Pytest Dagger Toolchain

A toolchain for testing Python application with automatic OpenTelemetry tracing

This toolchain automatically injects a pytest_otel library for test tracing visibility in Dagger TUI and Dagger Cloud. No configuration required.

Usage:

On a python project, using pytest as the test runner:

• initialize a dagger module if not already done: dagger init .
• install the pytest toolchain: dagger toolchain install github.com/dagger/pytest
• run tests: dagger check pytest:test. It will:
  • creates an Alpine based container with uv (a uv cache volume is set)
  • prepares Python for the requested version via uv, failing fast if it can't be resolved
  • injects the pytest_otel dependency for automatic test tracing (before your source is added, so it stays cached)
  • installs your project dependencies (automatically via uv run for pyproject.toml projects, or from requirements.txt)
  • export captured stdout, stderr, and Python logging records as OTel logs
  • run pytest

By default the toolchain builds an Alpine + uv container. You can instead provide your own container (with Python and uv installed); the toolchain reuses its existing virtual environment at /opt/venv rather than recreating it.

Example, using fastly/fastly-cli:

$ git clone github.com/fastly/fastly-cli

$ cd fastly-cli

$ # Initialize an empty dagger module
$ dagger init

Initialized module fastapi-cli in ~/dev/src/github.com/fastapi/fastapi-cli

$ # Add the pytest toolchain
$ dagger toolchain install github.com/dagger/pytest

toolchain installed

$ # Run tests, with tracing enabled
$ dagger check
✔ pytest:test 17.4s ⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣧⣿⣿⣿⣿⣿⣿⣿⡆⡄⣿⣿⡄ OK