pytest-just

A pytest plugin for testing justfiles.

Package status

pytest-just is published on PyPI.

• PyPI: https://pypi.org/project/pytest-just/
• Source: https://github.com/DataBooth/pytest-just
• Latest release notes: RELEASE_NOTES.md

What is pytest-just?

pytest-just is a plugin that adds a session-scoped just fixture to pytest so you can test justfile contracts directly in your test suite.

It is designed for assertions about recipe structure and intent, including:

• recipe existence
• dependency relationships
• parameter contracts
• rendered body content
• alias and assignment mapping

Why use pytest-just?

As projects grow, justfile automation often becomes critical but under-tested. Small recipe changes can quietly break CI, local developer workflows, or release steps. In plain terms: just keeps repeatable team tasks in one place, and pytest-just makes sure those tasks keep working as the project changes.

pytest-just helps by making contract checks:

• fast
• repeatable
• easy to run in CI
• explicit in code review

This catches automation drift early without requiring full end-to-end execution of every command.

Tooling

• Package and commands: uv
• Lint/format checks: ruff
• Type checks: ty
• Logging: loguru

Install from PyPI

Add pytest-just to your test dependencies:

uv add --dev pytest-just

You also need the just binary available in your environment:

just --version

Quick start (package usage)

Create tests that use the plugin fixture:

import pytest

@pytest.mark.justfile
def test_ci_depends_on_test(just):
    just.assert_exists("ci")
    just.assert_depends_on("ci", ["test"], transitive=True)

Run:

uv run pytest -q

How does pytest-just work?

pytest-just primarily validates recipe contracts instead of running full recipe side effects. It asks just for structured metadata and rendered recipe text:

• just --dump --dump-format json for recipe graph, parameters, attributes, aliases, and assignments
• just --show <recipe> for rendered body text checks
• just --dry-run <recipe> for safe command smoke checks This keeps tests fast and mostly side-effect free while still validating real justfile behaviour.

Plugin behaviour

The plugin registers:

• a session-scoped just fixture (JustfileFixture)
• a justfile marker

CLI options:

• --justfile-root: directory containing justfile/Justfile (auto-discovered by default)
• --just-bin: path or name of the just binary (default: just)

Auto-discovery walks upwards from pytest root until it finds justfile or Justfile.

API summary (JustfileFixture)

Primary accessors:

• recipe_names(include_private=False)
• dependencies(recipe)
• parameters(recipe) / parameter_names(recipe)
• is_shebang(recipe) / is_private(recipe)
• doc(recipe) / body(recipe) / show(recipe)
• assignments() / aliases()

Assertions:

• assert_exists(recipe)
• assert_depends_on(recipe, expected, transitive=False)
• assert_parameter(recipe, parameter)
• assert_body_contains(recipe, text)
• assert_not_shebang(recipe)
• assert_variable_referenced(recipe, variable)

Execution support:

• dry_run(recipe, *args, env=None) returns subprocess.CompletedProcess[str]

Example usage

import pytest

@pytest.mark.justfile
def test_ci_depends_on_test(just):
    just.assert_exists("ci")
    just.assert_depends_on("ci", ["test"], transitive=True)

Example justfiles for development

Sample real-world-inspired justfiles live under examples/public/ and include:

• dependency chains
• private recipes
• parameterised recipes
• shebang recipes
• imported justfiles

Use them to exercise fixture behaviour while developing the plugin.

Development workflow

If you are contributing to this repository:

uv sync --extra dev
uv run ruff check .
uv run ty check
uv run pytest -q

Property-based testing (Hypothesis)

The test suite includes property-based tests using hypothesis to stress stable invariants such as:

• justfile root discovery across varying directory depth
• body normalisation idempotence
• recipe signature order invariance
• alias and assignment mapping round-trip behaviour

Run only property tests:

uv run pytest -q tests/test_hypothesis_properties.py

Show Hypothesis run statistics:

uv run pytest -q --hypothesis-show-statistics

CI

GitHub Actions runs on pull requests and pushes to main, executing:

• uv run ruff check .
• uv run ty check
• uv run pytest -q --hypothesis-show-statistics