
``unittest`` --- Unit testing framework
***************************************

Changed in version 3.1: Added test *skipping and expected failures*.

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

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

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

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

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

test suite
   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.

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

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

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

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``.

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

   python-mock and minimock
      Tools for creating mock test objects (objects simulating
      external resources).


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 functions from the ``random``
module:

   import random
   import unittest

   class TestSequenceFunctions(unittest.TestCase):

       def setUp(self):
           self.seq = list(range(10))

       def test_shuffle(self):
           # make sure the shuffled sequence does not lose any elements
           random.shuffle(self.seq)
           self.seq.sort()
           self.assertEqual(self.seq, list(range(10)))

       def test_choice(self):
           element = random.choice(self.seq)
           self.assertIn(element, self.seq)

       def test_sample(self):
           self.assertRaises(ValueError, random.sample, self.seq, 20)
           for element in random.sample(self.seq, 5):
               self.assertIn(element, self.seq)

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

A testcase 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; ``assert_()`` to verify a condition; or
``assertRaises()`` to verify that an expected 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.

When a ``setUp()`` method is defined, the test runner will run that
method prior to each test.  Likewise, if a ``tearDown()`` method is
defined, the test runner will invoke that method after each test.  In
the example, ``setUp()`` was used to create a fresh sequence for each
test.

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

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

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

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

   test_choice (__main__.TestSequenceFunctions) ... ok
   test_sample (__main__.TestSequenceFunctions) ... ok
   test_shuffle (__main__.TestSequenceFunctions) ... ok

   ----------------------------------------------------------------------
   Ran 3 tests in 0.110s

   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.


Organizing test code
====================

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

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

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

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

   import unittest

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

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

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

   testCase = DefaultWidgetSizeTestCase()

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

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

   import unittest

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

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

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

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

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

   import unittest

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

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

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

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

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

   import unittest

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

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

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

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

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

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

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

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

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

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

or even:

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

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

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

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

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

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

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

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

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

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

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

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

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

* Tested code can be refactored more easily.

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

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


Re-using old test code
======================

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

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

Given the following test function:

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

one can create an equivalent test case instance as follows:

   testcase = unittest.FunctionTestCase(testSomething)

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

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

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

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

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

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

Basic skipping looks like this:

   class MyTestCase(unittest.TestCase):

       @unittest.skip("demonstrating skipping")
       def test_nothing(self):
           self.fail("shouldn't happen")

       @unittest.skipIf(mylib.__version__ < (1, 3), "not supported in this library version")
       def test_format(self):
           # Tests that work for only a certain version of the library.
           pass

       @unittest.skipUnless(sys.platform.startswith("win"), "requires Windows")
       def test_windows_support(self):
           # windows specific testing code
           pass

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

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

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

   OK (skipped=3)

Classes can be skipped just like methods:

   @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("{0!r} doesn't have {1!r}".format(obj, attr))

The following decorators implement test skipping and expected
failures:

unittest.skip(reason)

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

unittest.skipIf(condition, reason)

   Skip the decorated test if *condition* is true.

unittest.skipUnless(condition, reason)

   Skip the decoratored test unless *condition* is true.

unittest.expectedFailure()

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


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

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


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

class class unittest.TestCase(methodName='runTest')

   Instances of the ``TestCase`` class represent the smallest testable
   units in the ``unittest`` universe.  This class is intended to be
   used as a base class, with specific tests being implemented by
   concrete subclasses.  This class implements the interface needed by
   the test runner to allow it to drive the test, and methods that the
   test code can use to check for and report various kinds of failure.

   Each instance of ``TestCase`` will run a single test method: the
   method named *methodName*.  If you remember, we had an earlier
   example that went something like this:

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

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

   *methodName* defaults to ``runTest()``.

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

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

   setUp()

      Method called to prepare the test fixture.  This is called
      immediately before calling the test method; 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 raised by this method will be considered an error
      rather than a test failure.  This method will only be called if
      the ``setUp()`` succeeds, regardless of the outcome of the test
      method. The default implementation does nothing.

   run(result=None)

      Run the test, collecting the result into the test result object
      passed as *result*.  If *result* is omitted or ``None``, a
      temporary result object is created (by calling the
      ``defaultTestResult()`` method) and used. The result object is
      not returned to ``run()``'s caller.

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

   skipTest(reason)

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

   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 test code can use any of the following methods to check for and
   report failures.

   assertTrue(expr, msg=None)
   assert_(expr, msg=None)
   failUnless(expr, msg=None)

      Signal a test failure if *expr* is false; the explanation for
      the failure will be *msg* if given, otherwise it will be
      ``None``.

