"unittest" --- Unit testing framework
*************************************

**Source code:** Lib/unittest/__init__.py

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

(If you are already familiar with the basic concepts of testing, you
might want to skip to the list of assert methods.)

The "unittest" unit testing framework was originally inspired by JUnit
and has a similar flavor as major unit testing frameworks in other
languages.  It 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.

To achieve this, "unittest" supports some important concepts in an
object-oriented way:

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

test case
   A *test case* is the individual 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
   A *test suite* is a collection of test cases, test suites, or both.
   It is used to aggregate tests that should be executed together.

test runner
   A *test runner* is a component which orchestrates the execution of
   tests and provides the outcome to the user.  The runner may use a
   graphical interface, a textual interface, or return a special value
   to indicate the results of executing the tests.

See also:

  Module "doctest"
     Another test-support module with a very different flavor.

  Simple Smalltalk Testing: With Patterns
     Kent Beck's original paper on testing frameworks using the
     pattern shared by "unittest".

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

  The Python Testing Tools Taxonomy
     An extensive list of Python testing tools including functional
     testing frameworks and mock object libraries.

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

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


Basic example
=============

The "unittest" module provides a rich set of tools for constructing
and running tests.  This section demonstrates that a small subset of
the tools suffice to meet the needs of most users.

Here is a short script to test three string methods:

   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()

A test case is created by subclassing "unittest.TestCase".  The three
individual tests are defined with methods whose names start with the
letters "test".  This naming convention informs the test runner about
which methods represent tests.

The crux of each test is a call to "assertEqual()" to check for an
expected result; "assertTrue()" or "assertFalse()" to verify a
condition; or "assertRaises()" to verify that a specific exception
gets raised.  These methods are used instead of the "assert" statement
so the test runner can accumulate all test results and produce a
report.

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.

The final block shows a simple way to run the tests. "unittest.main()"
provides a command-line interface to the test script.  When run from
the command line, the above script produces an output that looks like
this:

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

   OK

Passing the "-v" option to your test script will instruct
"unittest.main()" to enable a higher level of verbosity, and produce
the following output:

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

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

   OK

The above examples show the most commonly used "unittest" features
which are sufficient to meet many everyday testing needs.  The
remainder of the documentation explores the full feature set from
first principles.

Changed in version 3.11: The behavior of returning a value from a test
method (other than the default "None" value), is now deprecated.


Command-Line Interface
======================

The unittest module can be used from the command line to run tests
from modules, classes or even individual test methods:

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

You can pass in a list with any combination of module names, and fully
qualified class or method names.

Test modules can be specified by file path as well:

   python -m unittest tests/test_something.py

This allows you to use the shell filename completion to specify the
test module. The file specified must still be importable as a module.
The path is converted to a module name by removing the '.py' and
converting path separators into '.'. If you want to execute a test
file that isn't importable as a module you should execute the file
directly instead.

You can run tests with more detail (higher verbosity) by passing in
the -v flag:

   python -m unittest -v test_module

When executed without arguments Test Discovery is started:

   python -m unittest

For a list of all the command-line options:

   python -m unittest -h

Changed in version 3.2: In earlier versions it was only possible to
run individual test methods and not modules or classes.


Command-line options
--------------------

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

-b, --buffer

   The standard output and standard error streams are buffered during
   the test run. Output during a passing test is discarded. Output is
   echoed normally on test fail or error and is added to the failure
   messages.

-c, --catch

   "Control"-"C" during the test run waits for the current test to end
   and then reports all the results so far. A second "Control"-"C"
   raises the normal "KeyboardInterrupt" exception.

   See Signal Handling for the functions that provide this
   functionality.

-f, --failfast

   Stop the test run on the first error or failure.

-k

   Only run test methods and classes that match the pattern or
   substring. This option may be used multiple times, in which case
   all test cases that match any of the given patterns are included.

   Patterns that contain a wildcard character ("*") are matched
   against the test name using "fnmatch.fnmatchcase()"; otherwise
   simple case-sensitive substring matching is used.

   Patterns are matched against the fully qualified test method name
   as imported by the test loader.

   For example, "-k foo" matches "foo_tests.SomeTest.test_something",
   "bar_tests.SomeTest.test_foo", but not
   "bar_tests.FooTest.test_something".

--locals

   Show local variables in tracebacks.

--durations N

   Show the N slowest test cases (N=0 for all).

Added in version 3.2: The command-line options "-b", "-c" and "-f"
were added.

Added in version 3.5: The command-line option "--locals".

Added in version 3.7: The command-line option "-k".

Added in version 3.12: The command-line option "--durations".

The command line can also be used for test discovery, for running all
of the tests in a project or just a subset.


Test Discovery
==============

Added in version 3.2.

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 is implemented in "TestLoader.discover()", but can also
be used from the command line. The basic command-line usage is:

   cd project_directory
   python -m unittest discover

Note:

  As a shortcut, "python -m unittest" is the equivalent of "python -m
  unittest discover". If you want to pass arguments to test discovery
  the "discover" sub-command must be used explicitly.

The "discover" sub-command has the following options:

-v, --verbose

   Verbose output

-s, --start-directory directory

   Directory to start discovery ("." default)

-p, --pattern pattern

   Pattern to match test files ("test*.py" default)

-t, --top-level-directory directory

   Top level directory of project (defaults to start directory)

The "-s", "-p", and "-t" options can be passed in as positional
arguments in that order. The following two command lines are
equivalent:

   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.

Caution:

  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.

Changed in version 3.4: Test discovery supports *namespace packages*
for the start directory. Note that you need to specify the top level
directory too (e.g. "python -m unittest discover -s root/namespace -t
root").

Changed in version 3.11: "unittest" dropped the *namespace packages*
support in Python 3.11. It has been broken since Python 3.7. Start
directory and subdirectories containing tests must be regular package
that have "__init__.py" file.Directories containing start directory
still can be a namespace package. In this case, you need to specify
start directory as dotted package name, and target directory
explicitly. For example:

   # proj/  <-- current directory
   #   namespace/
   #     mypkg/
   #       __init__.py
   #       test_mypkg.py

   python -m unittest discover -s namespace.mypkg -t .


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 "unittest.TestCase"
instances. To make your own test cases you must write subclasses of
"TestCase" or use "FunctionTestCase".

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 implement a test method
(i.e. a method whose name starts with "test") in order to perform
specific testing code:

   import unittest

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

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 with an explanatory message, and "unittest"
will identify the test case as a *failure*.  Any other exceptions will
be treated as *errors*.

Tests can be numerous, and their set-up can be repetitive.  Luckily,
we can factor out set-up code by implementing a method called
"setUp()", which the testing framework will automatically call for
every single test we run:

   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')

Note:

  The order in which the various tests will be run is determined by
  sorting the test method names with respect to the built-in ordering
  for strings.

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 test method will not be executed.

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

   import unittest

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

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

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

Such a working environment for the testing code is called a *test
fixture*.  A new TestCase instance is created as a unique test fixture
used to execute each individual test method.  Thus "setUp()",
"tearDown()", and "TestCase.__init__()" will be called once per test.

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

However, should you want to customize the building of your test suite,
you can do it yourself:

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

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

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

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

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

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

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

* Tested code can be refactored more easily.

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

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


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, with
optional set-up and tear-down methods:

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

Note:

  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.


Skipping tests and expected failures
====================================

Added in version 3.1.

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, calling "TestCase.skipTest()"
within a "setUp()" or test method, or raising "SkipTest" directly.

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

       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

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

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

   ----------------------------------------------------------------------
   Ran 4 tests in 0.005s

   OK (skipped=4)

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 and exception 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 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)

   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.
Skipped modules will not have "setUpModule()" or "tearDownModule()"
run.


Distinguishing test iterations using subtests
=============================================

Added in version 3.4.

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.

For example, the following test:

   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)

will produce the following output:

   ======================================================================
   FAIL: test_even (__main__.NumbersTest.test_even) (i=1)
   Test that numbers between 0 and 5 are all even.
   ----------------------------------------------------------------------
   Traceback (most recent call last):
     File "subtests.py", line 11, in test_even
       self.assertEqual(i % 2, 0)
       ^^^^^^^^^^^^^^^^^^^^^^^^^^
   AssertionError: 1 != 0

   ======================================================================
   FAIL: test_even (__main__.NumbersTest.test_even) (i=3)
   Test that numbers between 0 and 5 are all even.
   ----------------------------------------------------------------------
   Traceback (most recent call last):
     File "subtests.py", line 11, in test_even
       self.assertEqual(i % 2, 0)
       ^^^^^^^^^^^^^^^^^^^^^^^^^^
   AssertionError: 1 != 0

   ======================================================================
   FAIL: test_even (__main__.NumbersTest.test_even) (i=5)
   Test that numbers between 0 and 5 are all even.
   ----------------------------------------------------------------------
   Traceback (most recent call last):
     File "subtests.py", line 11, in test_even
       self.assertEqual(i % 2, 0)
       ^^^^^^^^^^^^^^^^^^^^^^^^^^
   AssertionError: 1 != 0

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

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


Classes and functions
=====================

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


Test cases
----------

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.

