pytest-testing

name	pytest-testing
description	Guide for writing pytest tests following this project's patterns including fixtures, mocking, and test organization.

Pytest Testing

Use this skill when writing tests for this FastAPI application. Follow these patterns for consistency.

For comprehensive testing guidelines, see tests/AGENTS.md.

Test Organization

Category	Path	Focus
Unit	tests/unit/	Models, config, services, middleware
Integration	tests/integration/	API routes with mocked services
E2E	tests/e2e/	Real Firebase emulator tests

Additional directories:

• tests/helpers/ - Factory functions, auth helpers, assertion utilities
• tests/mocks/ - Fake Firestore client, Firebase mocks, service stubs

Mirror the app/ structure in test directories.

Unit vs Integration vs E2E: The Simple Rule

If your test uses the client fixture (real app TestClient), it's an integration test. If your test uses Firebase emulators, it's an E2E test. Everything else is a unit test.

Criterion	Unit Test	Integration Test	E2E Test
Uses client fixture?	No	Yes	Yes
Mocks ProfileService?	N/A	Yes	No
Uses real Firestore?	No	No	Yes (emulator)
Included in CI?	Yes	Yes	No

Integration Test Pattern

Integration tests use the FastAPI TestClient with mocked services via tests/integration/conftest.py:

"""
Integration tests for resource endpoints.
"""

from unittest.mock import AsyncMock

import pytest
from fastapi.testclient import TestClient

from app.exceptions import ResourceAlreadyExistsError, ResourceNotFoundError
from tests.helpers.resources import make_resource, make_resource_payload_dict

BASE_URL = "/v1/resource"


class TestCreateResource:
    """
    Tests for POST /v1/resource.
    """

    def test_returns_201_on_success(
        self,
        client: TestClient,
        with_fake_user: None,
        mock_resource_service: AsyncMock,
    ) -> None:
        """
        Verify successful resource creation returns 201.
        """
        mock_resource_service.create_resource.return_value = make_resource()

        response = client.post(BASE_URL, json=make_resource_payload_dict())

        assert response.status_code == 201
        assert "Location" in response.headers
        mock_resource_service.create_resource.assert_awaited_once()

    def test_returns_409_when_duplicate(
        self,
        client: TestClient,
        with_fake_user: None,
        mock_resource_service: AsyncMock,
    ) -> None:
        """
        Verify duplicate resource returns 409 Conflict.
        """
        mock_resource_service.create_resource.side_effect = ResourceAlreadyExistsError()

        response = client.post(BASE_URL, json=make_resource_payload_dict())

        assert response.status_code == 409
        body = response.json()
        assert body["title"] == 

     () -> :
        
        response = client.post(BASE_URL, json=make_resource_payload_dict())

         response.status_code == 

Integration Fixtures

The tests/integration/conftest.py provides:

• client - TestClient with mocked services injected via dependency_overrides
• fake_user - Simple fake FirebaseUser
• with_fake_user - Override auth dependency to return fake user
• mock_resource_service - AsyncMock of service for assertion

# tests/integration/conftest.py
@pytest.fixture
def mock_resource_service() -> AsyncMock:
    """
    Mocked ResourceService for integration tests.
    """
    return AsyncMock(spec=ResourceService)


@pytest.fixture
def client(mock_resource_service: AsyncMock) -> Generator[TestClient]:
    """
    TestClient with mocked services (no Firebase/Firestore).
    """
    from app.main import app

    with (
        patch("app.main.initialize_firebase"),
        patch("app.main.setup_logging"),
        patch("app.main.close_async_firestore_client"),
    ):
        app.dependency_overrides[get_resource_service] = lambda: mock_resource_service
        with TestClient(app, raise_server_exceptions=False) as c:
            yield c
        app.dependency_overrides.clear()


@pytest.fixture
def with_fake_user(fake_user: FirebaseUser) -> Generator[None]:
    """
    Override auth to return fake user.
    """
    from app.main import app

    app.dependency_overrides[verify_firebase_token] = lambda: fake_user
    yield
    app.dependency_overrides.pop(verify_firebase_token, None)

Helper Functions

Create factory functions in tests/helpers/:

