Feel free and welcome to contribute to this project. You can start with filing issues and ideas for improvement in GitHub tracker. Our favorite thoughts from The Zen of Python:

  • Beautiful is better than ugly.

  • Simple is better than complex.

  • Readability counts.

We respect the PEP8 Style Guide for Python Code. Here’s a couple of recommendations to keep on mind when writing code:

  • Maximum line length is 99 for code and 72 for documentation.

  • Comments should be complete sentences.

  • The first word should be capitalized (unless identifier).

  • When using hanging indent, the first line should be empty.

  • The closing brace/bracket/parenthesis on multiline constructs is under the first non-whitespace character of the last line.

When generating user messages use the whole sentence with the first word capitalized and enclose any names in single quotes:

self.warn(f"File '{path}' not found.")


It is challenging to be both concise and descriptive, but that is what a well-written summary should do. Consider the commit message as something that will be pasted into release notes:

  • The first line should have up to 50 characters.

  • Complete sentence with the first word capitalized.

  • Should concisely describe the purpose of the patch.

  • Do not prefix the message with file or module names.

  • Other details should be separated by a blank line.

Why should I care?

  • It helps others (and yourself) find relevant commits quickly.

  • The summary line will be re-used later (e.g. for rpm changelog).

  • Some tools do not handle wrapping, so it is then hard to read.

  • You will make the maintainers happy to read beautiful commits :)

You can get some more context in the stackoverflow article.


In order to experiment, play with the latest bits and develop improvements it is best to use a virtual environment. Make sure that you have all required packages installed on your box:

make develop

Create a development virtual environment with hatch:

git clone
cd tmt
hatch env create dev

Enter the environment by running:

hatch -e dev shell

When interacting from within the development environment with services with internal certificates, you need to export the following environment variable:

export REQUESTS_CA_BUNDLE=/etc/pki/tls/certs/ca-bundle.crt

Install the pre-commit script to run all available checks for your commits to the project:

pre-commit install


Every code change should be accompanied by tests covering the new feature or affected code area. It’s possible to write new tests or extend the existing ones.

If writing a test is not feasible for you, explain the reason in the pull request. If possible, the maintainers will help with creating needed test coverage. You might also want to add the help wanted and tests needed labels to bring a bit more attention to your pull request.

Run the default set of tests directly on your localhost:

tmt run

Run selected tests or plans in verbose mode:

tmt run --verbose plan --name basic
tmt run -v test -n smoke

Unit Tests

To run unit tests in hatch environment using pytest and generate coverage report:

make coverage

To see all available scripts for running tests in hatch test virtual environments:

hatch env show test

To run ‘unit’ script for example, run:

hatch run test:unit

When running tests using hatch, there are multiple virtual environments available, each using a different Python interpreter (generally the lowest and highest version supported). To run the tests in all environments, install the required Python versions. For example:

dnf install python3.9 python3.11


When adding new unit tests, do not create class-based tests derived from unittest.TestCase class. Such classes do not play well with Pytest’s fixtures, see for details.

Provision Methods

Tests which exercise multiple provision methods should use the PROVISION_HOW environment variable to select which provision method should be exercised during their execution. This variable is likely to have local set as the default value in the test script to execute directly on the test runner as the default scenario. If a test does not support the local provision method make sure to use the provision-only tag so that the test in question is excluded from the regular plans.

The following tags can be used to enable given test under the respective provision method plan:


For tests checking the artemis plugin functionality.


For tests checking the beaker plugin functionality using the mrack plugin.


For tests checking the connect plugin functionality.


For tests checking the container provision method using the podman plugin.


For tests checking the virtual provision method using the testcloud plugin.


Tests which are not tied to a specific provision method but should be executed for all provision methods which are using ssh to connect to guests.


Used to mark tests which are suitable to be run only under specific provision methods. These will be excluded from regular plans.


In addition to the tags related to the Provision Methods tags, following are used in the tests:


Test has to be executed as the root (or privileged) user to execute properly. For example test adds user, changes the system, etc.


