from fastapi.testclient import TestClient

from docs_src.wsgi.tutorial001_py39 import app

client = TestClient(app)


def test_flask():
    response = client.get("/v1/")
    assert response.status_code == 200, response.text
    assert response.text == "Hello, World from Flask!"


def test_app():
    response = client.get("/v2")
    assert response.status_code == 200, response.text

import pytest
from fastapi.testclient import TestClient

from .app.main import app

client = TestClient(app)


@pytest.mark.parametrize(
    "path", ["/a/compute", "/a/compute/", "/b/compute", "/b/compute/"]
)
def test_post(path):
    data = {"a": 2, "b": "foo"}
    response = client.post(path, json=data)
    assert response.status_code == 200, response.text
    assert data == response.json()


@pytest.mark.parametrize(

### **FastAPI** app file { #fastapi-app-file }

Let's say you have a file structure as described in [Bigger Applications](bigger-applications.md){.internal-link target=_blank}:

```
.
├── app
│   ├── __init__.py
│   └── main.py
```

In the file `main.py` you have your **FastAPI** app:


{* ../../docs_src/app_testing/app_a_py39/main.py *}

from typing import Union

from fastapi import FastAPI, Header
from pydantic import BaseModel

app = FastAPI()


class CommonHeaders(BaseModel):
    host: str
    save_data: bool
    if_modified_since: Union[str, None] = None
    traceparent: Union[str, None] = None
    x_tag: list[str] = []


@app.get("/items/")
async def read_items(headers: CommonHeaders = Header(convert_underscores=False)):

from fastapi import FastAPI
from pydantic import BaseModel


class Item(BaseModel):
    name: str
    description: str | None = None
    price: float
    tax: float | None = None


app = FastAPI()


@app.post("/items/")
async def create_item(item: Item):
    item_dict = item.model_dump()
    if item.tax is not None:
        price_with_tax = item.price + item.tax
        item_dict.update({"price_with_tax": price_with_tax})

from fastapi import FastAPI
from pydantic import BaseModel


class Item(BaseModel):
    name: str
    description: str | None = None
    price: float
    tax: float | None = None


app = FastAPI()


@app.put("/items/{item_id}")
async def update_item(item_id: int, item: Item, q: str | None = None):
    result = {"item_id": item_id, **item.model_dump()}
    if q:
        result.update({"q": q})

from typing import Annotated

from fastapi import Body, FastAPI
from pydantic import BaseModel

app = FastAPI()


class Item(BaseModel):
    name: str
    description: str | None = None
    price: float
    tax: float | None = None


@app.put("/items/{item_id}")
async def update_item(item_id: int, item: Annotated[Item, Body(embed=True)]):
    results = {"item_id": item_id, "item": item}

from typing import Literal

from fastapi import FastAPI, Query
from pydantic import BaseModel, Field

app = FastAPI()


class FilterParams(BaseModel):
    limit: int = Field(100, gt=0, le=100)
    offset: int = Field(0, ge=0)
    order_by: Literal["created_at", "updated_at"] = "created_at"
    tags: list[str] = []


@app.get("/items/")
async def read_items(filter_query: FilterParams = Query()):

from typing import Annotated, Union

from fastapi import FastAPI, Header
from pydantic import BaseModel

app = FastAPI()


class CommonHeaders(BaseModel):
    host: str
    save_data: bool
    if_modified_since: Union[str, None] = None
    traceparent: Union[str, None] = None
    x_tag: list[str] = []


@app.get("/items/")
async def read_items(
    headers: Annotated[CommonHeaders, Header(convert_underscores=False)],
):

So, the section:

```Python
    uvicorn.run(app, host="0.0.0.0", port=8000)
```

will run.

---

This won't happen if you import that module (file).

So, if you have another file `importer.py` with:

```Python
from myapp import app

# Some more code
```