PrintWriter w = new PrintWriter(Files.newWriter(temp, UTF_8));
    w.println("hello");
    w.println("");
    w.println(" world  ");
    w.println("");
    w.close();

    assertEquals("hello", Files.readFirstLine(temp, UTF_8));
    assertEquals(ImmutableList.of("hello", "", " world  ", ""), Files.readLines(temp, UTF_8));

    assertTrue(temp.delete());
  }

In this case, the original path `/app` would actually be served at `/api/v1/app`.

Even though all your code is written assuming there's just `/app`.

{* ../../docs_src/behind_a_proxy/tutorial001_py39.py hl[6] *}

     * @return the class realm of core.
     */
    @Nonnull
    ClassRealm getRealm();

    /**
     * Shorthand method to obtain the {@link ClassWorld} used for Maven Core.
     *
     * @return the class world in use.
     */
    @Nonnull
    default ClassWorld getClassWorld() {
        return getRealm().getWorld();
    }

from docs_src.behind_a_proxy.tutorial003_py39 import app

client = TestClient(app)


def test_main():
    response = client.get("/app")
    assert response.status_code == 200
    assert response.json() == {"message": "Hello World", "root_path": "/api/v1"}


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

<span style="color: green;">INFO</span>:     Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit)
```

</div>

返回的响应如下：

```JSON
{
    "message": "Hello World",
    "root_path": "/api/v1"
}
```

### 在 FastAPI 应用里设置 `root_path`

还有一种方案，如果不能提供 `--root-path` 或等效的命令行选项，则在创建 FastAPI 应用时要设置 `root_path` 参数。

{* ../../docs_src/behind_a_proxy/tutorial002.py hl[3] *}

    uvicorn_run_mock.assert_not_called()


def test_get_root(client: TestClient):
    response = client.get("/")
    assert response.status_code == 200
    assert response.json() == {"hello world": "ba"}


def test_uvicorn_run_called_when_run_as_main():  # Just for coverage
    if sys.modules.get(MOD_NAME):
        del sys.modules[MOD_NAME]
    with unittest.mock.patch("uvicorn.run") as uvicorn_run_mock:

    assertThat(headersToList(response)).containsExactly("Cookie: a=android")
  }

  @Test
  fun regularResponse() {
    server.enqueue(MockResponse().setBody("hello world"))
    val url = server.url("/").toUrl()
    val connection = url.openConnection() as HttpURLConnection
    connection.setRequestProperty("Accept-Language", "en-US")
    val inputStream = connection.inputStream

    }

    @Test
    public void testGetContentAsStringWithCache() throws IOException {
        CurlResponse response = new CurlResponse();
        response.setEncoding("UTF-8");
        String testContent = "Hello, World!";
        byte[] data = testContent.getBytes("UTF-8");
        ContentCache cache = new ContentCache(data);
        response.setContentCache(cache);

        String content = response.getContentAsString();

		CreatedTime:     createdAt.Unix(),
		UpdatedTime:     &updatedAt,
		JobInfo: Job{
			Title:    "programmer",
			Number:   9920,
			Location: "Kenmawr",
			IsIntern: false,
		},
		CustomSerializerString: "world",
	}

	if err := DB.Create(&data).Error; err != nil {
		t.Fatalf("failed to create data, got error %v", err)
	}

	var result SerializerStruct

    assert response.status_code == 404, response.text


def test_root():
    client = get_client()
    response = client.get("/")
    assert response.status_code == 200
    assert response.json() == {"message": "Hello World"}


def test_default_openapi():
    client = get_client()
    response = client.get("/docs")
    assert response.status_code == 200, response.text
    response = client.get("/redoc")