> ## Documentation Index
> Fetch the complete documentation index at: https://docs.featherframework.org/llms.txt
> Use this file to discover all available pages before exploring further.

# Testing patterns

> What to assert at each layer: HTTP behaviour in route tests, business rules in service tests, defaults in model tests.

<Tabs>
  <Tab title="Route tests">
    Test HTTP behaviour — status codes, auth gates, response shape.

    ```python theme={null}
    def test_list_items_requires_auth(client):
        response = client.get('/api/items')
        assert response.status_code == 401

    def test_list_items_when_authenticated(csrf_client, authenticated_user):
        response = csrf_client.get('/api/items')
        assert response.status_code == 200
        assert 'items' in response.json
    ```
  </Tab>

  <Tab title="Service tests">
    Test business logic directly, without going through HTTP.

    ```python theme={null}
    from services import ItemService
    from feather.exceptions import ValidationError
    import pytest

    def test_create_item_validates_name(app):
        with app.app_context():
            service = ItemService()
            with pytest.raises(ValidationError):
                service.create(name='')   # empty name should fail

    def test_create_item_success(app):
        with app.app_context():
            service = ItemService()
            item = service.create(name='Valid Name')
            assert item.id is not None
    ```
  </Tab>

  <Tab title="Model tests">
    Test the data layer — mixin behaviour, defaults, constraints.

    ```python theme={null}
    def test_item_defaults(app):
        with app.app_context():
            item = Item(name='Test')
            db.session.add(item)
            db.session.commit()

            assert item.id is not None
            assert item.created_at is not None
    ```
  </Tab>
</Tabs>

<Tip>
  Because routes stay thin and services hold the logic, most of your assertions belong in
  service tests. Route tests then only need to prove the wiring: the right decorator, the
  right status code, the right key in the response.
</Tip>