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"unittest" --- Unit testing framework
*************************************
New in version 2.1.
(If you are already familiar with the basic concepts of testing, you
might want to skip to the list of assert methods.)
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.
unittest2: A backport of new unittest features for Python 2.4-2.6
Many new features were added to unittest in Python 2.7, including
test discovery. unittest2 allows you to use these features with
earlier versions of Python.
Simple Smalltalk Testing: With Patterns
Kent Beck'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".
The Python Testing Tools Taxonomy
An extensive list of Python testing tools including functional
testing frameworks and mock object libraries.
Testing in Python Mailing List
A special-interest-group for discussion of testing, and testing
tools, in Python.
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 details 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
Instead of "unittest.main()", there are other ways to run the tests
with a finer level of control, less terse output, and no requirement
to be run from the command line. For example, the last two lines may
be replaced with:
suite = unittest.TestLoader().loadTestsFromTestCase(TestStringMethods)
unittest.TextTestRunner(verbosity=2).run(suite)
Running the revised script from the interpreter or another script
produces the following output:
test_isupper (__main__.TestStringMethods) ... ok
test_split (__main__.TestStringMethods) ... ok
test_upper (__main__.TestStringMethods) ... ok
----------------------------------------------------------------------
Ran 3 tests in 0.001s
OK
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.
You can run tests with more detail (higher verbosity) by passing in
the -v flag:
python -m unittest -v test_module
For a list of all the command-line options:
python -m unittest -h
Changed in version 2.7: 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.
New in version 2.7: The command-line options "-b", "-c" and "-f" were
added.
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 2.7.
Unittest supports simple test discovery. In order to be compatible
with test discovery, all of the test files must be modules or packages
importable from the top-level directory of the project (this means
that their filenames must be valid identifiers).
Test discovery is implemented in "TestLoader.discover()", but can also
be used from the command line. The basic command-line usage is:
cd project_directory
python -m unittest discover
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.
Organizing test code
====================
The basic building blocks of unit testing are *test cases* --- single
scenarios that must be set up and checked for correctness. In
"unittest", test cases are represented by instances of "unittest"'s
"TestCase" class. To make your own test cases you must write
subclasses of "TestCase", or use "FunctionTestCase".
An instance of a "TestCase"-derived class is an object that can
completely run a single test method, together with optional set-up and
tidy-up code.
The testing code of a "TestCase" instance should be entirely self
contained, such that it can be run either in isolation or in arbitrary
combination with any number of other test cases.
The simplest "TestCase" subclass will simply override the "runTest()"
method in order to perform specific testing code:
import unittest
class DefaultWidgetSizeTestCase(unittest.TestCase):
def runTest(self):
widget = Widget('The widget')
self.assertEqual(widget.size(), (50, 50), 'incorrect default size')
Note that in order to test something, we use one of the "assert*()"
methods provided by the "TestCase" base class. If the test fails, an
exception will be raised, and "unittest" will identify the test case
as a *failure*. Any other exceptions will be treated as *errors*.
This helps you identify where the problem is: *failures* are caused by
incorrect results - a 5 where you expected a 6. *Errors* are caused by
incorrect code - e.g., a "TypeError" caused by an incorrect function
call.
The way to run a test case will be described later. For now, note
that to construct an instance of such a test case, we call its
constructor without arguments:
testCase = DefaultWidgetSizeTestCase()
Now, such test cases can be numerous, and their set-up can be
repetitive. In the above case, constructing a "Widget" in each of 100
Widget test case subclasses would mean unsightly duplication.
Luckily, we can factor out such set-up code by implementing a method
called "setUp()", which the testing framework will automatically call
for us when we run the test:
import unittest
class SimpleWidgetTestCase(unittest.TestCase):
def setUp(self):
self.widget = Widget('The widget')
class DefaultWidgetSizeTestCase(SimpleWidgetTestCase):
def runTest(self):
self.assertEqual(self.widget.size(), (50,50),
'incorrect default size')
class WidgetResizeTestCase(SimpleWidgetTestCase):
def runTest(self):
self.widget.resize(100,150)
self.assertEqual(self.widget.size(), (100,150),
'wrong size after resize')
If the "setUp()" method raises an exception while the test is running,
the framework will consider the test to have suffered an error, and
the "runTest()" method will not be executed.
Similarly, we can provide a "tearDown()" method that tidies up after
the "runTest()" method has been run:
import unittest
class SimpleWidgetTestCase(unittest.TestCase):
def setUp(self):
self.widget = Widget('The widget')
def tearDown(self):
self.widget.dispose()
self.widget = None
If "setUp()" succeeded, the "tearDown()" method will be run whether
"runTest()" succeeded or not.
Such a working environment for the testing code is called a *fixture*.
