5.6Environment Parameterization

Your test suite must run against any environment with a single configuration change.

# conftest.py
import os
import pytest

@pytest.fixture(scope="session")
def base_url():
    return os.environ.get("API_BASE_URL", "http://localhost:3000/api/v1")

# Run against different environments
API_BASE_URL=http://localhost:3000/api/v1 pytest tests/api/
API_BASE_URL=https://api.staging.example.com/v1 pytest tests/api/
API_BASE_URL=https://api.example.com/v1 pytest tests/api/ -m "readonly"

Best Practices

Practice	Why
Environment variables for secrets	Never commit tokens to source control
Default to localhost	Tests run without configuration out of the box
Tag destructive tests	Exclude create/modify tests from production runs
Use .env files for local development	Keep local config out of command line
Different credentials per environment	Staging admin != production admin

Marking Tests for Environment Safety

@pytest.mark.readonly
def test_list_users(api):
    """Safe to run against production — only reads data."""
    r = api.get("/users")
    assert r.status_code == 200

@pytest.mark.destructive
def test_delete_user(api, create_user):
    """Not safe for production — modifies data."""
    user = create_user()
    r = api.delete(f"/users/{user['id']}")
    assert r.status_code == 204

# pytest.ini
[pytest]
markers =
    readonly: Tests that only read data (safe for production)
    destructive: Tests that create, modify, or delete data
    smoke: Quick health check tests