Introduction to Fixtures

What Are Fixtures?

Fixtures are pytest's answer to setup and teardown. They provide a clean, modular way to prepare test data, set up resources, and clean up after tests finish. Instead of repeating setup code in every test, you define it once in a fixture.

Basic Fixture

A fixture is a function decorated with @pytest.fixture. It can set up data, create objects, or establish connections:

import pytest

@pytest.fixture
def sample_user():
    return {
        "name": "Alice",
        "email": "alice@example.com",
        "age": 30
    }

def test_user_name(sample_user):
    assert sample_user["name"] == "Alice"

def test_user_email(sample_user):
    assert sample_user["email"] == "alice@example.com"

pytest automatically detects that sample_user is a fixture and passes the fixture's return value to the test function.

Why Fixtures Are Better Than Setup

Compare these approaches:

# Without fixtures - repetitive setup
def get_user():
    return {"name": "Alice", "email": "alice@example.com"}

def test_user_name():
    user = get_user()
    assert user["name"] == "Alice"

def test_user_email():
    user = get_user()  # duplicated!
    assert user["email"] == "alice@example.com"

# With fixtures - clean and DRY
@pytest.fixture
def user():
    return {"name": "Alice", "email": "alice@example.com"}

def test_user_name(user):
    assert user["name"] == "Alice"

def test_user_email(user):
    assert user["email"] == "alice@example.com"

Fixture Naming

Fixture names are the parameter names of your test functions. pytest matches them automatically:

@pytest.fixture
def database_connection():
    conn = create_connection()
    yield conn
    conn.close()

# The parameter name MUST match the fixture name
def test_query(database_connection):
    result = database_connection.execute("SELECT 1")
    assert result is not None