Often, many small test cases will use the same fixture. In this case,
we would end up subclassing "SimpleWidgetTestCase" into many small
one-method classes such as "DefaultWidgetSizeTestCase". This is time-
consuming and discouraging, so in the same vein as JUnit, "unittest"
provides a simpler mechanism:
import unittest
class WidgetTestCase(unittest.TestCase):
def setUp(self):
self.widget = Widget('The widget')
def tearDown(self):
self.widget.dispose()
self.widget = None
def test_default_size(self):
self.assertEqual(self.widget.size(), (50,50),
'incorrect default size')
def test_resize(self):
self.widget.resize(100,150)
self.assertEqual(self.widget.size(), (100,150),
'wrong size after resize')
Here we have not provided a "runTest()" method, but have instead
provided two different test methods. Class instances will now each
run one of the "test_*()" methods, with "self.widget" created and
destroyed separately for each instance. When creating an instance we
must specify the test method it is to run. We do this by passing the
method name in the constructor:
defaultSizeTestCase = WidgetTestCase('test_default_size')
resizeTestCase = WidgetTestCase('test_resize')
Test case instances are grouped together according to the features
they test. "unittest" provides a mechanism for this: the *test suite*,
represented by "unittest"'s "TestSuite" class:
widgetTestSuite = unittest.TestSuite()
widgetTestSuite.addTest(WidgetTestCase('test_default_size'))
widgetTestSuite.addTest(WidgetTestCase('test_resize'))
For the ease of running tests, as we will see later, it is a good idea
to provide in each test module a callable object that returns a pre-
built test suite:
def suite():
suite = unittest.TestSuite()
suite.addTest(WidgetTestCase('test_default_size'))
suite.addTest(WidgetTestCase('test_resize'))
return suite
or even:
def suite():
tests = ['test_default_size', 'test_resize']
return unittest.TestSuite(map(WidgetTestCase, tests))
Since it is a common pattern to create a "TestCase" subclass with many
similarly named test functions, "unittest" provides a "TestLoader"
class that can be used to automate the process of creating a test
suite and populating it with individual tests. For example,
suite = unittest.TestLoader().loadTestsFromTestCase(WidgetTestCase)
will create a test suite that will run
"WidgetTestCase.test_default_size()" and "WidgetTestCase.test_resize".
"TestLoader" uses the "'test'" method name prefix to identify test
methods automatically.
Note that the order in which the various test cases will be run is
determined by sorting the test function names with respect to the
built-in ordering for strings.
Often it is desirable to group suites of test cases together, so as to
run tests for the whole system at once. This is easy, since
"TestSuite" instances can be added to a "TestSuite" just as "TestCase"
instances can be added to a "TestSuite":
suite1 = module1.TheTestSuite()
suite2 = module2.TheTestSuite()
alltests = unittest.TestSuite([suite1, suite2])
You can place the definitions of test cases and test suites in the
same modules as the code they are to test (such as "widget.py"), but
there are several advantages to placing the test code in a separate
module, such as "test_widget.py":
* The test module can be run standalone from the command line.
* The test code can more easily be separated from shipped code.
* There is less temptation to change test code to fit the code it
tests without a good reason.
* Test code should be modified much less frequently than the code it
tests.
* Tested code can be refactored more easily.
* Tests for modules written in C must be in separate modules anyway,
so why not be consistent?
* If the testing strategy changes, there is no need to change the
source code.
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
====================================
New in version 2.7.
Unittest supports skipping individual test methods and even whole
classes of tests. In addition, it supports marking a test as an
"expected failure," a test that is broken and will fail, but shouldn't
be counted as a failure on a "TestResult".
Skipping a test is simply a matter of using the "skip()" *decorator*
or one of its conditional variants.
Basic skipping looks like this:
class MyTestCase(unittest.TestCase):
@unittest.skip("demonstrating skipping")
def test_nothing(self):
self.fail("shouldn't happen")
@unittest.skipIf(mylib.__version__ < (1, 3),
"not supported in this library version")
def test_format(self):
# Tests that work for only a certain version of the library.
pass
@unittest.skipUnless(sys.platform.startswith("win"), "requires Windows")
def test_windows_support(self):
# windows specific testing code
pass
This is the output of running the example above in verbose mode:
test_format (__main__.MyTestCase) ... skipped 'not supported in this library version'
test_nothing (__main__.MyTestCase) ... skipped 'demonstrating skipping'
test_windows_support (__main__.MyTestCase) ... skipped 'requires Windows'
----------------------------------------------------------------------
Ran 3 tests in 0.005s
OK (skipped=3)
Classes can be skipped just like methods:
@unittest.skip("showing class skipping")
class MySkippedTestCase(unittest.TestCase):
def test_not_run(self):
pass
"TestCase.setUp()" can also skip the test. This is useful when a
resource that needs to be set up is not available.
Expected failures use the "expectedFailure()" decorator.
class ExpectedFailureTestCase(unittest.TestCase):
@unittest.expectedFailure
def test_fail(self):
self.assertEqual(1, 0, "broken")
It's easy to roll your own skipping decorators by making a decorator
that calls "skip()" on the test when it wants it to be skipped. This
decorator skips the test unless the passed object has a certain
attribute:
def skipUnlessHasattr(obj, attr):
if hasattr(obj, attr):
return lambda func: func
return unittest.skip("{!r} doesn't have {!r}".format(obj, attr))
The following decorators implement test skipping and expected
failures:
unittest.skip(reason)
Unconditionally skip the decorated test. *reason* should describe
why the test is being skipped.
unittest.skipIf(condition, reason)
Skip the decorated test if *condition* is true.
unittest.skipUnless(condition, reason)
Skip the decorated test unless *condition* is true.
unittest.expectedFailure()
Mark the test as an expected failure. If the test fails when run,
the test is not counted as a failure.
exception unittest.SkipTest(reason)
This exception is raised to skip a test.
