## Parameterize the instance { #parameterize-the-instance }

And now, we can use `__init__` to declare the parameters of the instance that we can use to "parameterize" the dependency:

{* ../../docs_src/dependencies/tutorial011_an_py310.py hl[9] *}

    // "latest" here is intentional, since the image name specifies "8"
    UBI("docker.elastic.co/ubi8/ubi-minimal:latest", "-ubi8"),

    // The Iron Bank base image is UBI (albeit hardened), but we are required to parameterize the Docker build
    IRON_BANK("${BASE_REGISTRY}/${BASE_IMAGE}:${BASE_TAG}", "-ironbank"),

    // Base image with extras for Cloud
    CLOUD("centos:8", "-cloud"),

 *
 * @param <G> the type of the test generator required by this tester. An instance of G should
 *     somehow provide an instance of the class under test, plus any other information required to
 *     parameterize the test.
 * @author George van den Driessche
 */
@GwtCompatible
@NullMarked
public class AbstractTester<G> extends TestCase {
  private G subjectGenerator;
  private String suiteName;

 *
 * @param <G> the type of the test generator required by this tester. An instance of G should
 *     somehow provide an instance of the class under test, plus any other information required to
 *     parameterize the test.
 * @author George van den Driessche
 */
@GwtCompatible
@NullMarked
public class AbstractTester<G> extends TestCase {
  private G subjectGenerator;
  private String suiteName;

 * @param <G> The type of the generator to be passed to testers in the generated test suite. An
 *     instance of G should somehow provide an instance of the class under test, plus any other
 *     information required to parameterize the test.
 * @see FeatureSpecificTestSuiteBuilder
 * @author George van den Driessche
 */
@GwtIncompatible
public abstract class PerCollectionSizeTestSuiteBuilder<

 * @param <G> The type of the generator to be passed to testers in the generated test suite. An
 *     instance of G should somehow provide an instance of the class under test, plus any other
 *     information required to parameterize the test.
 * @see FeatureSpecificTestSuiteBuilder
 * @author George van den Driessche
 */
@GwtIncompatible
public abstract class PerCollectionSizeTestSuiteBuilder<

## Parametrizar la instance { #parameterize-the-instance }

Y ahora, podemos usar `__init__` para declarar los parámetros de la instance que podemos usar para "parametrizar" la dependencia:

{* ../../docs_src/dependencies/tutorial011_an_py310.py hl[9] *}

## 参数化实例 { #parameterize-the-instance }

现在，我们可以用 `__init__` 声明实例的参数，用来“参数化”这个依赖项：

{* ../../docs_src/dependencies/tutorial011_an_py310.py hl[9] *}

在本例中，**FastAPI** 不会接触或关心 `__init__`，我们会在自己的代码中直接使用它。

## 创建实例 { #create-an-instance }

我们可以这样创建该类的实例：

{* ../../docs_src/dependencies/tutorial011_an_py310.py hl[18] *}

在這個情境中，**FastAPI** 會用這個 `__call__` 來檢查額外的參數與子相依，並在之後呼叫它，把回傳值傳遞給你的「路徑操作函式」中的參數。

## 讓實例可參數化 { #parameterize-the-instance }

接著，我們可以用 `__init__` 來宣告這個實例的參數，用以「參數化」這個相依：

{* ../../docs_src/dependencies/tutorial011_an_py310.py hl[9] *}

在這裡，**FastAPI** 完全不會接觸或在意 `__init__`，我們會直接在自己的程式碼中使用它。

## 建立一個實例 { #create-an-instance }

我們可以這樣建立該類別的實例：

{* ../../docs_src/dependencies/tutorial011_an_py310.py hl[18] *}

            }
        ]
    )


@pytest.mark.parametrize(
    "path",
    ["/optional-str", "/model-optional-str"],
)
def test_optional_str_missing(path: str):
    client = TestClient(app)
    response = client.get(path)
    assert response.status_code == 200
    assert response.json() == {"p": None}


@pytest.mark.parametrize(
    "path",
    ["/optional-str", "/model-optional-str"],
)