pytest-find-dependencies

0.6.0 · active · verified Sat Apr 11

A pytest plugin designed to automatically identify dependencies between tests. It achieves this by running tests in various sequences (forward and backward) and employing a binary search algorithm to pinpoint which tests rely on others. This can help uncover hidden state-based dependencies that lead to flaky tests. The current version is 0.6.0 and it is actively maintained.

Warnings

gotcha The plugin's author suggests considering `detect-test-pollution` as an alternative, noting its superior documentation and greater popularity.
Fix: Evaluate `detect-test-pollution` alongside `pytest-find-dependencies` for your use case.
gotcha When `pytest-xdist` (a plugin for parallel test execution) is detected, `pytest-find-dependencies` ensures that its internal dependency-finding test runs are not distributed. This is to prevent breaking the dependency check mechanism.
Fix: No specific user action is required; this is handled internally by the plugin to maintain correctness.
gotcha By default, the dependency analysis run returns an exit code of 1 if *any* dependency is found, even if all tests pass. If you want the exit code to reflect actual test failures, use the `--fail-on-failed-tests` option.
Fix: Add `--fail-on-failed-tests` to your pytest command if you want failing tests to also cause a non-zero exit code.
gotcha Dependencies that stem from a permanent change in the test environment (e.g., a resource being permanently altered) will only be found if the test causing the change runs *before* the dependent test during the plugin's analysis.
Fix: Be aware of this limitation; some types of environment-altering dependencies might be missed depending on the initial test ordering.
gotcha If you use other plugins that change test order (e.g., `pytest-order`), their ordering rules will only apply to the *first* test run during dependency analysis. Subsequent runs by `pytest-find-dependencies` for dependency isolation will define their own order.
Fix: Consider using the `--markers-to-ignore` option to exclude tests with specific ordering markers if you want them explicitly outside the dependency analysis.

Install

pip install pytest-find-dependencies Install from PyPI

Imports

pytest-find-dependencies

This plugin is primarily activated via the pytest command-line interface using the `--find-dependencies` option. Direct Python imports into user test files for its core functionality are not typical.

The functionality is accessed through the pytest CLI, not direct Python imports.

Quickstart

To use `pytest-find-dependencies`, install it and then run `pytest` with the `--find-dependencies` option. The plugin will automatically analyze your tests and report any identified dependencies. The example demonstrates a logical dependency via a shared mutable state, which the plugin should detect.

import pytest

# Simulate a shared state that might be modified by one test and read by another
_shared_state = {'value': 0}

def test_setup_value():
    """This test sets a value in the shared state."""
    _shared_state['value'] = 10
    assert True

def test_use_value():
    """This test depends on the value being set by test_setup_value."""
    assert _shared_state['value'] == 10

def test_independent():
    """An independent test with no dependencies."""
    assert 1 + 1 == 2

# To run this example, save it as `test_dependencies.py` and execute:
# pytest --find-dependencies test_dependencies.py
# The output should indicate a dependency found between 'test_use_value' and 'test_setup_value'.

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