Usually you can use "TestCase.skipTest()" or one of the skipping
decorators instead of raising this directly.
Skipped tests will not have "setUp()" or "tearDown()" run around them.
Skipped classes will not have "setUpClass()" or "tearDownClass()" run.
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 smallest testable
units in the "unittest" universe. This class is intended to be
used as a base class, with specific tests being implemented by
concrete subclasses. This class implements the interface needed by
the test runner to allow it to drive the test, and methods that the
test code can use to check for and report various kinds of failure.
Each instance of "TestCase" will run a single test method: the
method named *methodName*. If you remember, we had an earlier
example that went something like this:
def suite():
suite = unittest.TestSuite()
suite.addTest(WidgetTestCase('test_default_size'))
suite.addTest(WidgetTestCase('test_resize'))
return suite
Here, we create two instances of "WidgetTestCase", each of which
runs a single test.
*methodName* defaults to "runTest()".
"TestCase" instances provide three groups of methods: one group
used to run the test, another used by the test implementation to
check conditions and report failures, and some inquiry methods
allowing information about the test itself to be gathered.
Methods in the first group (running the test) are:
setUp()
Method called to prepare the test fixture. This is called
immediately before calling the test method; other than
"AssertionError" or "SkipTest", any exception raised by this
method will be considered an error rather than a test failure.
The default implementation does nothing.
tearDown()
Method called immediately after the test method has been called
and the result recorded. This is called even if the test method
raised an exception, so the implementation in subclasses may
need to be particularly careful about checking internal state.
Any exception, other than "AssertionError" or "SkipTest", raised
by this method will be considered an 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.
setUpClass()
A class method called before tests in an individual class 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 2.7.
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 2.7.
run(result=None)
Run the test, collecting the result into the test result object
passed as *result*. If *result* is omitted or "None", a
temporary result object is created (by calling the
"defaultTestResult()" method) and used. The result object is not
returned to "run()"'s caller.
The same effect may be had by simply calling the "TestCase"
instance.
skipTest(reason)
Calling this during a test method or "setUp()" skips the current
test. See Skipping tests and expected failures for more
information.
New in version 2.7.
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 a number of methods to check for and
report failures, such as:
+-------------------------------------------+-------------------------------+-----------------+
| Method | Checks that | New in |
+===========================================+===============================+=================+
| "assertEqual(a, b)" | "a == b" | |
+-------------------------------------------+-------------------------------+-----------------+
| "assertNotEqual(a, b)" | "a != b" | |
+-------------------------------------------+-------------------------------+-----------------+
| "assertTrue(x)" | "bool(x) is True" | |
+-------------------------------------------+-------------------------------+-----------------+
| "assertFalse(x)" | "bool(x) is False" | |
+-------------------------------------------+-------------------------------+-----------------+
| "assertIs(a, b)" | "a is b" | 2.7 |
+-------------------------------------------+-------------------------------+-----------------+
| "assertIsNot(a, b)" | "a is not b" | 2.7 |
+-------------------------------------------+-------------------------------+-----------------+
| "assertIsNone(x)" | "x is None" | 2.7 |
+-------------------------------------------+-------------------------------+-----------------+
| "assertIsNotNone(x)" | "x is not None" | 2.7 |
+-------------------------------------------+-------------------------------+-----------------+
| "assertIn(a, b)" | "a in b" | 2.7 |
+-------------------------------------------+-------------------------------+-----------------+
| "assertNotIn(a, b)" | "a not in b" | 2.7 |
+-------------------------------------------+-------------------------------+-----------------+
| "assertIsInstance(a, b)" | "isinstance(a, b)" | 2.7 |
+-------------------------------------------+-------------------------------+-----------------+
| "assertNotIsInstance(a, b)" | "not isinstance(a, b)" | 2.7 |
+-------------------------------------------+-------------------------------+-----------------+
All the assert methods (except "assertRaises()",
"assertRaisesRegexp()") accept a *msg* argument that, if specified,
is used as the error message on failure (see also "longMessage").
assertEqual(first, second, msg=None)
Test that *first* and *second* are equal. If the values do not
compare equal, the test will fail.
In addition, if *first* and *second* are the exact same type and
one of list, tuple, dict, set, frozenset or unicode or any type
that a subclass registers with "addTypeEqualityFunc()" the type-
specific equality function will be called in order to generate a
more useful default error message (see also the list of type-
specific methods).
Changed in version 2.7: Added the automatic calling of type-
specific equality function.
assertNotEqual(first, second, msg=None)
Test that *first* and *second* are not equal. If the values do
compare equal, the test will fail.
assertTrue(expr, msg=None)
assertFalse(expr, msg=None)
Test that *expr* is true (or false).
