This document contains:

How to report bugs

When reporting a bug, first search our issues to avoid duplicates. In your bug report, please describe what you expected gcovr to do, and what it actually did. Also try to include the following details:

  • how you invoked gcovr, i.e. the exact flags and from which directory
  • your project layout
  • your gcovr version
  • your compiler version
  • your operating system
  • and any other relevant details.

Ideally, you can provide a short script and the smallest possible source file to reproduce the problem.

How to help

If you would like to help out, please take a look at our open issues and pull requests. The issues labeled help wanted and needs review would have the greatest impact.

There are many ways how you can help:

  • assist other users with their problems
  • share your perspective as a gcovr user in discussions
  • test proposed changes in your real-world projects
  • improve our documentation
  • submit pull requests with bug fixes and enhancements

How to submit a Pull Request

Thank you for helping with gcovr development! Please follow this checklist for your pull request:

  • Is this a good approach? Fixing open issues is always welcome! If you want to implement an enhancement, please discuss it first as a GitHub issue.

  • Does it work? Please run the tests locally:

    python -m pytest

    In any case, the tests will run automatically when you open the pull request. But please prevent unnecessary build failures and run the tests yourself first. If you cannot run the tests locally, you can activate Travis CI or Appveyor for your fork.

    If you add new features, please try to add a test case.

  • Does it conform to the style guide? The source code should conform to the PEP 8 standard. Please check your code:

    python -m flake8 doc gcovr --ignore E501
  • Add yourself as an author. If this is your first contribution to gcovr, please add yourself to the AUTHORS.txt file.

  • One change at a time. Please keep your commits and your whole pull request fairly small, so that the changes are easy to review. Each commit should only contain one kind of change, e.g. refactoring or new functionality.

  • Why is this change necessary? When you open the PR, please explain why we need this change and what your PR does. If this PR fixes an open issue, reference that issue in the pull request description.

Once you submit the PR, it will be automatically tested on Windows and Linux, and code coverage will be collected. Your code will be reviewed. This can take a week. Please fix any issues that are discovered during this process. Feel free to force-push your updates to the pull request branch.

If you need assistance for your pull request, you can

  • chat in our Gitter room
  • discuss your problem in an issue
  • open an unfinished pull request as a work in progress (WIP), and explain what you’ve like to get reviewed

How to set up a development environment

  • (Optional) Fork the project on GitHub.

  • Clone the git repository.

  • (Optional) Set up a virtualenv.

  • Install gcovr in development mode, and install the test requirements:

    pip install -e .
    pip install -r requirements.txt

    You can then run gcovr as gcovr or python -m gcovr.

    Run the tests to verify that everything works (see below).

  • (Optional) Install documentation requirements:

    pip install -r doc/requirements.txt

    See doc/README.txt for details on working with the documentation.

  • (Optional) Activate Travis and Appveyor for your forked GitHub repository, so that the cross-platform compatibility tests get run whenever you push your work to your repository. These tests will also be run when you open a pull request to the main gcovr repository.

Tip: If you have problems getting everything set up, consider looking at the .travis.yml (Linux) and appveyor.yml (Windows) files.

On Windows, you will need to install a GCC toolchain as the tests expect a Unix-like environment. You can use MinGW-W64 or MinGW. To run the tests, please make sure that the make and cmake from your MinGW distribution are in the system PATH.

Project Structure

Path Description
/ project root
/gcovr/ the gcovr source code (Python module)
/gcovr/ command line interface + top-level behaviour
/gcovr/templates/ HTML report templates
/gcovr/tests/ unit tests + integration test corpus
/ Python package configuration
/doc/ documentation
/doc/sources/ user guide + website
/doc/examples/ runnable examples for the user guide

The program entrypoint and command line interface is in gcovr/ The coverage data is parsed in the gcovr.gcov module. The HTML, XML, text, and summary reports are in gcovr.html_generator and respective modules.

Test suite

The tests are in the gcovr/tests directory. You can run the tests with python -m pytest.

There are unit tests for some parts of gcovr, and a comprehensive corpus of example projects that are executed as the test. Each gcovr/tests/* directory is one such example project.

Each project in the corpus contains a Makefile and a reference directory. The Makefile controls how the project is built, and how gcovr should be invoked. The reference directory contains baseline files against which the gcovr output is compared. Each project is tested three times to cover txt, html, and xml output.

Because the tests are a bit slow, you can limit the tests to a specific test file, example project, or output format. For example:

# run only XML tests
python -m pytest -k xml

# run the simple1 tests
python -m pytest -k simple1

# run the simple1 tests only for XML
python -m pytest -k 'xml and simple1'

To see all tests, run pytest in -v verbose mode. To see which tests would be run, add the --collect-only option.

The tests currently assume that you are using GCC 5.

Become a gcovr developer

After you’ve contributed a bit (whether with discussions, documentation, or code), consider becoming a gcovr developer. As a developer, you can:

  • manage issues and pull requests (label and close them)
  • review pull requests (a developer must approve each PR before it can be merged)
  • participate in votes

Just open an issue that you’re interested, and we’ll have a quick vote.