      Deprecated since version 3.1: ``failUnless()``.

   assertEqual(first, second, msg=None)
   failUnlessEqual(first, second, msg=None)

      Test that *first* and *second* are equal.  If the values do not
      compare equal, the test will fail with the explanation given by
      *msg*, or ``None``.  Note that using ``assertEqual()`` improves
      upon doing the comparison as the first parameter to
      ``assertTrue()``: the default value for *msg* include
      representations of both *first* and *second*.

      In addition, if *first* and *second* are the exact same type and
      one of list, tuple, dict, set, or frozenset or any type that a
      subclass registers ``addTypeEqualityFunc()`` the type specific
      equality function will be called in order to generate a more
      useful default error message.

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

      Deprecated since version 3.1: ``failUnlessEqual()``.

   assertNotEqual(first, second, msg=None)
   failIfEqual(first, second, msg=None)

      Test that *first* and *second* are not equal.  If the values do
      compare equal, the test will fail with the explanation given by
      *msg*, or ``None``.  Note that using ``assertNotEqual()``
      improves upon doing the comparison as the first parameter to
      ``assertTrue()`` is that the default value for *msg* can be
      computed to include representations of both *first* and
      *second*.

      Deprecated since version 3.1: ``failIfEqual()``.

   assertAlmostEqual(first, second, *, places=7, msg=None)
   failUnlessAlmostEqual(first, second, *, places=7, msg=None)

      Test that *first* and *second* are approximately equal by
      computing the difference, rounding to the given number of
      decimal *places* (default 7), and comparing to zero.

      Note that comparing a given number of decimal places is not the
      same as comparing a given number of significant digits. If the
      values do not compare equal, the test will fail with the
      explanation given by *msg*, or ``None``.

      Deprecated since version 3.1: ``failUnlessAlmostEqual()``.

   assertNotAlmostEqual(first, second, *, places=7, msg=None)
   failIfAlmostEqual(first, second, *, places=7, msg=None)

      Test that *first* and *second* are not approximately equal by
      computing the difference, rounding to the given number of
      decimal *places* (default 7), and comparing to zero.

      Note that comparing a given number of decimal places is not the
      same as comparing a given number of significant digits. If the
      values do not compare equal, the test will fail with the
      explanation given by *msg*, or ``None``.

      Deprecated since version 3.1: ``failIfAlmostEqual()``.

   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 with
      an explanation or with the explanation given by *msg*:

         >>> self.assertGreaterEqual(3, 4)
         AssertionError: "3" unexpectedly not greater than or equal to "4"

      New in version 3.1.

   assertMultiLineEqual(self, 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.

      If specified *msg* will be used as the error message on failure.

      New in version 3.1.

   assertRegexpMatches(text, regexp, msg=None):

      Verifies that a *regexp* search matches *text*.  Fails with an
      error message including the pattern and the *text*.  *regexp*
      may be a regular expression object or a string containing a
      regular expression suitable for use by ``re.search()``.

      New in version 3.1.

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

      Tests that *first* is or is not in *second* with an explanatory
      error message as appropriate.

      If specified *msg* will be used as the error message on failure.

      New in version 3.1.

   assertSameElements(actual, expected, msg=None)

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

      Duplicate elements are ignored when comparing *actual* and
      *expected*. It is the equivalent of ``assertEqual(set(expected),
      set(actual))`` but it works with sequences of unhashable objects
      as well.

      If specified *msg* will be used as the error message on failure.

      New in version 3.1.

   assertSetEqual(set1, set2, msg=None)

      Tests that two sets are equal.  If not, an error message is
      constructed that lists the differences between the sets.

      Fails if either of *set1* or *set2* does not have a
      ``set.difference()`` method.

      If specified *msg* will be used as the error message on failure.

      New in version 3.1.

   assertDictEqual(expected, actual, msg=None)

      Test that two dictionaries are equal.  If not, an error message
      is constructed that shows the differences in the dictionaries.

      If specified *msg* will be used as the error message on failure.

      New in version 3.1.

   assertDictContainsSubset(expected, actual, msg=None)

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

      If specified *msg* will be used as the error message on failure.

      New in version 3.1.

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

      Tests that two lists or tuples are equal.  If not an error
      message is constructed that shows only the differences between
      the two.  An error is also raised if either of the parameters
      are of the wrong type.

      If specified *msg* will be used as the error message on failure.

      New in version 3.1.

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

      Tests that two sequences are equal.  If a *seq_type* is
      supplied, both *seq1* and *seq2* must be instances of *seq_type*
      or a failure will be raised.  If the sequences are different an
      error message is constructed that shows the difference between
      the two.