Note that this is equivalent to "bool(expr) is True" and not to
"expr is True" (use "assertIs(expr, True)" for the latter).
This method should also be avoided when more specific methods
are available (e.g. "assertEqual(a, b)" instead of "assertTrue(a
== b)"), because they provide a better error message in case of
failure.
assertIs(first, second, msg=None)
assertIsNot(first, second, msg=None)
Test that *first* and *second* evaluate (or don't evaluate) to
the same object.
New in version 2.7.
assertIsNone(expr, msg=None)
assertIsNotNone(expr, msg=None)
Test that *expr* is (or is not) None.
New in version 2.7.
assertIn(first, second, msg=None)
assertNotIn(first, second, msg=None)
Test that *first* is (or is not) in *second*.
New in version 2.7.
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 2.7.
It is also possible to check that exceptions and warnings are
raised using the following methods:
+-----------------------------------------------------------+----------------------------------------+--------------+
| Method | Checks that | New in |
+===========================================================+========================================+==============+
| "assertRaises(exc, fun, *args, **kwds)" | "fun(*args, **kwds)" raises *exc* | |
+-----------------------------------------------------------+----------------------------------------+--------------+
| "assertRaisesRegexp(exc, r, fun, *args, **kwds)" | "fun(*args, **kwds)" raises *exc* and | 2.7 |
| | the message matches regex *r* | |
+-----------------------------------------------------------+----------------------------------------+--------------+
assertRaises(exception, callable, *args, **kwds)
assertRaises(exception)
Test that an exception is raised when *callable* is called with
any positional or keyword arguments that are also passed to
"assertRaises()". The test passes if *exception* is raised, is
an error if another exception is raised, or fails if no
exception is raised. To catch any of a group of exceptions, a
tuple containing the exception classes may be passed as
*exception*.
If only the *exception* argument is given, returns a context
manager so that the code under test can be written inline rather
than as a function:
with self.assertRaises(SomeException):
do_something()
The context manager will store the caught exception object in
its "exception" attribute. This can be useful if the intention
is to perform additional checks on the exception raised:
with self.assertRaises(SomeException) as cm:
do_something()
the_exception = cm.exception
self.assertEqual(the_exception.error_code, 3)
Changed in version 2.7: Added the ability to use
"assertRaises()" as a context manager.
assertRaisesRegexp(exception, regexp, callable, *args, **kwds)
assertRaisesRegexp(exception, regexp)
Like "assertRaises()" but also tests that *regexp* matches on
the string representation of the raised exception. *regexp* may
be a regular expression object or a string containing a regular
expression suitable for use by "re.search()". Examples:
self.assertRaisesRegexp(ValueError, "invalid literal for.*XYZ'$",
int, 'XYZ')
or:
with self.assertRaisesRegexp(ValueError, 'literal'):
int('XYZ')
New in version 2.7.
There are also other methods used to perform more specific checks,
such as:
+-----------------------------------------+----------------------------------+----------------+
| Method | Checks that | New in |
+=========================================+==================================+================+
| "assertAlmostEqual(a, b)" | "round(a-b, 7) == 0" | |
+-----------------------------------------+----------------------------------+----------------+
| "assertNotAlmostEqual(a, b)" | "round(a-b, 7) != 0" | |
+-----------------------------------------+----------------------------------+----------------+
| "assertGreater(a, b)" | "a > b" | 2.7 |
+-----------------------------------------+----------------------------------+----------------+
| "assertGreaterEqual(a, b)" | "a >= b" | 2.7 |
+-----------------------------------------+----------------------------------+----------------+
| "assertLess(a, b)" | "a < b" | 2.7 |
+-----------------------------------------+----------------------------------+----------------+
| "assertLessEqual(a, b)" | "a <= b" | 2.7 |
+-----------------------------------------+----------------------------------+----------------+
| "assertRegexpMatches(s, r)" | "r.search(s)" | 2.7 |
+-----------------------------------------+----------------------------------+----------------+
| "assertNotRegexpMatches(s, r)" | "not r.search(s)" | 2.7 |
+-----------------------------------------+----------------------------------+----------------+
| "assertItemsEqual(a, b)" | sorted(a) == sorted(b) and works | 2.7 |
| | with unhashable objs | |
+-----------------------------------------+----------------------------------+----------------+
| "assertDictContainsSubset(a, b)" | all the key/value pairs in *a* | 2.7 |
| | exist in *b* | |
+-----------------------------------------+----------------------------------+----------------+
assertAlmostEqual(first, second, places=7, msg=None, delta=None)
assertNotAlmostEqual(first, second, places=7, msg=None, delta=None)
Test that *first* and *second* are approximately (or not
approximately) equal by computing the difference, rounding to
the given number of decimal *places* (default 7), and comparing
to zero. Note that these methods round the values to the given
number of *decimal places* (i.e. like the "round()" function)
and not *significant digits*.
If *delta* is supplied instead of *places* then the difference
between *first* and *second* must be less or equal to (or
greater than) *delta*.
Supplying both *delta* and *places* raises a "TypeError".
