nose: a discovery-based unittest extension.
nose provides extended test discovery and running features for
Use the nosetests script (after installation by setuptools)::
nosetests [options] [(optional) test files or directories]
In addition to passing command-line options, you may also put configuration
options in a .noserc or nose.cfg file in your home directory. These are
standard .ini-style config files. Put your nosetests configuration in a
[nosetests] section, with the -- prefix removed::
There are several other ways to use the nose test runner besides the
`nosetests` script. You may use nose in a test script::
If you don't want the test script to exit with 0 on success and 1 on failure
(like unittest.main), use nose.run() instead::
result = nose.run()
`result` will be true if the test run succeeded, or false if any test failed
or raised an uncaught exception. Lastly, you can run nose.core directly, which
will run nose.main()::
Please see the usage message for the nosetests script for information
about how to control which tests nose runs, which plugins are loaded,
and the test output.
Writing tests is easier
nose collects tests from `unittest.TestCase` subclasses, of course. But you can
also write simple test functions, and test classes that are not subclasses of
`unittest.TestCase`. nose also supplies a number of helpful functions for
writing timed tests, testing for exceptions, and other common use cases. See
`Writing tests`_ and `Testing tools`_ for more.
Running tests is easier
nose collects tests automatically, as long as you follow some simple
guidelines for organizing your library and test code. There's no need
to manually collect test cases into test suites. Running tests is
responsive, since nose begins running tests as soon as the first test
module is loaded. See `Finding and running tests`_ for more.
Setting up your test environment is easier
nose supports fixtures at the package, module, class, and test case
level, so expensive initialization can be done as infrequently as
possible. See Fixtures_ for more.
Doing what you want to do is easier
nose has plugin hooks for loading, running, watching and reporting on
tests and test runs. If you don't like the default collection scheme,
or it doesn't suit the layout of your project, or you need reports in
a format different from the unittest standard, or you need to collect
some additional information about tests (like code coverage or
profiling data), you can write a plugin to do so. See `Writing plugins`_
for more. nose comes with a number of builtin plugins, for
* Output capture
Unless called with the -s (--nocapture) switch, nose will capture stdout
during each test run, and print the captured output only for tests that
fail or have errors. The captured output is printed immediately
following the error or failure output for the test. (Note that output in
teardown methods is captured, but can't be output with failing tests,
because teardown has not yet run at the time of the failure.)
* Assert introspection
When run with the -d (--detailed-errors) switch, nose will try to output
additional information about the assert expression that failed with each
failing test. Currently, this means that names in the assert expression
will be expanded into any values found for them in the locals or globals
in the frame in which the expression executed.
In other words if you have a test like::
a = 2
assert a == 4, "assert 2 is 4"
You will get output like::
File "/path/to/file.py", line XX, in test_integers:
assert a == 4, "assert 2 is 4"
AssertionError: assert 2 is 4
>> assert 2 == 4, "assert 2 is 4"
Please note that dotted names are not expanded, and callables are not called
in the expansion.
nose may be used with the setuptools_ test command. Simply specify
nose.collector as the test suite in your setup file::
test_suite = 'nose.collector'
Then to find and run tests, you can run::
python setup.py test
When running under setuptools, you can configure nose settings via the
environment variables detailed in the nosetests script usage message,
or the setup.cfg or ~/.noserc or ~/.nose.cfg config files.
Please note that when run under the setuptools test command, some plugins will
not be available, including the builtin coverage, and profiler plugins.
nose also includes its own setuptools command, ``nosetests``, that
provides support for all plugins and command line options. See
nose.commands_ for more information about the ``nosetests`` command.
.. _setuptools: http://peak.telecommunity.com/DevCenter/setuptools
.. _nose.commands: #commands
As with py.test_, nose tests need not be subclasses of
`unittest.TestCase`. Any function or class that matches the configured
testMatch regular expression (`(?:^|[\b_\.-])[Tt]est)` by default --
that is, has test or Test at a word boundary or following a - or _)
and lives in a module that also matches that expression will be run as
a test. For the sake of compatibility with legacy unittest test cases,
nose will also load tests from `unittest.TestCase` subclasses just
like unittest does. Like py.test, functional tests will be run in the
order in which they appear in the module file. TestCase derived tests
and other test classes are run in alphabetical order.
.. _py.test: http://codespeak.net/py/current/doc/test.html
nose supports fixtures (setup and teardown methods) at the package,
module, class, and test level. As with py.test or unittest fixtures,
setup always runs before any test (or collection of tests for test
packages and modules); teardown runs if setup has completed
successfully, whether or not the test or tests pass. For more detail
on fixtures at each level, see below.
nose allows tests to be grouped into test packages. This allows
package-level setup; for instance, if you need to create a test database
or other data fixture for your tests, you may create it in package setup
and remove it in package teardown once per test run, rather than having to
create and tear it down once per test module or test case.
To create package-level setup and teardown methods, define setup and/or
teardown functions in the `__init__.py` of a test package. Setup methods may
be named `setup`, `setup_package`, `setUp`, or `setUpPackage`; teardown may
be named `teardown`, `teardown_package`, `tearDown` or `tearDownPackage`.
