assert response.json() == openapi_schema_main


def test_main():
    response = client.get("/app")
    assert response.status_code == 200, response.text
    assert response.json() == {"message": "Hello World from main app"}


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

예를 들어 다음과 같은 `main.py` 파일이 있다고 합시다:

```Python hl_lines="3"
import os

name = os.getenv("MY_NAME", "World")
print(f"Hello {name} from Python")
```

/// tip | 팁

<a href="https://docs.python.org/3.8/library/os.html#os.getenv" class="external-link" target="_blank">`os.getenv()`</a> 의 두 번째 인자는 반환할 기본값입니다.

여기서는 `"World"`를 넣었기에 기본값으로써 사용됩니다. 넣지 않으면 `None` 이 기본값으로 사용됩니다.

///

그러면 해당 파이썬 프로그램을 다음과 같이 호출할 수 있습니다:

client = TestClient(app)


def test_path_operation():
    response = client.get("/headers/")
    assert response.status_code == 200, response.text
    assert response.json() == {"message": "Hello World"}
    assert response.headers["X-Cat-Dog"] == "alone in the world"

```txt
Hello, World from Flask!
```

And if you go to <a href="http://localhost:8000/v2" class="external-link" target="_blank">http://localhost:8000/v2</a> you will see the response from FastAPI:

```JSON
{
    "message": "Hello World"
}

    assertEquals("Hello, World!", builder.toString());
  }

  public void testAppendMethods() throws IOException {
    StringBuilder builder = new StringBuilder();
    Writer writer = new AppendableWriter(builder);

    writer.append("Hello,");
    writer.append(' ');
    writer.append("The World Wide Web", 4, 9);
    writer.append("!");

    assertEquals("Hello, World!", builder.toString());
  }

```txt
Hello, World from Flask!
```

А если вы перейдёте по <a href="http://localhost:8000/v2" class="external-link" target="_blank">http://localhost:8000/v2</a>, вы увидите HTTP‑ответ от FastAPI:

```JSON
{
    "message": "Hello World"
}

from fastapi import FastAPI
from fastapi.testclient import TestClient
from fastapi.websockets import WebSocket

app = FastAPI()


@app.get("/")
async def read_main():
    return {"msg": "Hello World"}


@app.websocket("/ws")
async def websocket(websocket: WebSocket):
    await websocket.accept()
    await websocket.send_json({"msg": "Hello WebSocket"})
    await websocket.close()


def test_read_main():

@app.api_route("/api_route")
def non_operation():
    return {"message": "Hello World"}


def non_decorated_route():
    return {"message": "Hello World"}


app.add_api_route("/non_decorated_route", non_decorated_route)


@app.get("/text")
def get_text():
    return "Hello World"


@app.get("/path/{item_id}")
def get_id(item_id):
    return item_id

```txt
Hello, World from Flask!
```

并且如果您访问 <a href="http://localhost:8000/v2" class="external-link" target="_blank">http://localhost:8000/v2</a>，您将会看到由 FastAPI 返回的响应：

```JSON
{
    "message": "Hello World"
}

```txt
Hello, World from Flask!
```

E se você for até <a href="http://localhost:8000/v2" class="external-link" target="_blank">http://localhost:8000/v2</a>, você verá o retorno do FastAPI:

```JSON
{
    "message": "Hello World"
}