Changed in version 2.7: "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 2.7.
assertRegexpMatches(text, regexp, msg=None)
Test that a *regexp* search matches *text*. In case of failure,
the error message will include the pattern and the *text* (or
the pattern and the part of *text* that unexpectedly matched).
*regexp* may be a regular expression object or a string
containing a regular expression suitable for use by
"re.search()".
New in version 2.7.
assertNotRegexpMatches(text, regexp, msg=None)
Verifies that a *regexp* search does not match *text*. Fails
with an error message including the pattern and the part of
*text* that matches. *regexp* may be a regular expression
object or a string containing a regular expression suitable for
use by "re.search()".
New in version 2.7.
assertItemsEqual(actual, expected, msg=None)
Test that sequence *expected* contains the same elements as
*actual*, regardless of their order. When they don't, an error
message listing the differences between the sequences will be
generated.
Duplicate elements are *not* ignored when comparing *actual* and
*expected*. It verifies if each element has the same count in
both sequences. It is the equivalent of
"assertEqual(sorted(expected), sorted(actual))" but it works
with sequences of unhashable objects as well.
In Python 3, this method is named "assertCountEqual".
New in version 2.7.
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.
New in version 2.7.
Deprecated since 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 2.7.
The list of type-specific methods automatically used by
"assertEqual()" are summarized in the following table. Note that
it's usually not necessary to invoke these methods directly.
+-------------------------------------------+-------------------------------+----------------+
| Method | Used to compare | New in |
+===========================================+===============================+================+
| "assertMultiLineEqual(a, b)" | strings | 2.7 |
+-------------------------------------------+-------------------------------+----------------+
| "assertSequenceEqual(a, b)" | sequences | 2.7 |
+-------------------------------------------+-------------------------------+----------------+
| "assertListEqual(a, b)" | lists | 2.7 |
+-------------------------------------------+-------------------------------+----------------+
| "assertTupleEqual(a, b)" | tuples | 2.7 |
+-------------------------------------------+-------------------------------+----------------+
| "assertSetEqual(a, b)" | sets or frozensets | 2.7 |
+-------------------------------------------+-------------------------------+----------------+
| "assertDictEqual(a, b)" | dicts | 2.7 |
+-------------------------------------------+-------------------------------+----------------+
assertMultiLineEqual(first, second, msg=None)
Test that the multiline string *first* is equal to the string
*second*. When not equal a diff of the two strings highlighting
the differences will be included in the error message. This
method is used by default when comparing strings with
"assertEqual()".
New in version 2.7.
assertSequenceEqual(seq1, seq2, msg=None, seq_type=None)
Tests that two sequences are equal. If a *seq_type* is
supplied, both *seq1* and *seq2* must be instances of *seq_type*
or a failure will be raised. If the sequences are different an
error message is constructed that shows the difference between
the two.
This method is not called directly by "assertEqual()", but it's
used to implement "assertListEqual()" and "assertTupleEqual()".
New in version 2.7.
assertListEqual(list1, list2, msg=None)
assertTupleEqual(tuple1, tuple2, msg=None)
Tests that two lists or tuples are equal. If not, an error
message is constructed that shows only the differences between
the two. An error is also raised if either of the parameters
are of the wrong type. These methods are used by default when
comparing lists or tuples with "assertEqual()".
New in version 2.7.
assertSetEqual(set1, set2, msg=None)
Tests that two sets are equal. If not, an error message is
constructed that lists the differences between the sets. This
method is used by default when comparing sets or frozensets with
"assertEqual()".
Fails if either of *set1* or *set2* does not have a
"set.difference()" method.
New in version 2.7.
assertDictEqual(expected, actual, msg=None)
Test that two dictionaries are equal. If not, an error message
is constructed that shows the differences in the dictionaries.
This method will be used by default to compare dictionaries in
calls to "assertEqual()".
New in version 2.7.
Finally the "TestCase" provides the following methods and
attributes:
fail(msg=None)
Signals a test failure unconditionally, with *msg* or "None" for
the error message.
failureException
This class attribute gives the exception raised by the test
method. If a test framework needs to use a specialized
exception, possibly to carry additional information, it must
subclass this exception in order to "play fair" with the
framework. The initial value of this attribute is
"AssertionError".
longMessage
If set to "True" then any explicit failure message you pass in
to the assert methods will be appended to the end of the normal
failure message. The normal messages contain useful information
about the objects involved, for example the message from
assertEqual shows you the repr of the two unequal objects.
Setting this attribute to "True" allows you to have a custom
error message in addition to the normal one.
This attribute defaults to "False", meaning that a custom
message passed to an assert method will silence the normal
message.
The class setting can be overridden in individual tests by
assigning an instance attribute to "True" or "False" before
calling the assert methods.
New in version 2.7.
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 2.7.
Testing frameworks can use the following methods to collect
information on the test:
countTestCases()
Return the number of tests represented by this test object. For
"TestCase" instances, this will always be "1".
defaultTestResult()
Return an instance of the test result class that should be used
for this test case class (if no other result instance is
provided to the "run()" method).
