Running tests via pytest throws RuntimeError: Event loop is closed

[FumaxIN]

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Example Code

client = TestClient(app)


def test_login():
    response = client.post(
        "/login",
        data={
            "username": "testuser1",
            "password": "qwerty@123"
        }
    )
    assert response.status_code == 200
    assert response.json()["access_token"]


def test_login_b():
    response = client.post(
        "/login",
        data={
            "username": "johndoe",
            "password": "qwerty@123"
        }
    )
    assert response.status_code == 200
    assert response.json()["access_token"]


### LOGIN ###

@app.post("/login", tags=["auth"])
async def login(request: OAuth2PasswordRequestForm = Depends()):
    user = await db["users"].find_one({"username": request.username})
    if not user:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail=f"Invalid username or password"
        )
    if not Hash.verify(user["password"], request.password):
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail=f"Invalid username or password"
        )
    access_token = create_access_token(data={"sub": user["username"]})
    return {"access_token": access_token, "token_type": "bearer"}

Description

I am working on a blog management project using MongoDB Atlas as my database.

All the routes are working fine but I am facing issues with Tests.
The first test always works fine but the second and other subsequent tests fail with an error RuntimeError: Event loop is closed

Please help me understand and fix this.

Operating System

Linux

Operating System Details

No response

FastAPI Version

0.111.0

Pydantic Version

2.7.1

Python Version

3.12.3

Additional Context

No response

[YuriiMotov]

I guess you are using pytest-asyncio library.
If so, it's a known issue of pytest-asyncio (pytest-dev/pytest-asyncio#706). It's recommended to use version 0.21.2 or less of pytest-asyncio to avoid this problem

[FumaxIN]

This StackOverflow answer did the job