Fixtures

Pytest · Reference cheat sheet

📋 Overview

Fixtures provide setup/teardown via dependency injection. Tests request fixtures by parameter name; scopes control lifetime (function, class, module, package, session).

🔧 Core concepts

Concept	Meaning
`@pytest.fixture`	Define reusable resource
`yield`	Setup before, teardown after
`scope`	How often to recreate
`autouse`	Apply without requesting
`params`	Parametrized fixture
Fixture factory	Return a creator callable

Prefer fixtures over setup/teardown methods for composability.

💡 Examples

Basic yield fixture:

import pytest

@pytest.fixture
def db():
    conn = connect()
    yield conn
    conn.close()

def test_query(db):
    assert db.execute("SELECT 1").fetchone()[0] == 1

Scopes:

@pytest.fixture(scope="session")
def app():
    return create_app()

@pytest.fixture(scope="module")
def client(app):
    return app.test_client()

Factory:

@pytest.fixture
def make_user(db):
    created = []
    def _make(**kwargs):
        u = User(**kwargs)
        db.add(u)
        created.append(u)
        return u
    yield _make
    for u in created:
        db.delete(u)

Autouse:

@pytest.fixture(autouse=True)
def _fast_cache(monkeypatch):
    monkeypatch.setenv("CACHE_URL", "memory://")

⚠️ Pitfalls

Session-scoped mutable state leaking between tests.
Requesting heavy fixtures unnecessarily — keep scopes tight.
Using return when teardown is needed — use yield.
Circular fixture dependencies.
Overusing autouse — hard to see what a test depends on.

Fixtures

Fixtures

📋 Overview

🔧 Core concepts

💡 Examples

⚠️ Pitfalls

🔗 Related

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