test suites are run.

A test runner is an object that provides a single method, "run()",
which accepts a "TestCase" or "TestSuite" object as a parameter, and
returns a result object.  The class "TestResult" is provided for use
as the result object. "unittest" provides the "TextTestRunner" as an
example test runner which reports test results on the standard error
stream by default.  Alternate runners can be implemented for other
environments (such as graphical environments) without any need to
derive from a specific class.

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。

  unittest2: A backport of new unittest features for Python 2.4-2.6
     Many new features were added to unittest in Python 2.7, including
     test discovery. unittest2 allows you to use these features with
     earlier versions of Python.

  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。

  Nose and pytest
     第三方的單元測試框架，但在撰寫測試時使用更輕量的語法。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。


25.3.1. 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。

The "setUp()" and "tearDown()" methods allow you to define
instructions that will be executed before and after each test method.
They are covered in more detail in the section Organizing test code.

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

Instead of "unittest.main()", there are other ways to run the tests
with a finer level of control, less terse output, and no requirement
to be run from the command line.  For example, the last two lines may
be replaced with:

   suite = unittest.TestLoader().loadTestsFromTestCase(TestStringMethods)
   unittest.TextTestRunner(verbosity=2).run(suite)

Running the revised script from the interpreter or another script
produces the following output:

   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。


25.3.2. 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。

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

列出所有命令列選項：

   python -m unittest -h

2.7 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。


25.3.2.1. 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。

2.7 版新加入: 增加命令列模式選項 "-b" 、 "-c" 與 "-f"。

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
。


25.3.3. Test Discovery（測試探索）
==================================

2.7 版新加入.

Unittest supports simple test discovery. In order to be compatible
with test discovery, all of the test files must be modules or packages
importable from the top-level directory of the project (this means
that their filenames must be valid 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

"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"

As well as being a path it is possible to pass a package name, for
example "myproject.subpackage.test", as the start directory. The
package name you supply will then be imported and its location on the
filesystem will be used as the start directory.

警示: Test discovery loads tests by importing them. Once test
  discovery has found all the test files from the start directory you
  specify it turns the paths into package names to import. For example
  "foo/bar/baz.py" will be imported as "foo.bar.baz".If you have a
  package installed globally and attempt test discovery on a different
  copy of the package then the import *could* happen from the wrong
  place. If this happens test discovery will warn you and exit.If you
  supply the start directory as a package name rather than a path to a
  directory then discover assumes that whichever location it imports
  from is the location you intended, so you will not get the warning.

Test modules and packages can customize test loading and discovery by
through the load_tests protocol.


25.3.4. Organizing test code
============================

The basic building blocks of unit testing are *test cases* — single
scenarios that must be set up and checked for correctness.  In
"unittest", test cases are represented by instances of "unittest"’s
"TestCase" class. To make your own test cases you must write
subclasses of "TestCase", or use "FunctionTestCase".

An instance of a "TestCase"-derived class is an object that can
completely run a single test method, together with optional set-up and
tidy-up code.

The testing code of a "TestCase" instance should be entirely self
contained, such that it can be run either in isolation or in arbitrary
combination with any number of other test cases.

The simplest "TestCase" subclass will simply override the "runTest()"
method in order to perform specific testing code:

   import unittest

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

Note that in order to test something, we use one of the "assert*()"
methods provided by the "TestCase" base class.  If the test fails, an
exception will be raised, and "unittest" will identify the test case
as a *failure*.  Any other exceptions will be treated as *errors*.
This helps you identify where the problem is: *failures* are caused by
incorrect results - a 5 where you expected a 6. *Errors* are caused by
incorrect code - e.g., a "TypeError" caused by an incorrect function
call.

The way to run a test case will be described later.  For now, note
that to construct an instance of such a test case, we call its
constructor without arguments:

   testCase = DefaultWidgetSizeTestCase()

Now, such test cases can be numerous, and their set-up can be
repetitive.  In the above case, constructing a "Widget" in each of 100
Widget test case subclasses would mean unsightly duplication.

Luckily, we can factor out such set-up code by implementing a method
called "setUp()", which the testing framework will automatically call
for us when we run the test:

   import unittest

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

   class DefaultWidgetSizeTestCase(SimpleWidgetTestCase):
       def runTest(self):
           self.assertEqual(self.widget.size(), (50,50),
                            'incorrect default size')

   class WidgetResizeTestCase(SimpleWidgetTestCase):
       def runTest(self):
           self.widget.resize(100,150)
           self.assertEqual(self.widget.size(), (100,150),
                            'wrong size after resize')

If the "setUp()" method raises an exception while the test is running,
the framework will consider the test to have suffered an error, and
the "runTest()" method will not be executed.