For "TestCase" instances, this will always be an instance of
"TestResult"; subclasses of "TestCase" should override this as
necessary.
id()
Return a string identifying the specific test case. This is
usually the full name of the test method, including the module
and class name.
shortDescription()
Returns a description of the test, or "None" if no description
has been provided. The default implementation of this method
returns the first line of the test method's docstring, if
available, or "None".
addCleanup(function, *args, **kwargs)
Add a function to be called after "tearDown()" to cleanup
resources used during the test. Functions will be called in
reverse order to the order they are added (LIFO). They are
called with any arguments and keyword arguments passed into
"addCleanup()" when they are added.
If "setUp()" fails, meaning that "tearDown()" is not called,
then any cleanup functions added will still be called.
New in version 2.7.
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 2.7.
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(es) |
+================================+=================================+
| "assertEqual()" | failUnlessEqual, assertEquals |
+--------------------------------+---------------------------------+
| "assertNotEqual()" | failIfEqual |
+--------------------------------+---------------------------------+
| "assertTrue()" | failUnless, assert_ |
+--------------------------------+---------------------------------+
| "assertFalse()" | failIf |
+--------------------------------+---------------------------------+
| "assertRaises()" | failUnlessRaises |
+--------------------------------+---------------------------------+
| "assertAlmostEqual()" | failUnlessAlmostEqual |
+--------------------------------+---------------------------------+
| "assertNotAlmostEqual()" | failIfAlmostEqual |
+--------------------------------+---------------------------------+
Deprecated since version 2.7: the aliases listed in the second
column
Grouping tests
--------------
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 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.
If a module provides a "load_tests" function it will be called
to load the tests. This allows modules to customize test
loading. This is the load_tests protocol.
Changed in version 2.7: Support for "load_tests" added.
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".
discover(start_dir, pattern='test*.py', top_level_dir=None)
Find all the test modules by recursing into subdirectories from
the specified start directory, and return a TestSuite object
containing them. Only test files that match *pattern* will be
loaded. (Using shell style pattern matching.) Only module names
that are importable (i.e. are valid Python identifiers) will be
loaded.
All test modules must be importable from the top level of the
project. If the start directory is not the top level directory
then the top level directory must be specified separately.
If importing a module fails, for example due to a syntax error,
then this will be recorded as a single error and discovery will
continue.
If a test package name (directory with "__init__.py") matches
the pattern then the package will be checked for a "load_tests"
function. If this exists then it will be called with *loader*,
*tests*, *pattern*.
If load_tests exists then discovery does *not* recurse into the
package, "load_tests" is responsible for loading all tests in
the package.
The pattern is deliberately not stored as a loader attribute so
that packages can continue discovery themselves. *top_level_dir*
is stored so "load_tests" does not need to pass this argument in
to "loader.discover()".
*start_dir* can be a dotted module name as well as a directory.
New in version 2.7.
The following attributes of a "TestLoader" can be configured either
by subclassing or assignment on an instance:
testMethodPrefix
String giving the prefix of method names which will be
interpreted as test methods. The default value is "'test'".
This affects "getTestCaseNames()" and all the "loadTestsFrom*()"
methods.
sortTestMethodsUsing
Function to be used to compare method names when sorting them in
"getTestCaseNames()" and all the "loadTestsFrom*()" methods. The
default value is the built-in "cmp()" function; the attribute
can also be set to "None" to disable the sort.
suiteClass
Callable object that constructs a test suite from a list of
tests. No methods on the resulting object are needed. The
default value is the "TestSuite" class.
This affects all the "loadTestsFrom*()" methods.
class unittest.TestResult
This class is used to compile information about which tests have
succeeded and which have failed.
A "TestResult" object stores the results of a set of tests. The
"TestCase" and "TestSuite" classes ensure that results are properly
recorded; test authors do not need to worry about recording the
outcome of tests.
Testing frameworks built on top of "unittest" may want access to
the "TestResult" object generated by running a set of tests for
reporting purposes; a "TestResult" instance is returned by the
"TestRunner.run()" method for this purpose.
"TestResult" instances have the following attributes that will be
of interest when inspecting the results of running a set of tests:
errors
A list containing 2-tuples of "TestCase" instances and strings
holding formatted tracebacks. Each tuple represents a test which
raised an unexpected exception.
Changed in version 2.2: Contains formatted tracebacks instead of
"sys.exc_info()" results.
failures
A list containing 2-tuples of "TestCase" instances and strings
holding formatted tracebacks. Each tuple represents a test where
a failure was explicitly signalled using the
"TestCase.assert*()" methods.
Changed in version 2.2: Contains formatted tracebacks instead of
"sys.exc_info()" results.
skipped
A list containing 2-tuples of "TestCase" instances and strings
holding the reason for skipping the test.
New in version 2.7.
expectedFailures
A list containing 2-tuples of "TestCase" instances and strings
holding formatted tracebacks. Each tuple represents an expected
failure of the test case.
unexpectedSuccesses
A list containing "TestCase" instances that were marked as
expected failures, but succeeded.
shouldStop
Set to "True" when the execution of tests should stop by
"stop()".
testsRun
The total number of tests run so far.
buffer
If set to true, "sys.stdout" and "sys.stderr" will be buffered
in between "startTest()" and "stopTest()" being called.
