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nose plugin for coverage reporting, including subprocesses and multiprocessing

Project description

This plugin produces coverage reports. It also supports coverage of subprocesses.

All features offered by the coverage package should be available, either through nose-cov or through coverage’s config file.


Install with pip:

pip install nose-cov


Ensure you use pip instead of easy_install as the latter does not correctly install the init_cov_core.pth file needed for subprocess measurement.


Uninstall with pip:

pip uninstall nose-cov
pip uninstall cov-core


Ensure that you manually delete the init_cov_core.pth file in your site-packages directory.

This file starts coverage collection of subprocesses if appropriate during site initialisation at python startup.


The following will report on the combined coverage of the main process and all of it’s subprocesses:

nosetests --with-cov --cov myproj tests/

Shows a terminal report:

---------- coverage: platform linux2, python 2.6.5-final-0 -----------
Name                 Stmts   Miss  Cover
myproj/__init__          2      0   100%
myproj/myproj          257     13    95%
myproj/feature4286      94      9    90%
TOTAL                  353     22    94%


It is possible to generate any combination of the reports for a single test run.

The available reports are terminal (with or without missing line numbers shown), HTML, XML and annotated source code.

The terminal report without line numbers (default):

nosetests --with-cov --cov-report term --cov myproj tests/

---------- coverage: platform linux2, python 2.6.5-final-0 -----------
Name                 Stmts   Miss  Cover
myproj/__init__          2      0   100%
myproj/myproj          257     13    95%
myproj/feature4286      94      9    90%
TOTAL                  353     22    94%

The terminal report with line numbers:

nosetests --with-cov --cov-report term-missing --cov myproj tests/

---------- coverage: platform linux2, python 2.6.5-final-0 -----------
Name                 Stmts   Miss  Cover   Missing
myproj/__init__          2      0   100%
myproj/myproj          257     13    95%   24-26, 99, 149, 233-236, 297-298, 369-370
myproj/feature4286      94      9    90%   37, 40, 183-188, 197
TOTAL                  353     22    94%

The remaining three reports output to files without showing anything on the terminal (useful for when the output is going to a continuous integration server):

nosetests --with-cov
          --cov-report html
          --cov-report xml
          --cov-report annotate
          --cov myproj tests/

Coverage Data File

The data file is erased at the beginning of testing to ensure clean data for each test run.

The data file is left at the end of testing so that it is possible to use normal coverage tools to examine it.

Coverage Config File

This plugin provides a clean minimal set of command line options that are added to nosetests. For further control of coverage use a coverage config file.

For example if tests are contained within the directory tree being measured the tests may be excluded if desired by using a .coveragerc file with the omit option set:

nosetests --cov-config .coveragerc
          --cov myproj

Where the .coveragerc file contains file globs:

omit = tests/*

For full details refer to the coverage config file documentation.

Note that this plugin controls some options and setting the option in the config file will have no effect. These include specifying source to be measured (source option) and all data file handling (data_file and parallel options).


For subprocess measurement environment variables must make it from the main process to the subprocess. The python used by the subprocess must have nose-cov installed. The subprocess must do normal site initialisation so that the environment variables can be detected and coverage started.

Nose Multiprocess Plugin

The nose cov plugin partially works with the nose multiprocess plugin.

The nose multiprocess plugin does not join with its child processes so nose cov plugin has coverage measured but can’t merge coverage results and report them.

Work around by using cov plugin and multiprocess plugin together to run tests, note coverage report from this command will be incorrect:

nosetests --with-cov --processes=4 tests/

After there will be coverage data files for the main nose process and each subprocess:


Tell coverage to merge coverage results into one coverage data file:

coverage combine

Tell coverage to report:

coverage report


Whilst this plugin has been built fresh from the ground up it has been influenced by the work done on pytest-coverage (Ross Lawley, James Mills, Holger Krekel) and nose-cover (Jason Pellerin) which are other coverage plugins.

Ned Batchelder for coverage and its ability to combine the coverage results of parallel runs.

Holger Krekel for pytest with its distributed testing support.

Jason Pellerin for nose.

Michael Foord for unittest2.

No doubt others have contributed to these tools as well.

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