Similarly, we can provide a "tearDown()" method that tidies up after
the "runTest()" method has been run:

   import unittest

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

       def tearDown(self):
           self.widget.dispose()
           self.widget = None

If "setUp()" succeeded, the "tearDown()" method will be run whether
"runTest()" succeeded or not.

Such a working environment for the testing code is called a *fixture*.

Often, many small test cases will use the same fixture.  In this case,
we would end up subclassing "SimpleWidgetTestCase" into many small
one-method classes such as "DefaultWidgetSizeTestCase".  This is time-
consuming and discouraging, so in the same vein as JUnit, "unittest"
provides a simpler mechanism:

   import unittest

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

       def tearDown(self):
           self.widget.dispose()
           self.widget = None

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

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

Here we have not provided a "runTest()" method, but have instead
provided two different test methods.  Class instances will now each
run one of the "test_*()" methods, with "self.widget" created and
destroyed separately for each instance.  When creating an instance we
must specify the test method it is to run.  We do this by passing the
method name in the constructor:

   defaultSizeTestCase = WidgetTestCase('test_default_size')
   resizeTestCase = WidgetTestCase('test_resize')

Test case instances are grouped together according to the features
they test. "unittest" provides a mechanism for this: the *test suite*,
represented by "unittest"’s "TestSuite" class:

   widgetTestSuite = unittest.TestSuite()
   widgetTestSuite.addTest(WidgetTestCase('test_default_size'))
   widgetTestSuite.addTest(WidgetTestCase('test_resize'))

For the ease of running tests, as we will see later, it is a good idea
to provide in each test module a callable object that returns a pre-
built test suite:

   def suite():
       suite = unittest.TestSuite()
       suite.addTest(WidgetTestCase('test_default_size'))
       suite.addTest(WidgetTestCase('test_resize'))
       return suite

or even:

   def suite():
       tests = ['test_default_size', 'test_resize']

       return unittest.TestSuite(map(WidgetTestCase, tests))

Since it is a common pattern to create a "TestCase" subclass with many
similarly named test functions, "unittest" provides a "TestLoader"
class that can be used to automate the process of creating a test
suite and populating it with individual tests. For example,

   suite = unittest.TestLoader().loadTestsFromTestCase(WidgetTestCase)

will create a test suite that will run
"WidgetTestCase.test_default_size()" and "WidgetTestCase.test_resize".
"TestLoader" uses the "'test'" method name prefix to identify test
methods automatically.

Note that the order in which the various test cases will be run is
determined by sorting the test function names with respect to the
built-in ordering for strings.

Often it is desirable to group suites of test cases together, so as to
run tests for the whole system at once.  This is easy, since
"TestSuite" instances can be added to a "TestSuite" just as "TestCase"
instances can be added to a "TestSuite":

   suite1 = module1.TheTestSuite()
   suite2 = module2.TheTestSuite()
   alltests = unittest.TestSuite([suite1, suite2])

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

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

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

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

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

* Tested code can be refactored more easily.

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

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


25.3.5. Re-using old test code
==============================

Some users will find that they have existing test code that they would
like to run from "unittest", without converting every old test
function to a "TestCase" subclass.

For this reason, "unittest" provides a "FunctionTestCase" class. This
subclass of "TestCase" can be used to wrap an existing test function.
Set-up and tear-down functions can also be provided.

Given the following test function:

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

one can create an equivalent test case instance as follows:

   testcase = unittest.FunctionTestCase(testSomething)

If there are additional set-up and tear-down methods that should be
called as part of the test case’s operation, they can also be provided
like so:

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

To make migrating existing test suites easier, "unittest" supports
tests raising "AssertionError" to indicate test failure. However, it
is recommended that you use the explicit "TestCase.fail*()" and
"TestCase.assert*()" methods instead, as future versions of "unittest"
may treat "AssertionError" differently.

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

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


25.3.6. Skipping tests and expected failures
============================================

2.7 版新加入.

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

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

Basic skipping looks like this:

   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

This is the output of running the example above in verbose mode:

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

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

   OK (skipped=3)

Classes can be skipped just like methods:

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

"TestCase.setUp()" can also skip the test.  This is useful when a
resource that needs to be set up is not available.

Expected failures use the "expectedFailure()" decorator.

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

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

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

The following decorators implement test skipping and expected
failures:

unittest.skip(reason)

   Unconditionally skip the decorated test.  *reason* should describe
   why the test is being skipped.

unittest.skipIf(condition, reason)

   Skip the decorated test if *condition* is true.

unittest.skipUnless(condition, reason)

   Skip the decorated test unless *condition* is true.

unittest.expectedFailure()

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

exception unittest.SkipTest(reason)

   This exception is raised to skip a test.