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

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

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

   setUp()

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

   tearDown()

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

   setUpClass()

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

         @classmethod
         def setUpClass(cls):
             ...

      See Class and Module Fixtures for more details.

      Added in version 3.2.

   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.

      Added in version 3.2.

   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.

      Changed in version 3.3: 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 Skipping tests and expected failures for more
      information.

      Added in version 3.1.

   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.

      See Distinguishing test iterations using subtests for more
      information.

      Added in version 3.4.

   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).

      Changed in version 3.1: Added the automatic calling of type-
      specific equality function.

      Changed in version 3.2: "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.

      Added in version 3.1.

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

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

      Added in version 3.1.

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

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

      Added in version 3.1.

   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)".

      Added in version 3.2.

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

   +-----------------------------------------------------------+----------------------------------------+--------------+
   | Method                                                    | Checks that                            | New in       |
   |===========================================================|========================================|==============|
   | "assertRaises(exc, fun, *args, **kwds)"                   | "fun(*args, **kwds)" raises *exc*      |              |
   +-----------------------------------------------------------+----------------------------------------+--------------+
   | "assertRaisesRegex(exc, r, fun, *args, **kwds)"           | "fun(*args, **kwds)" raises *exc* and  | 3.1          |
   |                                                           | the message matches regex *r*          |              |
   +-----------------------------------------------------------+----------------------------------------+--------------+
   | "assertWarns(warn, fun, *args, **kwds)"                   | "fun(*args, **kwds)" raises *warn*     | 3.2          |
   +-----------------------------------------------------------+----------------------------------------+--------------+
   | "assertWarnsRegex(warn, r, fun, *args, **kwds)"           | "fun(*args, **kwds)" raises *warn* and | 3.2          |
   |                                                           | the message matches regex *r*          |              |
   +-----------------------------------------------------------+----------------------------------------+--------------+
   | "assertLogs(logger, level)"                               | The "with" block logs on *logger* with | 3.4          |
   |                                                           | minimum *level*                        |              |
   +-----------------------------------------------------------+----------------------------------------+--------------+
   | "assertNoLogs(logger, level)"                             | The "with" block does not log on       | 3.10         |
   |                                                           | *logger* with minimum *level*          |              |
   +-----------------------------------------------------------+----------------------------------------+--------------+

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

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

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

         with self.assertRaises(SomeException):
             do_something()

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

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

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

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

      Changed in version 3.1: Added the ability to use
      "assertRaises()" as a context manager.

      Changed in version 3.2: Added the "exception" attribute.

      Changed in version 3.3: 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')

      or:

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

      Added in version 3.1: Added under the name "assertRaisesRegexp".

      Changed in version 3.2: Renamed to "assertRaisesRegex()".

      Changed in version 3.3: 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.

      Added in version 3.2.

      Changed in version 3.3: 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')

      or:

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

      Added in version 3.2.

      Changed in version 3.3: 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.

      Example:

         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'])

      Added in version 3.4.

   assertNoLogs(logger=None, level=None)

      A context manager to test that no messages are logged on the
      *logger* or one of its children, with at least the given
      *level*.

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

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

      Unlike "assertLogs()", nothing will be returned by the context
      manager.

      Added in version 3.10.

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

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

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

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

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

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

      Changed in version 3.2: "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"

      Added in version 3.1.

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

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

      Added in version 3.1: Added under the name
      "assertRegexpMatches".

      Changed in version 3.2: The method "assertRegexpMatches()" has
      been renamed to "assertRegex()".

      Added in version 3.2: "assertNotRegex()".

   assertCountEqual(first, second, msg=None)

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

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

      Added in version 3.2.

   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.

      Added in version 3.1.

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

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

   assertMultiLineEqual(first, second, msg=None)

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

      Added in version 3.1.

   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()".

      Added in version 3.1.

   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()".

      Added in version 3.1.

   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
      "difference()" method.

      Added in version 3.1.

   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()".

      Added in version 3.1.

   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.

      Added in version 3.1.

   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.

      Added in version 3.2.

   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".

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

   addCleanup(function, /, *args, **kwargs)

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

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

      Added in version 3.1.

   enterContext(cm)

      Enter the supplied *context manager*.  If successful, also add
      its "__exit__()" method as a cleanup function by "addCleanup()"
      and return the result of the "__enter__()" method.

      Added in version 3.11.

   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.

      Added in version 3.1.

   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 (last-in,
      first-out)). 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.

      Added in version 3.8.

   classmethod enterClassContext(cm)

      Enter the supplied *context manager*.  If successful, also add
      its "__exit__()" method as a cleanup function by
      "addClassCleanup()" and return the result of the "__enter__()"
      method.

      Added in version 3.11.

