# pytest conftest Fixture Dependency Graph & mock.patch Leak Detector

Statically analyze a pytest conftest.py chain: render the fixture dependency graph across all five scopes (function/class/module/package/session), detect deeper-conftest overrides, ScopeMismatch edges, and cross-test state pollution — mock.patch().start() without .stop(), monkeypatch leaking from broad-scope fixtures, and with mock.patch held open across yield.

> Canonical page: https://elysiatools.com/en/tools/pytest-conftest-fixture-dependency-graph-and-mock-patch-leak-detector

- **Category:** Development

- **Keywords:** pytest, conftest, fixture, dependency graph, mock.patch leak, monkeypatch, scope mismatch, session fixture, test pollution, static analysis, python testing, fixture scope

## Overview

Paste one or more conftest.py / test files separated by '# --- file: path ---' markers (or upload a .py). The analyzer implements pytest's documented fixture semantics: scope ordering session > package > module > class > function, ScopeMismatch when a broad fixture depends on a narrower one, and test-outward name resolution where the deepest conftest wins. Leak rules: monkeypatch/capsys/tmp_path are function-scoped built-ins whose undo never runs inside a module/session fixture (patches bleed across the session, pytest-mock issue #84 class of bug); patcher.start() without .stop() survives until process exit; a with mock.patch(...) wrapping a yield keeps every test on the patched target. Output: severity-ranked findings, a fixture inventory table and a scope-layered dependency SVG graph.

## Inputs

- **Python sources (conftest chain)** (textarea): # --- file: conftest.py --- import pytest @pytest.fixture(scope="session") def db(): yield 1 …
- **Python file (optional, .py/.txt)** (file)
- **Show built-in fixture nodes in graph** (checkbox)

## When to use

- Debugging flaky pytest test suites where tests fail depending on execution order due to cross-test state pollution.
- Refactoring multi-directory test suites to audit fixture overrides and verify scope hierarchy across conftest.py files.
- Reviewing pull requests to catch unstopped mock.patch().start() calls or monkeypatch misuse in broad-scope fixtures.

## How it works

- Paste conftest.py and test file contents separated by '# --- file: path ---' markers, or upload a .py file.
- The static analyzer parses fixture definitions, scope annotations, dependencies, and mock or patch operations without running code.
- The tool inspects dependency edges for ScopeMismatch errors, tracks deeper conftest fixture overrides, and checks for unstopped patches.
- Inspect the scope-layered dependency SVG graph, fixture inventory table, and severity-ranked pollution findings.

## Use cases

- Visualizing complex fixture dependency graphs and overrides across multi-tier conftest hierarchies.
- Detecting silent patch leaks where mock.patch().start() survives past test boundaries and corrupts test runs.
- Validating scope hierarchies before upgrading pytest or refactoring shared test utilities.

## Frequently asked questions

### Does this tool execute test code or require a Python runtime?

No. The analyzer performs purely static source code parsing without running tests or importing modules.

### How do I analyze multiple conftest.py files simultaneously?

Separate each file in the source input using '# --- file: path/to/conftest.py ---' header markers.

### Why is using monkeypatch in a module or session fixture flagged?

monkeypatch is function-scoped, so its teardown never runs in broad fixtures, causing patches to leak across tests.

### What triggers a ScopeMismatch error in pytest?

A ScopeMismatch occurs when a broader fixture such as session or module depends on a narrower fixture like function.

### What mock.patch issues does the analyzer detect?

It detects patcher.start() calls without corresponding .stop() calls and flags with mock.patch held open across yields.

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