Test integration of BeakerLib framework with the tmt.


Test using requre to mock connections to other servers.


Tests which exercise the container provisioning plugin with various guest environments should use the custom-built set of container images rather than using the upstream ones directly. We built custom images to have better control over the initial environment setup, especially when it comes to essential requirements and assumption tmt makes about the guest setup. The naming scheme also provides better information about content of these images when compared to very varied upstream locations.

Naming scheme

All our test images follow a simple naming pattern:



To make it clear the image was built locally, it is owned by tmt, and it is not packaging tmt but serves for testing purposes only.


There are various kinds of “images”, the most well-known ones would be Docker/Podman images, their names would contain container flag, and QCOW2 images for VMs which would be labeled with virtual.


A lower-cased name of the Linux distribution hosted in the image: fedora, ubuntu, alpine, etc.


A release of the DISTRIBUTION: 7 for CentOS 7, stream9 for CentOS Stream 9, or 40, rawhide and even coreos for Fedora.


Additional flags describing a “flavor” of the image:

  • upstream images are identical to an upstream image, adding no special setup on top of the upstream.

  • unprivileged images come with password-less sudo setup and may be used when unprivileged access is part of the test.

  • ostree images are Fedora CoreOS that simulate being deployed by ostree.


Usually latest as in “the latest image for this distro, release and extra flags”.


So far we do not have much use for other tags besides latest. stable used for Fedora CoreOS images will probably go away in favor of latest.

For example, the following images can be found:

# Latest Alpine, with added Bash to simulate proper essential setup:

# Various CentOS releases:

# Fedora rawhide, with dnf5 pre-installed:

# Same, but with password-less sudo set up:

To build these images, run the following:

# Build all images...
make images-tests

# ... or just a single one:
make images-tests/tmt/tests/container/fedora/rawhide:latest

Tests that need to use various container images should trigger this command before running the actual test cases:

rlRun "make -C images-tests"

To list built container images, run the following:

podman images | grep 'localhost/tmt/tests/' | sort

To remove these images from your local system, run the following:

make clean-test-images


When submitting a change affecting user experience it’s always good to include respective documentation. You can add or update the Metadata Specification, extend the Examples or write a new chapter for the user Guide.

By default, examples provided in the specification stories are rendered as yaml. In order to select a different syntax highlighting schema add # syntax: <format>, for example:

# syntax: shell

Building documentation is then quite straightforward:

make docs

Find the resulting html pages under the docs/_build/html folder.

Use the TMT_DOCS_THEME variable to easily pick custom theme. If specified, make docs would use this theme for documentation rendering by Sphinx. The theme must be installed manually, make docs will not do so. Variable expects two strings, separated by a colon (:): theme package name, and theme name.

# Sphinx book theme, sphinx-book-theme:
TMT_DOCS_THEME="sphinx_book_theme:sphinx_book_theme" make docs

# Renku theme, renku-sphinx-theme - note that package name
# and theme name are *not* the same string:
TMT_DOCS_THEME="renku_sphinx_theme:renku" make docs

Pull Requests

When submitting a new pull request which is not completely ready for merging but you would like to get an early feedback on the concept, use the GitHub feature to mark it as a Draft rather than using the WIP prefix in the summary.

During the pull request review it is recommended to add new commits with your changes on the top of the branch instead of amending the original commit and doing a force push. This will make it easier for the reviewers to see what has recently changed.

Once the pull request has been successfully reviewed and all tests passed, please rebase on the latest main branch content and squash the changes into a single commit. Use multiple commits to group relevant code changes if the pull request is too large for a single commit.

If the pull request addresses an existing issue, mention it using one of the automatically parsed formats so that it is linked to it, for example:

Fix #1234.

By default only a core set of tests is executed against a newly created pull request and its updates to verify basic sanity of the change. Once the pull request content is ready for a thorough testing add the full test label and make sure that the discuss label is not present. All future changes of the pull request will be tested with the full test coverage. For changes related to documentation only the full test suite is not required.