   Usually you can use "TestCase.skipTest()" or one of the skipping
   decorators instead of raising this directly.

Skipped tests will not have "setUp()" or "tearDown()" run around them.
Skipped classes will not have "setUpClass()" or "tearDownClass()" run.


25.3.7. Classes and functions
=============================

This section describes in depth the API of "unittest".


25.3.7.1. Test cases
--------------------

class unittest.TestCase(methodName='runTest')

   Instances of the "TestCase" class represent the smallest testable
   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 test, 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 test method: the
   method named *methodName*.  If you remember, we had an earlier
   example that went something like this:

      def suite():
          suite = unittest.TestSuite()
          suite.addTest(WidgetTestCase('test_default_size'))
          suite.addTest(WidgetTestCase('test_resize'))
          return suite

   Here, we create two instances of "WidgetTestCase", each of which
   runs a single test.

   *methodName* defaults to "runTest()".

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

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

   setUp()

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

   tearDown()

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

   setUpClass()

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

         @classmethod
         def setUpClass(cls):
             ...

      See Class and Module Fixtures for more details.

      2.7 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):
             ...

      See Class and Module Fixtures for more details.

      2.7 版新加入.

   run(result=None)

      Run the test, collecting the result into the test result 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 not
      returned to "run()"』s caller.

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

   skipTest(reason)

      Calling this during a test method or "setUp()" skips the current
      test.  See Skipping tests and expected failures for more
      information.

      2.7 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"                      | 2.7             |
   +-------------------------------------------+-------------------------------+-----------------+
   | "assertIsNot(a, b)"                       | "a is not b"                  | 2.7             |
   +-------------------------------------------+-------------------------------+-----------------+
   | "assertIsNone(x)"                         | "x is None"                   | 2.7             |
   +-------------------------------------------+-------------------------------+-----------------+
   | "assertIsNotNone(x)"                      | "x is not None"               | 2.7             |
   +-------------------------------------------+-------------------------------+-----------------+
   | "assertIn(a, b)"                          | "a in b"                      | 2.7             |
   +-------------------------------------------+-------------------------------+-----------------+
   | "assertNotIn(a, b)"                       | "a not in b"                  | 2.7             |
   +-------------------------------------------+-------------------------------+-----------------+
   | "assertIsInstance(a, b)"                  | "isinstance(a, b)"            | 2.7             |
   +-------------------------------------------+-------------------------------+-----------------+
   | "assertNotIsInstance(a, b)"               | "not isinstance(a, b)"        | 2.7             |
   +-------------------------------------------+-------------------------------+-----------------+

   All the assert methods (except "assertRaises()",
   "assertRaisesRegexp()") accept a *msg* argument that, if specified,
   is used as the error message on failure (see also "longMessage").

   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 unicode 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).

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

   assertNotEqual(first, second, msg=None)

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

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

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

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

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

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

      2.7 版新加入.

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

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

      2.7 版新加入.

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

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

      2.7 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)".

      2.7 版新加入.

   It is also possible to check that exceptions and warnings are
   raised using the following methods:

   +-----------------------------------------------------------+----------------------------------------+--------------+
   | Method                                                    | Checks that                            | New in       |
   +===========================================================+========================================+==============+
   | "assertRaises(exc, fun, *args, **kwds)"                   | "fun(*args, **kwds)" raises *exc*      |              |
   +-----------------------------------------------------------+----------------------------------------+--------------+
   | "assertRaisesRegexp(exc, r, fun, *args, **kwds)"          | "fun(*args, **kwds)" raises *exc* and  | 2.7          |
   |                                                           | the message matches regex *r*          |              |
   +-----------------------------------------------------------+----------------------------------------+--------------+

   assertRaises(exception, callable, *args, **kwds)
   assertRaises(exception)

      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* argument is given, returns a context
      manager so that the code under test can be written inline rather
      than as a function:

         with self.assertRaises(SomeException):
             do_something()

      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)

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

   assertRaisesRegexp(exception, regexp, callable, *args, **kwds)
   assertRaisesRegexp(exception, regexp)

