"title": "HTTPValidationError",
                        "type": "object",
                        "properties": {
                            "detail": {
                                "title": "Detail",
                                "type": "array",
                                "items": {
                                    "$ref": "#/components/schemas/ValidationError"

def test_model_optional_str_missing():
    client = TestClient(app)
    response = client.post("/model-optional-str")
    assert response.status_code == 422, response.text
    assert response.json() == {
        "detail": [
            {
                "input": None,
                "loc": ["body"],
                "msg": "Field required",
                "type": "missing",
            },
        ],
    }

        raise InternalError(
            f"The portal gun is too dangerous to be owned by {username}"
        )
    if item_id != "plumbus":
        raise HTTPException(
            status_code=404, detail="Item not found, there's only a plumbus here"
        )

                        "title": "HTTPValidationError",
                        "type": "object",
                        "properties": {
                            "detail": {
                                "title": "Detail",
                                "type": "array",
                                "items": {
                                    "$ref": "#/components/schemas/ValidationError"

                "HTTPValidationError": {
                    "title": "HTTPValidationError",
                    "type": "object",
                    "properties": {
                        "detail": {
                            "title": "Detail",
                            "type": "array",
                            "items": {"$ref": "#/components/schemas/ValidationError"},
                        }
                    },

}

```

但如果客户端请求 `http://example.com/items/bar`（`item_id` `「bar」` 不存在时），则会接收到 HTTP 状态码 - 404（「未找到」错误）及如下 JSON 响应结果：

```JSON
{
  "detail": "Item not found"
}

```

/// tip | 提示

触发 `HTTPException` 时，可以用参数 `detail` 传递任何能转换为 JSON 的值，不仅限于 `str`。

还支持传递 `dict`、`list` 等数据结构。

**FastAPI** 能自动处理这些数据，并将之转换为 JSON。

///

## 添加自定义响应头

有些场景下要为 HTTP 错误添加自定义响应头。例如，出于某些方面的安全需要。

    client = TestClient(mod.app)
    return client


@pytest.mark.parametrize(
    "path,expected_status,expected_response",
    [
        ("/", 200, {"message": "Hello World"}),
        ("/nonexistent", 404, {"detail": "Not Found"}),
    ],
)
def test_get_path(client: TestClient, path, expected_status, expected_response):
    response = client.get(path)
    assert response.status_code == expected_status

                        "properties": {
                            "detail": {
                                "items": {
                                    "$ref": "#/components/schemas/ValidationError"
                                },
                                "type": "array",
                                "title": "Detail",
                            }
                        },

                "HTTPValidationError": {
                    "title": "HTTPValidationError",
                    "type": "object",
                    "properties": {
                        "detail": {
                            "title": "Detail",
                            "type": "array",
                            "items": {"$ref": "#/components/schemas/ValidationError"},
                        }
                    },

                "HTTPValidationError": {
                    "title": "HTTPValidationError",
                    "type": "object",
                    "properties": {
                        "detail": {
                            "title": "Detail",
                            "type": "array",
                            "items": {"$ref": "#/components/schemas/ValidationError"},
                        }
                    },