Execution of tests in a test package begins as soon as the first test
module is loaded from the test package.
A test module is a python module that matches the testMatch regular
expression. Test modules offer module-level setup and teardown; define the
method `setup`, `setup_module`, `setUp` or `setUpModule` for setup,
`teardown`, `teardown_module`, or `tearDownModule` for teardown. Execution
of tests in a test module begins after all tests are collected.
A test class is a class defined in a test module that is either a subclass of
`unittest.TestCase`, or matches testMatch. Test classes that don't descend
from `unittest.TestCase` are run in the same way as those that do: methods in
the class that match testMatch are discovered, and a test case constructed to
run each with a fresh instance of the test class. Like `unittest.TestCase`
subclasses, other test classes may define setUp and tearDown methods that will
be run before and after each test method. Test classes that do not descend
from `unittest.TestCase` may also include generator methods, and class-level
fixtures. Class level fixtures may be named `setup_class`, `setupClass`,
`setUpClass`, `setupAll` or `setUpAll` for set up and `teardown_class`,
`teardownClass`, `tearDownClass`, `teardownAll` or `tearDownAll` for teardown
and must be class methods.
Any function in a test module that matches testMatch will be wrapped in a
`FunctionTestCase` and run as a test. The simplest possible failing test is
And the simplest passing test::
Test functions may define setup and/or teardown attributes, which will be
run before and after the test function, respectively. A convenient way to
do this, especially when several test functions in the same module need
the same setup, is to use the provided with_setup decorator::
For python 2.3 or earlier, add the attributes by calling the decorator
function like so::
test = with_setup(setup_func, teardown_func)(test)
or by direct assignment::
test.setup = setup_func
test.teardown = teardown_func
Please note that `with_setup` is useful *only* for test functions, not
for test methods in `unittest.TestCase` subclasses or other test
classes. For those cases, define `setUp` and `tearDown` methods in the
nose supports test functions and methods that are generators. A simple
example from nose's selftest suite is probably the best explanation::
for i in range(0, 5):
yield check_even, i, i*3
def check_even(n, nn):
assert n % 2 == 0 or nn % 2 == 0
This will result in 4 tests. nose will iterate the generator, creating a
function test case wrapper for each tuple it yields. As in the example, test
generators must yield tuples, the first element of which must be a callable
and the remaining elements the arguments to be passed to the callable.
By default, the test name output for a generated test in verbose mode
will be the name of the generator function or method, followed by the
args passed to the yielded callable. If you want to show a different test
name, set the ``description`` attribute of the yielded callable.
Setup and teardown functions may be used with test generators. The setup and
teardown attributes must be attached to the generator function::
yield func, arg, arg ...
The setup and teardown functions will be executed for each test that the
For generator methods, the setUp and tearDown methods of the class (if any)
will be run before and after each generated test case.
Please note that method generators *are not* supported in `unittest.TestCase`
Finding and running tests
nose, by default, follows a few simple rules for test discovery.
* If it looks like a test, it's a test. Names of directories, modules,
classes and functions are compared against the testMatch regular
expression, and those that match are considered tests. Any class that is a
`unittest.TestCase` subclass is also collected, so long as it is inside of a
module that looks like a test.
* Directories that don't look like tests and aren't packages are not
* Packages are always inspected, but they are only collected if they look
like tests. This means that you can include your tests inside of your
packages (somepackage/tests) and nose will collect the tests without
running package code inappropriately.
* When a project appears to have library and test code organized into
separate directories, library directories are examined first.
* When nose imports a module, it adds that module's directory to sys.path;
when the module is inside of a package, like package.module, it will be
loaded as package.module and the directory of *package* will be added to
* If an object defines a __test__ attribute that does not evaluate to
True, that object will not be collected, nor will any objects it
Be aware that plugins and command line options can change any of those rules.
The nose.tools module provides a number of testing aids that you may
find useful, including decorators for restricting test execution time
and testing for exceptions, and all of the same assertX methods found
in `unittest.TestCase` (only spelled in pep08 fashion, so `assert_equal`
rather than `assertEqual`). See `nose.tools`_ for a complete list.
.. _nose.tools: http://code.google.com/p/python-nose/wiki/TestingTools
About the name
* nose is the least silly short synonym for discover in the dictionary.com
thesaurus that does not contain the word 'spy'.
* Pythons have noses
* The nose knows where to find your tests
* Nose Obviates Suite Employment
Contact the author
You can email me at jpellerin+nose at gmail dot com.
To report bugs, ask questions, or request features, please use the *issues*
tab at the Google code site: http://code.google.com/p/python-nose/issues/list.
Patches are welcome!
Similar test runners
nose was inspired mainly by py.test_, which is a great test runner, but
formerly was not all that easy to install, and is not based on unittest.
Test suites written for use with nose should work equally well with py.test,
and vice versa, except for the differences in output capture and command line
arguments for the respective tools.
.. _py.test: http://codespeak.net/py/current/doc/test.html
License and copyright
nose is copyright Jason Pellerin 2005-2007
This program is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2 of the License, or (at your
option) any later version.
This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
License for more details.
You should have received a copy of the GNU Lesser General Public License
along with this program; if not, write to the Free Software Foundation,
Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA