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Pytest

The Pytest module runs your Python tests with Pytest, the same way locally, in CI, and in Dagger Cloud. It discovers Python projects in your workspace. It can use a custom Python container when the default environment is not enough.

Add it to your workspace​

dagger module install dagger.io/python/pytest

Run the tests​

dagger check                 # run every check in the workspace
dagger check pytest:test-all # run Pytest against the selected projects

pytest:test-all injects pytest_otel automatically, so individual Python tests appear as spans in the Dagger TUI and Dagger Cloud with no project changes. The module uses uv to install the project dependencies, pytest, and pytest_otel together.

Test options​

The pytest:test-all check uses the module settings:

  • version (default 3.14) is the Python version the default container provisions, such as 3.13 or 3.12. It cannot be combined with a custom base.
  • args (default ["-v"]) are arguments passed straight to pytest, such as ["-x", "--tb=short"].

Keep this module focused on tests; use separate modules for formatting, linting, shell scripts, or generated files.

Configure it​

List the current settings and their values with dagger module settings pytest, then set one with dagger module settings pytest <key> <value>. Settings are stored in dagger.toml under [modules.pytest.settings]:

  • scope (default: ["**"]) selects project roots to test. Paths are relative to the workspace root.
  • base (default: none) is a custom container that already has Python and uv installed. Set it when tests need system packages, a private index, or other tools.
[modules.pytest.settings]
scope = ["service"]

Working with other modules​

This module is a good first check for Python repos. Once it passes locally, it is a natural candidate for autocheck and PR validation.

source code