# 🔬 *️⃣

👆 💪 ⚙️ 🎏 `TestClient` 💯*️⃣.

👉, 👆 ⚙️ `TestClient` `with` 📄, 🔗*️⃣:

```Python hl_lines="27-31"
{!../../../docs_src/app_testing/tutorial002.py!}
```

!!! note

# Testing Dependencies with Overrides

## Overriding dependencies during testing

There are some scenarios where you might want to override a dependency during testing.

You don't want the original dependency to run (nor any of the sub-dependencies it might have).

```

## 覆盖依赖项

接下来，创建覆盖依赖项，并为应用添加覆盖内容。

```Python hl_lines="19-24  27"
{!../../../docs_src/sql_databases/sql_app/tests/test_sql_app.py!}
```

!!! tip "提示"

    `overrider_get_db()` 与 `get_db` 的代码几乎完全一样，只是 `overrider_get_db` 中使用测试数据库的 `TestingSessionLocal`。

## 测试应用

然后，就可以正常测试了。

```Python hl_lines="32-47"
{!../../../docs_src/sql_databases/sql_app/tests/test_sql_app.py!}

You could want to set up a different database for testing, rollback the data after the tests, pre-fill it with some testing data, etc.

The main idea is exactly the same you saw in that previous chapter.

## Add tests for the SQL app

# 测试事件：启动 - 关闭

使用 `TestClient` 和 `with` 语句，在测试中运行事件处理器（`startup` 与 `shutdown`）。

```Python hl_lines="9-12  20-24"
{!../../../docs_src/app_testing/tutorial003.py!}

 * JUnit constructs the instances.
 *
 * <p>This class is emulated in GWT.
 *
 * @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(emulated = true)
@ElementTypesAreNonnullByDefault

 * limitations under the License.
 */

package com.google.common.collect.testing.testers;

import com.google.common.annotations.GwtCompatible;
import com.google.common.collect.testing.AbstractCollectionTester;
import com.google.common.collect.testing.Helpers;
import java.util.Collection;
import java.util.List;
import org.checkerframework.checker.nullness.qual.Nullable;

✋️ 🎂 🎉 📟 🌅 ⚖️ 🌘 🎏, 👥 📁 ⚫️.

```Python hl_lines="8-13"
{!../../../docs_src/sql_databases/sql_app/tests/test_sql_app.py!}
```

!!! tip
    👆 💪 📉 ❎ 👈 📟 🚮 ⚫️ 🔢 & ⚙️ ⚫️ ⚪️➡️ 👯‍♂️ `database.py` & `tests/test_sql_app.py`.

    🦁 & 🎯 🔛 🎯 🔬 📟, 👥 🖨 ⚫️.

## ✍ 💽

↩️ 🔜 👥 🔜 ⚙️ 🆕 💽 🆕 📁, 👥 💪 ⚒ 💭 👥 ✍ 💽 ⏮️:

```Python
Base.metadata.create_all(bind=engine)
```

🔐 🔗 🔬, 👆 🚮 🔑 ⏮️ 🔗 (🔢), & 💲, 👆 🔗 🔐 (➕1️⃣ 🔢).

& ⤴️ **FastAPI** 🔜 🤙 👈 🔐 ↩️ ⏮️ 🔗.

```Python hl_lines="28-29  32"
{!../../../docs_src/dependency_testing/tutorial001.py!}
```

!!! tip
    👆 💪 ⚒ 🔗 🔐 🔗 ⚙️ 🙆 👆 **FastAPI** 🈸.

    ⏮️ 🔗 💪 ⚙️ *➡ 🛠️ 🔢*, *➡ 🛠️ 👨‍🎨* (🕐❔ 👆 🚫 ⚙️ 📨 💲), `.include_router()` 🤙, ♒️.

    FastAPI 🔜 💪 🔐 ⚫️.

对于这些用例，**FastAPI** 应用支持 `app.dependcy_overrides` 属性，该属性就是**字典**。

要在测试时覆盖原有依赖项，这个字典的键应当是原依赖项（函数），值是覆盖依赖项（另一个函数）。

这样一来，**FastAPI** 就会调用覆盖依赖项，不再调用原依赖项。

```Python hl_lines="26-27  30"
{!../../../docs_src/dependency_testing/tutorial001.py!}
```

!!! tip "提示"

    **FastAPI** 应用中的任何位置都可以实现覆盖依赖项。

    原依赖项可用于*路径操作函数*、*路径操作装饰器*（不需要返回值时）、`.include_router()` 调用等。

    FastAPI 可以覆盖这些位置的依赖项。