The following checklist template is automatically added to the new pull request description to easily track progress of the implementation and prevent forgetting about essential steps to be completed before it is merged. Feel free to remove those which are irrelevant for your change.

Pull Request Checklist

* [ ] implement the feature
* [ ] write the documentation
* [ ] extend the test coverage
* [ ] update the specification
* [ ] adjust plugin docstring
* [ ] modify the json schema
* [ ] mention the version
* [ ] include a release note

The version should be mentioned in the specification and a release note should be included when a new essential feature is added or an important change is introduced so that users can easily check whether given functionality is already available in their package:

.. versionadded:: 1.23


Code review is an essential part of the workflow. It ensures good quality of the code and prevents introducing regressions, but it also brings some additional benefits: By reading code written by others you can learn new stuff and get inspired for your own code. Each completed pull request review helps you, little by little, to get familiar with larger part of the project code and empowers you to contribute more easily in the future.

For instructions how to locally try a change on your laptop see the Develop section. Basically just enable the development environment and check out the pull request branch or use the github cli to check out code from a fork repository:

hatch -e dev shell         # enable the dev environment
git checkout the-feature   # if branch is in the tmt repo
gh pr checkout 1234        # check out branch from a fork

It is also possible to directly install packages freshly built by Packit for given pull request. See the respective Packit check for detailed installation instructions.

Note that you don’t have to always read the whole change. There are several ways how to provide feedback on the pull request:

  • check how the documentation would be rendered in the docs/ pull request check, look for typos, identify wording which is confusing or not clear, point out that documentation is completely missing for some area

  • remind a forgotten item from the Checklist, for example suggest writing a release note for a new significant feature which should be highlighted to users

  • verify just the functionality, make sure it works as expected and confirm it in a short comment, provide a simple reproducer when something is broken

  • review only the newly added test case, verify that the test works as expected and properly verifies the functionality

Even partial review which happens sooner is beneficial, saves time. Every single comment helps to improve and move the project forward. No question is a dumb question. Every feedback counts!


Pull request merging is done by one of maintainers who have a good overview of the whole code. Maintainer who will take care of the process will assign themselves to the pull request. Before merging it’s good to check the following:

  • New test coverage added if appropriate, all tests passed

  • Documentation has been added or updated where appropriate

  • Commit messages are sane, commits are reasonably squashed

  • At least one positive review provided by the maintainers

  • Merge commits are not used, rebase on the main instead

Pull requests which should not or cannot be merged are marked with the blocked label. For complex topics which need more eyes to review and discuss before merging use the discuss label.


There are several Makefile targets defined to make the common daily tasks easy & efficient:

make test

Execute the unit test suite.

make smoke

Perform quick basic functionality test.

make coverage

Run the test suite under coverage and report results.

make docs

Build documentation.

make packages

Build rpm and srpm packages.

make images

Build container images.

make tags

Create or update the Vim tags file for quick searching. You might want to use set tags=./tags; in your .vimrc to enable parent directory search for the tags file as well.

make clean

Cleanup all temporary files.


Follow the steps below to create a new major or minor release:

  • Use git log --oneline --no-decorate x.y-1.. to generate the changelog

  • Update overview.rst with new contributors since the last release

  • Review the release notes in releases.rst, update as needed

  • Add a Release tmt-x.y.0 commit with the specfile update

  • Create a pull request with the commit, ensure tests pass, merge it

Release a new package to Fedora and EPEL repositories:

  • Move the fedora branch to point to the new release

  • Tag the commit with x.y.0, push tags git push --tags

  • Create a new github release based on the tag above

  • Check Fedora pull requests, make sure tests pass and merge

Finally, if everything went well:

  • Close the corresponding release milestone

  • Once the non development copr build is completed, move the quay branch to point to the release commit as well to build fresh container images.

Handle manually what did not went well:

  • If the automation triggered by publishing the new github release was not successful, publish the fresh code to the pypi repository manually using make wheel && make upload

  • If there was a problem with creating Fedora pull requests, you can trigger them manually using /packit propose-downstream in any open issue.