   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.

      Added in version 3.8.

class unittest.IsolatedAsyncioTestCase(methodName='runTest')

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

   Added in version 3.8.

   loop_factory

      The *loop_factory* passed to "asyncio.Runner". Override in
      subclasses with "asyncio.EventLoop" to avoid using the asyncio
      policy system.

      Added in version 3.13.

   async asyncSetUp()

      Method called to prepare the test fixture. This is called after
      "TestCase.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.

   async 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.

   async enterAsyncContext(cm)

      Enter the supplied *asynchronous context manager*.  If
      successful, also add its "__aexit__()" method as a cleanup
      function by "addAsyncCleanup()" and return the result of the
      "__aenter__()" method.

      Added in version 3.11.

   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.


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.

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

      Changed in version 3.4: 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 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.

      Added in version 3.5.

   "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.

      Note:

        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".

      Changed in version 3.2: Support for "load_tests" added.

      Changed in version 3.5: Support for a keyword-only argument
      *pattern* has been added.

      Changed in version 3.12: The undocumented and unofficial
      *use_load_tests* parameter has been removed.

   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*.

      Changed in version 3.5: 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 *top_level_dir* 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 internally, and used as a default to
      any nested calls to "discover()". That is, if a package's
      "load_tests" calls "loader.discover()", it does not need to pass
      this argument.

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

      Added in version 3.2.

      Changed in version 3.4: Modules that raise "SkipTest" on import
      are recorded as skips, not errors.

      Changed in version 3.4: *start_dir* can be a *namespace
      packages*.

      Changed in version 3.4: 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.

      Changed in version 3.5: 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.

      Changed in version 3.11: *start_dir* can not be a *namespace
      packages*. It has been broken since Python 3.7 and Python 3.11
      officially remove it.

      Changed in version 3.13: *top_level_dir* is only stored for the
      duration of *discover* call.

   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 "-k"
      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 "-k"
      option, simple substring patterns will have to be converted
      using "*" wildcards.

      This affects all the "loadTestsFrom*" methods.

      Added in version 3.7.

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 assert* methods.

   skipped

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

      Added in version 3.1.

   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.

   collectedDurations

      A list containing 2-tuples of test case names and floats
      representing the elapsed time of each test which was run.

      Added in version 3.12.

   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.

      Added in version 3.2.

   failfast

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

      Added in version 3.2.

   tb_locals

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

      Added in version 3.5.

   wasSuccessful()

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

      Changed in version 3.4: 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.

      Added in version 3.1.

   stopTestRun()

      Called once after all tests are executed.

      Added in version 3.1.

   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.

      Added in version 3.4.

   addDuration(test, elapsed)

      Called when the test case finishes.  *elapsed* is the time
      represented in seconds, and it includes the execution of cleanup
      functions.

      Added in version 3.12.

class unittest.TextTestResult(stream, descriptions, verbosity, *, durations=None)

   A concrete implementation of "TestResult" used by the
   "TextTestRunner". Subclasses should accept "**kwargs" to ensure
   compatibility as the interface changes.

   Added in version 3.2.

   Changed in version 3.12: Added the *durations* keyword parameter.

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, durations=None)

   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.  This behavior can be
   overridden using Python's "-Wd" or "-Wa" options (see Warning
   control) and leaving *warnings* to "None".

   Changed in version 3.2: Added the *warnings* parameter.

   Changed in version 3.2: The default stream is set to "sys.stderr"
   at instantiation time rather than import time.

   Changed in version 3.5: Added the *tb_locals* parameter.

   Changed in version 3.12: Added the *durations* 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 (0) or failure
   (1) of the tests run. An exit code of 5 indicates that no tests
   were run or skipped.

   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" returns an object with the "result" attribute that
   contains the result of the tests run as a "unittest.TestResult".

   Changed in version 3.1: The *exit* parameter was added.

   Changed in version 3.2: The *verbosity*, *failfast*, *catchbreak*,
   *buffer* and *warnings* parameters were added.

   Changed in version 3.4: The *defaultTest* parameter was changed to
   also accept an iterable of test names.


load_tests Protocol
~~~~~~~~~~~~~~~~~~~

Added in version 3.2.

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

Changed in version 3.5: 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 (last-in, first-
   out)). 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.

   Added in version 3.8.

unittest.enterModuleContext(cm)

   Enter the supplied *context manager*.  If successful, also add its
   "__exit__()" method as a cleanup function by "addModuleCleanup()"
   and return the result of the "__enter__()" method.

   Added in version 3.11.

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
   "addModuleCleanup()". 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.

   Added in version 3.8.


Signal Handling
===============

Added in version 3.2.

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):
          ...