      If specified *msg* will be used as the error message on failure.

      This method is used to implement ``assertListEqual()`` and
      ``assertTupleEqual()``.

      New in version 3.1.

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

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

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

         with self.assertRaises(SomeException):
             do_something()

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

      Deprecated since version 3.1: ``failUnlessRaises()``.

   assertRaisesRegexp(exception, regexp[, callable, ...])

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

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

      or:

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

      New in version 3.1.

   assertIsNone(expr, msg=None)

      This signals a test failure if *expr* is not None.

      New in version 3.1.

   assertIsNotNone(expr, msg=None)

      The inverse of the ``assertIsNone()`` method. This signals a
      test failure if *expr* is None.

      New in version 3.1.

   assertIs(expr1, expr2, msg=None)

      This signals a test failure if *expr1* and *expr2* don't
      evaluate to the same object.

      New in version 3.1.

   assertIsNot(expr1, expr2, msg=None)

      The inverse of the ``assertIs()`` method. This signals a test
      failure if *expr1* and *expr2* evaluate to the same object.

      New in version 3.1.

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

      The inverse of the ``assertTrue()`` method is the
      ``assertFalse()`` method. This signals a test failure if *expr*
      is true, with *msg* or ``None`` for the error message.

      Deprecated since version 3.1: ``failIf()``.

   fail(msg=None)

      Signals a test failure unconditionally, with *msg* or ``None``
      for the error message.

   failureException

      This class attribute gives the exception raised by the test
      method.  If a test framework needs to use a specialized
      exception, possibly to carry additional information, it must
      subclass this exception in order to "play fair" with the
      framework.  The initial value of this attribute is
      ``AssertionError``.

   longMessage

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

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

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

      New in version 3.1.

   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, along with the method name.

      Changed in version 3.1: In earlier versions this only returned
      the first line of the test method's docstring, if available or
      the ``None``.  That led to undesirable behavior of not printing
      the test name when someone was thoughtful enough to write a
      docstring.

   addTypeEqualityFunc(typeobj, function)

      Registers a type specific ``assertEqual()`` equality checking
      function to be called by ``assertEqual()`` when both objects it
      has been asked to compare are exactly *typeobj* (not
      subclasses). *function* must take two positional arguments and a
      third msg=None keyword argument just as ``assertEqual()`` does.
      It must raise ``self.failureException`` when inequality between
      the first two parameters is detected.

      One good use of custom equality checking functions for a type is
      to raise ``self.failureException`` with an error message useful
      for debugging the problem by explaining the inequalities in
      detail.

      New in version 3.1.

   addCleanup(function, *args, **kwargs)

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

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

      New in version 2.7.

   doCleanups()

      This method is called uncoditionally 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.

      New in version 2.7.

class 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 class unittest.TestSuite(tests=())

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

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

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

   addTest(test)

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

   addTests(tests)

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

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

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

   run(result)

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

   debug()

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

   countTestCases()

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

   __iter__()

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

      Changed in version 2.7: In earlier versions the ``TestSuite``
      accessed tests directly rather than through iteration, so
      overriding ``__iter__()`` wasn't sufficient for providing tests.

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


Loading and running tests
-------------------------

class class unittest.TestLoader

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

   ``TestLoader`` objects have the following methods:

   loadTestsFromTestCase(testCaseClass)

      Return a suite of all tests cases contained in the
      ``TestCase``-derived ``testCaseClass``.

   loadTestsFromModule(module)

      Return a suite of all tests 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.

   loadTestsFromName(name, module=None)

      Return a suite of all tests cases given a string specifier.

      The specifier *name* is a "dotted name" that may resolve either
      to a module, a test case class, a test method within a test case
      class, a ``TestSuite`` instance, or a callable object which
      returns a ``TestCase`` or ``TestSuite`` instance.  These checks
      are applied in the order listed here; that is, a method on a
      possible test case class will be picked up as "a test method
      within a test case class", rather than "a callable object".

      For example, if you have a module ``SampleTests`` containing a
      ``TestCase``-derived class ``SampleTestCase`` with three test
      methods (``test_one()``, ``test_two()``, and ``test_three()``),
      the specifier ``'SampleTests.SampleTestCase'`` would cause this
      method to return a suite which will run all three test methods.
      Using the specifier ``'SampleTests.SampleTestCase.test_two'``
      would cause it to return a test suite which will run only the
      ``test_two()`` test method.  The specifier can refer to modules
      and packages which have not been imported; they will be imported
      as a side-effect.