Collected output will only be echoed onto the real "sys.stdout"
and "sys.stderr" if the test fails or errors. Any output is also
attached to the failure / error message.
New in version 2.7.
failfast
If set to true "stop()" will be called on the first failure or
error, halting the test run.
New in version 2.7.
wasSuccessful()
Return "True" if all tests run so far have passed, otherwise
returns "False".
stop()
This method can be called to signal that the set of tests being
run should be aborted by setting the "shouldStop" attribute to
"True". "TestRunner" objects should respect this flag and return
without running any additional tests.
For example, this feature is used by the "TextTestRunner" class
to stop the test framework when the user signals an interrupt
from the keyboard. Interactive tools which provide "TestRunner"
implementations can use this in a similar manner.
The following methods of the "TestResult" class are used to
maintain the internal data structures, and may be extended in
subclasses to support additional reporting requirements. This is
particularly useful in building tools which support interactive
reporting while tests are being run.
startTest(test)
Called when the test case *test* is about to be run.
stopTest(test)
Called after the test case *test* has been executed, regardless
of the outcome.
startTestRun()
Called once before any tests are executed.
New in version 2.7.
stopTestRun()
Called once after all 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.
class unittest.TextTestResult(stream, descriptions, verbosity)
A concrete implementation of "TestResult" used by the
"TextTestRunner".
New in version 2.7: This class was previously named
"_TextTestResult". The old name still exists as an alias but is
deprecated.
unittest.defaultTestLoader
Instance of the "TestLoader" class intended to be shared. If no
customization of the "TestLoader" is needed, this instance can be
used instead of repeatedly creating new instances.
class unittest.TextTestRunner(stream=sys.stderr, descriptions=True, verbosity=1)
A basic test runner implementation which prints results on standard
error. It has a few configurable parameters, but is essentially
very simple. Graphical applications which run test suites should
provide alternate implementations.
_makeResult()
This method returns the instance of "TestResult" used by
"run()". It is not intended to be called directly, but can be
overridden in subclasses to provide a custom "TestResult".
"_makeResult()" instantiates the class or callable passed in the
"TextTestRunner" constructor as the "resultclass" argument. It
defaults to "TextTestResult" if no "resultclass" is provided.
The result class is instantiated with the following arguments:
stream, descriptions, verbosity
unittest.main([module[, defaultTest[, argv[, testRunner[, testLoader[, exit[, verbosity[, failfast[, catchbreak[, buffer]]]]]]]]]])
A command-line program that loads a set of tests from *module* and
runs them; this is primarily for making test modules conveniently
executable. The simplest use for this function is to include the
following line at the end of a test script:
if __name__ == '__main__':
unittest.main()
You can run tests with more detailed information by passing in the
verbosity argument:
if __name__ == '__main__':
unittest.main(verbosity=2)
The *defaultTest* argument is the name of the test to run if no
test names are specified via *argv*. If not specified or "None"
and no test names are provided via *argv*, all tests found in
*module* are run.
The *argv* argument can be a list of options passed to the program,
with the first element being the program name. If not specified or
"None", the values of "sys.argv" are used.
The *testRunner* argument can either be a test runner class or an
already created instance of it. By default "main" calls
"sys.exit()" with an exit code indicating success or failure of the
tests run.
The *testLoader* argument has to be a "TestLoader" instance, and
defaults to "defaultTestLoader".
"main" supports being used from the interactive interpreter by
passing in the argument "exit=False". This displays the result on
standard output without calling "sys.exit()":
>>> from unittest import main
>>> main(module='test_module', exit=False)
The *failfast*, *catchbreak* and *buffer* parameters have the same
effect as the same-name command-line options.
Calling "main" actually returns an instance of the "TestProgram"
class. This stores the result of the tests run as the "result"
attribute.
Changed in version 2.7: The *exit*, *verbosity*, *failfast*,
*catchbreak* and *buffer* parameters were added.
load_tests Protocol
~~~~~~~~~~~~~~~~~~~
New in version 2.7.
Modules or packages can customize how tests are loaded from them
during normal test runs or test discovery by implementing a function
called "load_tests".
If a test module defines "load_tests" it will be called by
"TestLoader.loadTestsFromModule()" with the following arguments:
load_tests(loader, standard_tests, None)
It should return a "TestSuite".
*loader* is the instance of "TestLoader" doing the loading.
*standard_tests* are the tests that would be loaded by default from
the module. It is common for test modules to only want to add or
remove tests from the standard set of tests. The third argument is
used when loading packages as part of test discovery.
A typical "load_tests" function that loads tests from a specific set
of "TestCase" classes may look like:
test_cases = (TestCase1, TestCase2, TestCase3)
def load_tests(loader, tests, pattern):
suite = TestSuite()
for test_class in test_cases:
tests = loader.loadTestsFromTestCase(test_class)
suite.addTests(tests)
return suite
If discovery is started, either from the command line or by calling
"TestLoader.discover()", with a pattern that matches a package name
then the package "__init__.py" will be checked for "load_tests".
