# Usando Dataclasses { #using-dataclasses }

FastAPI está construido sobre **Pydantic**, y te he estado mostrando cómo usar modelos de Pydantic para declarar requests y responses.

Pero FastAPI también soporta el uso de <a href="https://docs.python.org/3/library/dataclasses.html" class="external-link" target="_blank">`dataclasses`</a> de la misma manera:

{* ../../docs_src/dataclasses_/tutorial001_py310.py hl[1,6:11,18:19] *}

def test_header_param_model(client: TestClient):
    response = client.get(
        "/items/",
        headers=[
            ("save-data", "true"),
            ("if-modified-since", "yesterday"),
            ("traceparent", "123"),
            ("x-tag", "one"),
            ("x-tag", "two"),
        ],
    )
    assert response.status_code == 200, response.text
    assert response.json() == {
        "host": "testserver",

    }


def test_query_param_model_defaults(client: TestClient):
    response = client.get("/items/")
    assert response.status_code == 200
    assert response.json() == {
        "limit": 100,
        "offset": 0,
        "order_by": "created_at",
        "tags": [],
    }


def test_query_param_model_invalid(client: TestClient):
    response = client.get(
        "/items/",
        params={
            "limit": 150,

	if err != nil {
		return false, err
	}

	// Handle large OPA responses when OPA URL is of
	// form http://localhost:8181/v1/data/httpapi/authz
	type opaResultAllow struct {
		Result struct {
			Allow bool `json:"allow"`
		} `json:"result"`
	}

	// Handle simpler OPA responses when OPA URL is of
	// form http://localhost:8181/v1/data/httpapi/authz/allow
	type opaResult struct {

        response = c.get("/items/")
    assert response.status_code == 200
    assert response.json() == snapshot(
        {"session_id": "123", "fatebook_tracker": None, "googall_tracker": None}
    )


def test_openapi_schema(client: TestClient):
    response = client.get("/openapi.json")
    assert response.status_code == 200, response.text
    assert response.json() == snapshot(
        {

     *
     * @param <T> the response type
     * @param request the request being processed
     * @param response the intermediate response
     * @return true if more responses are expected, false otherwise
     */
    protected <T extends Response> boolean handleIntermediate(final Request request, final T response) {
        return false;
    }

    /**

    assert response.status_code == 400, response.text
    assert response.json() == {"detail": "X-Key header invalid"}


def test_get_valid_headers(client: TestClient):
    response = client.get(
        "/items/",
        headers={
            "X-Token": "fake-super-secret-token",
            "X-Key": "fake-super-secret-key",
        },
    )
    assert response.status_code == 200, response.text

    response = client.post("/items/", json={"name": "Foo", "price": 42})
    assert response.status_code == 200, response.text
    assert response.json() == {
        "name": "Foo",
        "price": 42,
        "description": None,
        "tax": None,
        "tags": [],
    }


def test_openapi_schema(client: TestClient):
    response = client.get("/openapi.json")

def test_create_message():
    response = client.post("/messages", params={"input_message": "Hello"})
    assert response.status_code == 200, response.text
    assert response.json() == {
        "input": "Hello",
        "output": {"body": "Processed: Hello", "events": []},
    }


def test_openapi_schema():
    response = client.get("/openapi.json")
    assert response.status_code == 200, response.text

        )

    client = TestClient(app)
    return client


def test_get(client: TestClient):
    response = client.get("/facilities/42")
    assert response.status_code == 200, response.text
    assert response.json() == {
        "id": "42",
        "address": {
            "line_1": "123 Main St",
            "city": "Anytown",
            "state_province": "CA",