# tests/helpers/resources.py
from datetime import UTC, datetime

from app.models.resource import Resource, ResourceCreate


def make_resource(
    resource_id: str = "test-resource-123",
    **kwargs: object,
) -> Resource:
    """
    Create a Resource instance for testing.
    """
    now = datetime.now(UTC)
    base = {
        "name": "Test Resource",
        "active": True,
        "created_at": now,
        "updated_at": now,
    }
    return Resource(id=resource_id, **{**base, **kwargs})


def make_resource_payload_dict(
    *,
    overrides: dict[str, object] | None = None,
    omit: list[str] | None = None,
) -> dict[str, object]:
    """
    Build a plain dict payload for POST/PUT requests.
    """
    payload: dict[str, object] = {
        "name": "Test Resource",
        "active": True,
    }
    if overrides:
        payload.update(overrides)
    if omit:
        for key in omit:
            payload.pop(key, )
     payload

Parametrized Tests

Use @pytest.mark.parametrize for data-driven tests:

@pytest.mark.parametrize(
    "missing_field",
    ["name", "email", "phone_number"],
)
def test_returns_422_for_missing_fields(
    self,
    client: TestClient,
    with_fake_user: None,
    missing_field: str,
) -> None:
    """
    Verify missing required fields return 422.
    """
    payload = make_resource_payload_dict(omit=[missing_field])

    response = client.post(BASE_URL, json=payload)

    assert response.status_code == 422

Async Tests

With asyncio_mode = "auto" in pyproject.toml, no decorator is needed:

async def test_async_operation() -> None:
    """
    Async test runs automatically without @pytest.mark.asyncio.
    """
    result = await some_async_function()
    assert result is not None

Mocking Patterns

Use pytest-mock (mocker fixture) for patching:

def test_with_mock(mocker: MockerFixture) -> None:
    mock_client = mocker.patch("app.services.resource.get_async_firestore_client")
    mock_client.return_value = FakeAsyncClient()
    # ... test code

Use monkeypatch for environment variables:

def test_with_env(monkeypatch: pytest.MonkeyPatch) -> None:
    monkeypatch.setenv("DEBUG", "true")
    get_settings.cache_clear()
    # ... test code

Test Naming

Pattern: test_<what>_<condition/scenario>

def test_create_resource_returns_201_on_success() -> None: ...
def test_get_resource_returns_404_when_not_found() -> None: ...
def test_update_resource_with_invalid_email_returns_422() -> None: ...

URL Conventions

Always use paths without trailing slashes to match routes:

# Correct - use versioned path without trailing slash
response = client.get("/v1/resource")

# Wrong - trailing slash returns 404 (redirect_slashes=False)
response = client.get("/v1/resource/")

HTTP Mocking with pytest-httpx

Use the httpx_mock fixture to mock outbound HTTP requests:

from pytest_httpx import HTTPXMock

def test_outbound_call(httpx_mock: HTTPXMock) -> None:
    httpx_mock.add_response(
        method="GET",
        url="https://example.com/api/status",
        json={"ok": True},
        status_code=200,
    )

    resp = httpx.get("https://example.com/api/status")
    assert resp.json() == {"ok": True}

Fake Firestore for Unit Tests

Use tests/mocks/firestore.py for service unit tests:

from pytest_mock import MockerFixture
from tests.mocks.firestore import FakeAsyncClient

@pytest.fixture
def fake_db(mocker: MockerFixture) -> FakeAsyncClient:
    db = FakeAsyncClient()
    mocker.patch("app.services.resource.get_async_firestore_client", return_value=db)
    return db


class TestResourceServiceGetResource:
    async def test_returns_resource_when_exists(self, fake_db: FakeAsyncClient) -> None:
        fake_db._store["user-123"] = _make_resource_data(user_id="user-123")
        service = ResourceService()
        resource = await service.get_resource("user-123")
        assert resource.id == "user-123"

Running Tests

just test               # Unit + integration (CI-compatible)
just test-unit          # Unit tests only
just test-integration   # Integration tests only
just test-e2e           # E2E tests (requires: just emulators)
just cov                # Coverage report