Note: The default pattern is "'test*.py'". This matches all Python
files that start with "'test'" but *won't* match any test
directories.A pattern like "'test*'" will match test packages as
well as modules.
If the package "__init__.py" defines "load_tests" then it will be
called and discovery not continued into the package. "load_tests" is
called with the following arguments:
load_tests(loader, standard_tests, pattern)
This should return a "TestSuite" representing all the tests from the
package. ("standard_tests" will only contain tests collected from
"__init__.py".)
Because the pattern is passed into "load_tests" the package is free to
continue (and potentially modify) test discovery. A 'do nothing'
"load_tests" function for a test package would look like:
def load_tests(loader, standard_tests, pattern):
# top level directory cached on loader instance
this_dir = os.path.dirname(__file__)
package_tests = loader.discover(start_dir=this_dir, pattern=pattern)
standard_tests.addTests(package_tests)
return standard_tests
Class and Module Fixtures
=========================
Class and module level fixtures are implemented in "TestSuite". When
the test suite encounters a test from a new class then
"tearDownClass()" from the previous class (if there is one) is called,
followed by "setUpClass()" from the new class.
Similarly if a test is from a different module from the previous test
then "tearDownModule" from the previous module is run, followed by
"setUpModule" from the new module.
After all the tests have run the final "tearDownClass" and
"tearDownModule" are run.
Note that shared fixtures do not play well with [potential] features
like test parallelization and they break test isolation. They should
be used with care.
The default ordering of tests created by the unittest test loaders is
to group all tests from the same modules and classes together. This
will lead to "setUpClass" / "setUpModule" (etc) being called exactly
once per class and module. If you randomize the order, so that tests
from different modules and classes are adjacent to each other, then
these shared fixture functions may be called multiple times in a
single test run.
Shared fixtures are not intended to work with suites with non-standard
ordering. A "BaseTestSuite" still exists for frameworks that don't
want to support shared fixtures.
If there are any exceptions raised during one of the shared fixture
functions the test is reported as an error. Because there is no
corresponding test instance an "_ErrorHolder" object (that has the
same interface as a "TestCase") is created to represent the error. If
you are just using the standard unittest test runner then this detail
doesn't matter, but if you are a framework author it may be relevant.
setUpClass and tearDownClass
----------------------------
These must be implemented as class methods:
import unittest
class Test(unittest.TestCase):
@classmethod
def setUpClass(cls):
cls._connection = createExpensiveConnectionObject()
@classmethod
def tearDownClass(cls):
cls._connection.destroy()
If you want the "setUpClass" and "tearDownClass" on base classes
called then you must call up to them yourself. The implementations in
"TestCase" are empty.
If an exception is raised during a "setUpClass" then the tests in the
class are not run and the "tearDownClass" is not run. Skipped classes
will not have "setUpClass" or "tearDownClass" run. If the exception is
a "SkipTest" exception then the class will be reported as having been
skipped instead of as an error.
setUpModule and tearDownModule
------------------------------
These should be implemented as functions:
def setUpModule():
createConnection()
def tearDownModule():
closeConnection()
If an exception is raised in a "setUpModule" then none of the tests in
the module will be run and the "tearDownModule" will not be run. If
the exception is a "SkipTest" exception then the module will be
reported as having been skipped instead of as an error.
Signal Handling
===============
The "-c/--catch" command-line option to unittest, along with the
"catchbreak" parameter to "unittest.main()", provide more friendly
handling of control-C during a test run. With catch break behavior
enabled control-C will allow the currently running test to complete,
and the test run will then end and report all the results so far. A
second control-c will raise a "KeyboardInterrupt" in the usual way.
The control-c handling signal handler attempts to remain compatible
with code or tests that install their own "signal.SIGINT" handler. If
the "unittest" handler is called but *isn't* the installed
"signal.SIGINT" handler, i.e. it has been replaced by the system under
test and delegated to, then it calls the default handler. This will
normally be the expected behavior by code that replaces an installed
handler and delegates to it. For individual tests that need "unittest"
control-c handling disabled the "removeHandler()" decorator can be
used.
There are a few utility functions for framework authors to enable
control-c handling functionality within test frameworks.
unittest.installHandler()
Install the control-c handler. When a "signal.SIGINT" is received
(usually in response to the user pressing control-c) all registered
results have "stop()" called.
New in version 2.7.
unittest.registerResult(result)
Register a "TestResult" object for control-c handling. Registering
a result stores a weak reference to it, so it doesn't prevent the
result from being garbage collected.
Registering a "TestResult" object has no side-effects if control-c
handling is not enabled, so test frameworks can unconditionally
register all results they create independently of whether or not
handling is enabled.
New in version 2.7.
unittest.removeResult(result)
Remove a registered result. Once a result has been removed then
"stop()" will no longer be called on that result object in response
to a control-c.
New in version 2.7.
unittest.removeHandler(function=None)
When called without arguments this function removes the control-c
handler if it has been installed. This function can also be used as
a test decorator to temporarily remove the handler whilst the test
is being executed:
@unittest.removeHandler
def test_signal_handling(self):
...
New in version 2.7.