      The method optionally resolves *name* relative to the given
      *module*.

   loadTestsFromNames(names, module=None)

      Similar to ``loadTestsFromName()``, but takes a sequence of
      names rather than a single name.  The return value is a test
      suite which supports all the tests defined for each name.

   getTestCaseNames(testCaseClass)

      Return a sorted sequence of method names found within
      *testCaseClass*; this should be a subclass of ``TestCase``.

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

   testMethodPrefix

      String giving the prefix of method names which will be
      interpreted as test methods.  The default value is ``'test'``.

      This affects ``getTestCaseNames()`` and all the
      ``loadTestsFrom*()`` methods.

   sortTestMethodsUsing

      Function to be used to compare method names when sorting them in
      ``getTestCaseNames()`` and all the ``loadTestsFrom*()`` methods.

   suiteClass

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

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

class class unittest.TestResult

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

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

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

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

   errors

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

   failures

      A list containing 2-tuples of ``TestCase`` instances and strings
      holding formatted tracebacks. Each tuple represents a test where
      a failure was explicitly signalled using the
      ``TestCase.fail*()`` or ``TestCase.assert*()`` methods.

   skipped

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

      New in version 3.1.

   expectedFailures

      A list contaning 2-tuples of ``TestCase`` instances and strings
      holding formatted tracebacks.  Each tuple represents a expected
      failures of the test case.

   unexpectedSuccesses

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

   shouldStop

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

   testsRun

      The total number of tests run so far.

   wasSuccessful()

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

   stop()

      This method can be called to signal that the set of tests being
      run should be aborted by setting the ``shouldStop`` attribute to
      ``True``. ``TestRunner`` objects should respect this flag and
      return without running any additional tests.

      For example, this feature is used by the ``TextTestRunner``
      class to stop the test framework when the user signals an
      interrupt from the keyboard.  Interactive tools which provide
      ``TestRunner`` implementations can use this in a similar manner.

   The following methods of the ``TestResult`` class are used to
   maintain the internal data structures, and may be extended in
   subclasses to support additional reporting requirements.  This is
   particularly useful in building tools which support interactive
   reporting while tests are being run.

   startTest(test)

      Called when the test case *test* is about to be run.

      The default implementation simply increments the instance's
      ``testsRun`` counter.

   stopTest(test)

      Called after the test case *test* has been executed, regardless
      of the outcome.

      The default implementation does nothing.

   startTestRun(test)

      Called once before any tests are executed.

      New in version 2.7.

   stopTestRun(test)

      Called once before any tests are executed.

      New in version 2.7.

   addError(test, err)

      Called when the test case *test* raises an unexpected exception
      *err* is a tuple of the form returned by ``sys.exc_info()``:
      ``(type, value, traceback)``.

      The default implementation appends a tuple ``(test,
      formatted_err)`` to the instance's ``errors`` attribute, where
      *formatted_err* is a formatted traceback derived from *err*.

   addFailure(test, err)

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

      The default implementation appends a tuple ``(test,
      formatted_err)`` to the instance's ``failures`` attribute, where
      *formatted_err* is a formatted traceback derived from *err*.

   addSuccess(test)

      Called when the test case *test* succeeds.

      The default implementation does nothing.

   addSkip(test, reason)

      Called when the test case *test* is skipped.  *reason* is the
      reason the test gave for skipping.

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

   addExpectedFailure(test, err)

      Called when the test case *test* fails, but was marked with the
      ``expectedFailure()`` decorator.

      The default implementation appends a tuple ``(test,
      formatted_err)`` to the instance's ``expectedFailures``
      attribute, where *formatted_err* is a formatted traceback
      derived from *err*.

   addUnexpectedSuccess(test)

      Called when the test case *test* was marked with the
      ``expectedFailure()`` decorator, but succeeded.

      The default implementation appends the test to the instance's
      ``unexpectedSuccesses`` attribute.

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 class unittest.TextTestRunner(stream=sys.stderr, descriptions=True, verbosity=1)

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

   _makeResult()

      This method returns the instance of ``TestResult`` used by
      ``run()``. It is not intended to be called directly, but can be
      overridden in subclasses to provide a custom ``TestResult``.

unittest.main(module='__main__', defaultTest=None, argv=None, testRunner=TextTestRunner, testLoader=unittest.defaultTestLoader, exit=True)

   A command-line program that runs a set of tests; 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()

   The *testRunner* argument can either be a test runner class or an
   already created instance of it. By default ``main`` calls
   ``sys.exit()`` with an exit code indicating success or failure of
   the tests run.

   ``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)

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

   Changed in version 2.7: The ``exit`` parameter was added.
