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.

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

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 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.

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

New in version 3.5: The command-line option --locals.

New in version 3.7: The command-line option -k.

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

New 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 (including namespace 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.

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 __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

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

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

OK (skipped=4)

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. If the test fails 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

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

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

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

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

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

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.

New 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.

New 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.

New 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.

New 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 evaluate (or don’t evaluate) to the same object.

New in version 3.1.

assertIsNone ( expr, msg=None )
assertIsNotNone ( expr, msg=None ): Test that expr is (or is not) None.

New in version 3.1.

assertIn ( member, container, msg=None )
assertNotIn ( member, container, msg=None ): Test that member is (or is not) in container.

New 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).

New 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 the message matches regex r	3.1
`assertWarns(warn, fun, args, *kwds)`	`fun(args, kwds)` raises warn*	3.2
`assertWarnsRegex(warn, r, fun, args, *kwds)`	`fun(args, kwds)` raises warn* and the message matches regex r	3.2
`assertLogs(logger, level)`	The `with` block logs on logger with minimum level	3.4

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

assertRaises ( exception, *, msg=None )

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

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

with self.assertRaises(SomeException):
    do_something()

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

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

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

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

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')

New 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.

New 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')

New 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.

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'])

New in version 3.4.

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

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

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

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

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

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

Supplying both delta and places raises a TypeError.

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"

New 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().

New in version 3.1: Added under the name assertRegexpMatches.

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

New in version 3.2: assertNotRegex().

New in version 3.5: The name assertNotRegexpMatches is a deprecated alias for 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.

New 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.

New 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().

New 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().

New 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().

New 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 set.difference() method.

New 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().

New 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.

New 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.

New 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). 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 3.1.

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.

New 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). 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.

New in version 3.8.

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 addCleanupClass(). If you need cleanup functions to be called prior to tearDownClass() then you can call doCleanupsClass() yourself.

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

New in version 3.8.

class unittest. IsolatedAsyncioTestCase ( methodName='runTest' )

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

New in version 3.8.

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

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

addAsyncCleanup ( function, /, *args, **kwargs ): This method accepts a coroutine that can be used as a cleanup function.

run ( result=None ): Sets up a new event loop to run the test, collecting the result into the TestResult object passed as result. If result is omitted or None, a temporary result object is created (by calling the defaultTestResult() method) and used. The result object is returned to run()’s caller. At the end of the test all the tasks in the event loop are cancelled.

An example illustrating the order:

from unittest import IsolatedAsyncioTestCase

events = []

class Test(IsolatedAsyncioTestCase):

    def setUp(self):
        events.append("setUp")

    async def asyncSetUp(self):
        self._async_connection = await AsyncConnection()
        events.append("asyncSetUp")

    async def test_response(self):
        events.append("test_response")
        response = await self._async_connection.get("https://example.com")
        self.assertEqual(response.status_code, 200)
        self.addAsyncCleanup(self.on_cleanup)

    def tearDown(self):
        events.append("tearDown")

    async def asyncTearDown(self):
        await self._async_connection.close()
        events.append("asyncTearDown")

    async def on_cleanup(self):
        events.append("cleanup")

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

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

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

Deprecated aliases

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

Method Name

Deprecated alias

Deprecated alias

assertEqual()

failUnlessEqual

assertEquals

assertNotEqual()

failIfEqual

assertNotEquals

assertTrue()

failUnless

assert_

assertFalse()

failIf

assertRaises()

failUnlessRaises

assertAlmostEqual()

failUnlessAlmostEqual

assertAlmostEquals

assertNotAlmostEqual()

failIfAlmostEqual

assertNotAlmostEquals

assertRegex()

assertRegexpMatches

assertNotRegex()

assertNotRegexpMatches

assertRaisesRegex()

assertRaisesRegexp

Deprecated since version 3.1: The fail* aliases listed in the second column have been deprecated.

Deprecated since version 3.2: The assert* aliases listed in the third column have been deprecated.

Deprecated since version 3.2: assertRegexpMatches and assertRaisesRegexp have been renamed to assertRegex() and assertRaisesRegex().

Deprecated since version 3.5: The assertNotRegexpMatches name is deprecated in favor of assertNotRegex().

Docs

Docs4dev

Title here

unittest — Unit testing framework

Basic example

Command-Line Interface

Command-line options

Test Discovery

Organizing test code

Re-using old test code

Skipping tests and expected failures

Distinguishing test iterations using subtests

Classes and functions

Test cases

Deprecated aliases

Method Name	Deprecated alias	Deprecated alias
`assertEqual()`	failUnlessEqual	assertEquals
`assertNotEqual()`	failIfEqual	assertNotEquals
`assertTrue()`	failUnless	assert_
`assertFalse()`	failIf
`assertRaises()`	failUnlessRaises
`assertAlmostEqual()`	failUnlessAlmostEqual	assertAlmostEquals
`assertNotAlmostEqual()`	failIfAlmostEqual	assertNotAlmostEquals
`assertRegex()`		assertRegexpMatches
`assertNotRegex()`		assertNotRegexpMatches
`assertRaisesRegex()`		assertRaisesRegexp