An extension for colcon-core <https://github.com/colcon/colcon-core>_ to provide aggregate coverage results using LCOV <http://ltp.sourceforge.net/coverage/lcov.php>_.

LCOV is a graphical front-end for GCC's coverage testing tool gcov <https://gcc.gnu.org/onlinedocs/gcc/Gcov.html>_, producing the following coverage metrics:

• Statement coverage
• Function coverage
• Branch coverage

For more information, see this paper <http://ltp.sourceforge.net/documentation/technical_papers/gcov-ols2003.pdf>_ and this Wikipedia page <https://en.wikipedia.org/wiki/Code_coverage>_.

Usage

#. Build your packages with coverage flags, using colcon:

.. code-block:: shell

 $ colcon build \
       --symlink-install \
       --cmake-args \
           -DCMAKE_CXX_FLAGS='-fprofile-arcs -ftest-coverage' \
           -DCMAKE_C_FLAGS='-fprofile-arcs -ftest-coverage'

• See also colcon-mixin <https://github.com/colcon/colcon-mixin>_ and colcon-mixin-repository <https://github.com/colcon/colcon-mixin-repository/blob/master/coverage.mixin>_ for a short-hand command (--mixin coverage-gcc)

#. Create a baseline for zero coverage:

.. code-block:: shell

 $ colcon lcov-result --initial

• This step is optional, but will help reveal any files that are untouched by tests

#. Run tests:

.. code-block:: shell

 $ colcon test

#. Gather the lcov results:

.. code-block:: shell

 $ colcon lcov-result
 Reading tracefile /home/user/workspace/my_cool_ws/lcov/total_coverage.info
 Summary coverage rate:
   lines......: 78.6% (44 of 56 lines)
   functions..: 94.4% (34 of 36 functions)
   branches...: 37.0% (34 of 92 branches)

#. Browse the coverage report by opening lcov/index.html in a browser

#. Zero the coverage counters and re-run tests:

.. code-block:: shell

 $ colcon lcov-result --zero-counters
 $ colcon lcov-result --initial
 $ colcon test
 $ colcon lcov-result
 Reading tracefile /home/user/workspace/my_cool_ws/lcov/total_coverage.info
 Summary coverage rate:
   lines......: 78.6% (44 of 56 lines)
   functions..: 94.4% (34 of 36 functions)
   branches...: 37.0% (34 of 92 branches)

Tips and Tricks

• When running locally, use the --packages-select option to generate coverage information for relevant packages

  • This will also suppress warnings for packages that were either not built with coverage flags or for which tests did not run

• The --verbose flag can be used to print the coverage summary of each individual package as the results are analyzed

Contributing

For non-trivial contributions, it is recommended to first create an issue to discuss your ideas.

The following is the recommended workflow for contributing:

#. Install colcon and extensions in a virtual environment:

.. code-block:: shell

 $ cd <workspace>
 $ python3 -m venv colcon-env
 $ source colcon-env/bin/activate
 $ pip3 install colcon-common-extensions

#. Install colcon-lcov-result in editable mode:

.. code-block:: shell

 $ cd <workspace>
 $ python3 -m venv colcon-env
 $ source colcon-env/bin/activate
 $ cd path/to/colcon-lcov-result
 $ pip3 install -e .

#. As long as you are in the virtual environment, make changes to colcon-lcov-result run colcon lcov-result, and see the effect of the changes

#. Commit changes and submit a PR:

• See The seven rules of a great Git commit message_

.. _The seven rules of a great Git commit message: https://chris.beams.io/posts/git-commit/#seven-rules

Troubleshooting

• The following warning when running colcon lcov-result --initial implies that the package was not built with the correct flags:

  .. code-block:: shell

  --- stderr: my_pkg
  geninfo: WARNING: no .gcno files found in /home/user/workspace/build/my_pkg - skipping!

  • The package will not show up in the final results. Use --packages-skip to suppress the warning

• The following warning when running colcon lcov-result implies that no tests ran for that package

  .. code-block:: shell

  [0.576s] ERROR:colcon.colcon_lcov_result.task.lcov:lcov: ERROR: no valid records found in tracefile /home/user/workspace/build/my_pkg/coverage.info --- stderr: my_pkg geninfo: WARNING: no .gcda files found in /home/user/workspace/build/my_pkg - skipping!

  • The package will show up in the final results with 0% coverage. Use --packages-skip to suppress these packages from the total

Known Issues

#. The final step of aggregating all the result files can be slow depending on the number of packages that were analyzed

Developing

See DEVELOPING.md <DEVELOPING.md>_.