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

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

      或是：

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

      2.7 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"                          | 2.7            |
   +-----------------------------------------+----------------------------------+----------------+
   | "assertGreaterEqual(a, b)"              | "a >= b"                         | 2.7            |
   +-----------------------------------------+----------------------------------+----------------+
   | "assertLess(a, b)"                      | "a < b"                          | 2.7            |
   +-----------------------------------------+----------------------------------+----------------+
   | "assertLessEqual(a, b)"                 | "a <= b"                         | 2.7            |
   +-----------------------------------------+----------------------------------+----------------+
   | "assertRegexpMatches(s, r)"             | "r.search(s)"                    | 2.7            |
   +-----------------------------------------+----------------------------------+----------------+
   | "assertNotRegexpMatches(s, r)"          | "not r.search(s)"                | 2.7            |
   +-----------------------------------------+----------------------------------+----------------+
   | "assertItemsEqual(a, b)"                | sorted(a) == sorted(b) and works | 2.7            |
   |                                         | with unhashable objs             |                |
   +-----------------------------------------+----------------------------------+----------------+
   | "assertDictContainsSubset(a, b)"        | all the key/value pairs in *a*   | 2.7            |
   |                                         | exist in *b*                     |                |
   +-----------------------------------------+----------------------------------+----------------+

   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".

      2.7 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"

      2.7 版新加入.

   assertRegexpMatches(text, regexp, msg=None)

      Test that a *regexp* search matches *text*.  In case of failure,
      the error message will include the pattern and the *text* (or
      the pattern and the part of *text* that unexpectedly matched).
      *regexp* may be a regular expression object or a string
      containing a regular expression suitable for use by
      "re.search()".

      2.7 版新加入.

   assertNotRegexpMatches(text, regexp, msg=None)

      Verifies that a *regexp* search does not match *text*.  Fails
      with an error message including the pattern and the part of
      *text* that matches.  *regexp* may be a regular expression
      object or a string containing a regular expression suitable for
      use by "re.search()".

      2.7 版新加入.

   assertItemsEqual(actual, expected, msg=None)

      Test that sequence *expected* contains the same elements as
      *actual*, 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 *actual* and
      *expected*. It verifies if each element has the same count in
      both sequences. It is the equivalent of
      "assertEqual(sorted(expected), sorted(actual))" but it works
      with sequences of unhashable objects as well.

      In Python 3, this method is named "assertCountEqual".

      2.7 版新加入.

   assertDictContainsSubset(expected, actual, msg=None)

      Tests whether the key/value pairs in dictionary *actual* are a
      superset of those in *expected*.  If not, an error message
      listing the missing keys and mismatched values is generated.

      2.7 版新加入.

      3.2 版後已棄用.

   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.

      2.7 版新加入.

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

   +-------------------------------------------+-------------------------------+----------------+
   | Method                                    | Used to compare               | New in         |
   +===========================================+===============================+================+
   | "assertMultiLineEqual(a, b)"              | strings                       | 2.7            |
   +-------------------------------------------+-------------------------------+----------------+
   | "assertSequenceEqual(a, b)"               | sequences                     | 2.7            |
   +-------------------------------------------+-------------------------------+----------------+
   | "assertListEqual(a, b)"                   | lists                         | 2.7            |
   +-------------------------------------------+-------------------------------+----------------+
   | "assertTupleEqual(a, b)"                  | tuples                        | 2.7            |
   +-------------------------------------------+-------------------------------+----------------+
   | "assertSetEqual(a, b)"                    | sets or frozensets            | 2.7            |
   +-------------------------------------------+-------------------------------+----------------+
   | "assertDictEqual(a, b)"                   | dicts                         | 2.7            |
   +-------------------------------------------+-------------------------------+----------------+

   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 Unicode strings with
      "assertEqual()".

      2.7 版新加入.

   assertSequenceEqual(seq1, seq2, msg=None, seq_type=None)

      Tests that two sequences are equal.  If a *seq_type* is
      supplied, both *seq1* and *seq2* 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()".

      2.7 版新加入.

   assertListEqual(list1, list2, msg=None)
   assertTupleEqual(tuple1, tuple2, 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()".

      2.7 版新加入.

   assertSetEqual(set1, set2, 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 *set1* or *set2* does not have a
      "set.difference()" method.

      2.7 版新加入.

   assertDictEqual(expected, actual, 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()".

      2.7 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

      If set to "True" then any explicit failure message you pass in
      to the assert methods will be appended to the end of the normal
      failure message.  The normal messages contain useful information
      about the objects involved, for example the message from
      assertEqual shows you the repr of the two unequal objects.
      Setting this attribute to "True" allows you to have a custom
      error message in addition to the normal one.

      This attribute defaults to "False", meaning that a custom
      message passed to an assert method will silence the normal
      message.

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

      2.7 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.

      2.7 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".

   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.

      2.7 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.

      2.7 版新加入.

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.


25.3.7.1.1. Deprecated aliases
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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

   +--------------------------------+---------------------------------+
   | Method Name                    | Deprecated alias(es)            |
   +================================+=================================+
   | "assertEqual()"                | failUnlessEqual, assertEquals   |
   +--------------------------------+---------------------------------+
   | "assertNotEqual()"             | failIfEqual                     |
   +--------------------------------+---------------------------------+
   | "assertTrue()"                 | failUnless, assert_             |
   +--------------------------------+---------------------------------+
   | "assertFalse()"                | failIf                          |
   +--------------------------------+---------------------------------+
   | "assertRaises()"               | failUnlessRaises                |
   +--------------------------------+---------------------------------+
   | "assertAlmostEqual()"          | failUnlessAlmostEqual           |
   +--------------------------------+---------------------------------+
   | "assertNotAlmostEqual()"       | failIfAlmostEqual               |
   +--------------------------------+---------------------------------+

   2.7 版後已棄用: the aliases listed in the second column


25.3.7.2. Grouping tests
------------------------

class unittest.TestSuite(tests=())

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

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

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

   addTest(test)

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

   addTests(tests)

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

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

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

   run(result)

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

   debug()

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

   countTestCases()

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

   __iter__()

      Tests grouped by a "TestSuite" are always accessed by iteration.
      Subclasses can lazily provide tests by overriding "__iter__()".
      Note that this method maybe called several times on a single
      suite (for example when counting tests or comparing for
      equality) so the tests returned must be the same for repeated
      iterations.

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

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


25.3.7.3. Loading and running tests
-----------------------------------

class unittest.TestLoader

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

   "TestLoader" objects have the following methods:

   loadTestsFromTestCase(testCaseClass)

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

   loadTestsFromModule(module)

      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.

      2.7 版更變: Support for "load_tests" added.

   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*.

   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 a test package name (directory with "__init__.py") matches
      the pattern then the package will be checked for a "load_tests"
      function. If this exists then it will be called with *loader*,
      *tests*, *pattern*.

      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.

      2.7 版新加入.

   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. The
      default value is the built-in "cmp()" function; the attribute
      can also be set to "None" to disable the sort.

   suiteClass

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

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

class unittest.TestResult

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

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

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

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

   errors

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

      2.2 版更變: Contains formatted tracebacks instead of
      "sys.exc_info()" results.

   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.

      2.2 版更變: Contains formatted tracebacks instead of
      "sys.exc_info()" results.

   skipped

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

      2.7 版新加入.

   expectedFailures

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

   unexpectedSuccesses

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

   shouldStop

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

   testsRun

      The total number of tests run so far.

   buffer

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

      2.7 版新加入.

   failfast

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

      2.7 版新加入.

   wasSuccessful()

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

   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.

      2.7 版新加入.

   stopTestRun()

      Called once after all tests are executed.

      2.7 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, 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.

class unittest.TextTestResult(stream, descriptions, verbosity)

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

   2.7 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=sys.stderr, descriptions=True, verbosity=1, failfast=False, buffer=False, resultclass=None)

   A basic test runner implementation which prints results on standard
   error. It has a few configurable parameters, but is essentially
   very simple.  Graphical applications which run test suites should
   provide alternate implementations.

   _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

unittest.main([module[, defaultTest[, argv[, testRunner[, testLoader[, exit[, verbosity[, failfast[, catchbreak[, buffer]]]]]]]]]])

   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 the name of the test 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.

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

   2.7 版更變: The *exit*, *verbosity*, *failfast*, *catchbreak* and
   *buffer* parameters were added.


25.3.7.3.1. load_tests Protocol
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

2.7 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, 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, either from the command line or by calling
"TestLoader.discover()", with a pattern that matches a package name
then the package "__init__.py" will be checked for "load_tests".

備註: The default pattern is "'test*.py'". This matches all Python
  files that start with "'test'" but *won’t* match any test
  directories.A pattern like "'test*'" will match test packages as
  well as modules.

If the package "__init__.py" defines "load_tests" then it will be
called and discovery not continued into the package. "load_tests" 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


25.3.8. 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.


25.3.8.1. setUpClass and tearDownClass
--------------------------------------

These must be implemented as class methods:

   import unittest

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

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

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

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


25.3.8.2. setUpModule and tearDownModule
----------------------------------------

These should be implemented as functions:

   def setUpModule():
       createConnection()

   def tearDownModule():
       closeConnection()

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


25.3.9. Signal Handling
=======================

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.

   2.7 版新加入.

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.

   2.7 版新加入.

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.

   2.7 版新加入.

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):
          ...

   2.7 版新加入.
