Parameterized Fixtures

Parameterized Fixtures

Sometimes you want to run the same test with different inputs. Parameterized fixtures let you provide multiple sets of data using the params argument.

Basic Parameterization

import pytest

@pytest.fixture(params=[1, 2, 3, 4, 5])
def number(request):
    return request.param

def test_is_positive(number):
    assert number > 0

# This test runs 5 times, once for each parameter
# test_is_positive[1], test_is_positive[2], etc.

Multiple Parameter Sets

You can parameterize with complex data structures:

@pytest.fixture(params=[
    {"input": "hello", "expected": "HELLO"},
    {"input": "world", "expected": "WORLD"},
    {"input": "", "expected": ""},
])
def string_data(request):
    return request.param

def test_upper(string_data):
    assert string_data["input"].upper() == string_data["expected"]

Named Parameters with IDs

Use the ids argument to give readable names to each parameter set:

@pytest.fixture(
    params=[0, 1, -1, 100],
    ids=["zero", "positive", "negative", "large"]
)
def number(request):
    return request.param

def test_abs(number):
    assert abs(number) >= 0

# Output: test_abs[zero], test_abs[positive], test_abs[negative], test_abs[large]

Combining Fixtures

Parameterized fixtures can depend on other fixtures:

@pytest.fixture(params=["sqlite", "postgres"])
def db_engine(request):
    return create_engine(request.param)

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

def test_query(database):
    result = database.execute("SELECT 1")
    assert result.fetchone()

The database fixture runs once for each db_engine parameter.