with some tests

backend/database.py

@@ -0,0 +1,18 @@
+import os
+from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine, async_sessionmaker
+from sqlalchemy.orm import DeclarativeBase
+
+DATABASE_URL = os.getenv("DATABASE_URL", "postgresql+asyncpg://postgres:postgres@localhost:5432/arbret")
+
+engine = create_async_engine(DATABASE_URL)
+async_session = async_sessionmaker(engine, expire_on_commit=False)
+
+
+class Base(DeclarativeBase):
+    pass
+
+
+async def get_db():
+    async with async_session() as session:
+        yield session
+

backend/main.py

@@ -1,7 +1,21 @@
-from fastapi import FastAPI
+from contextlib import asynccontextmanager
+from fastapi import FastAPI, Depends
 from fastapi.middleware.cors import CORSMiddleware
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
 
-app = FastAPI()
+from database import engine, get_db, Base
+from models import Counter
+
+
+@asynccontextmanager
+async def lifespan(app: FastAPI):
+    async with engine.begin() as conn:
+        await conn.run_sync(Base.metadata.create_all)
+    yield
+
+
+app = FastAPI(lifespan=lifespan)
 
 app.add_middleware(
     CORSMiddleware,
@@ -11,7 +25,27 @@ app.add_middleware(
 )
 
 
-@app.get("/api/hello")
-def hello():
-    return {"message": "Hello from FastAPI"}
+async def get_or_create_counter(db: AsyncSession) -> Counter:
+    result = await db.execute(select(Counter).where(Counter.id == 1))
+    counter = result.scalar_one_or_none()
+    if not counter:
+        counter = Counter(id=1, value=0)
+        db.add(counter)
+        await db.commit()
+        await db.refresh(counter)
+    return counter
+
+
+@app.get("/api/counter")
+async def get_counter(db: AsyncSession = Depends(get_db)):
+    counter = await get_or_create_counter(db)
+    return {"value": counter.value}
+
+
+@app.post("/api/counter/increment")
+async def increment_counter(db: AsyncSession = Depends(get_db)):
+    counter = await get_or_create_counter(db)
+    counter.value += 1
+    await db.commit()
+    return {"value": counter.value}
 

backend/models.py

@@ -0,0 +1,11 @@
+from sqlalchemy import Integer
+from sqlalchemy.orm import Mapped, mapped_column
+from database import Base
+
+
+class Counter(Base):
+    __tablename__ = "counter"
+
+    id: Mapped[int] = mapped_column(Integer, primary_key=True, default=1)
+    value: Mapped[int] = mapped_column(Integer, default=0)
+

backend/pyproject.toml

@@ -5,5 +5,15 @@ requires-python = ">=3.11"
 dependencies = [
     "fastapi>=0.115.6",
     "uvicorn>=0.34.0",
+    "sqlalchemy[asyncio]>=2.0.36",
+    "asyncpg>=0.30.0",
+]
+
+[dependency-groups]
+dev = [
+    "pytest>=8.3.4",
+    "pytest-asyncio>=0.25.0",
+    "httpx>=0.28.1",
+    "aiosqlite>=0.20.0",
 ]
 

backend/pytest.ini

@@ -0,0 +1,4 @@
+[pytest]
+asyncio_mode = auto
+asyncio_default_fixture_loop_scope = function
+

backend/tests/test_counter.py

@@ -0,0 +1,60 @@
+import pytest
+from httpx import ASGITransport, AsyncClient
+from sqlalchemy.ext.asyncio import create_async_engine, async_sessionmaker
+
+from database import Base, get_db
+from main import app
+
+TEST_DATABASE_URL = "sqlite+aiosqlite:///:memory:"
+
+
+@pytest.fixture
+async def client():
+    engine = create_async_engine(TEST_DATABASE_URL)
+    async_session = async_sessionmaker(engine, expire_on_commit=False)
+
+    async with engine.begin() as conn:
+        await conn.run_sync(Base.metadata.create_all)
+
+    async def override_get_db():
+        async with async_session() as session:
+            yield session
+
+    app.dependency_overrides[get_db] = override_get_db
+
+    async with AsyncClient(transport=ASGITransport(app=app), base_url="http://test") as c:
+        yield c
+
+    app.dependency_overrides.clear()
+    await engine.dispose()
+
+
+@pytest.mark.asyncio
+async def test_get_counter_initial(client):
+    response = await client.get("/api/counter")
+    assert response.status_code == 200
+    assert response.json() == {"value": 0}
+
+
+@pytest.mark.asyncio
+async def test_increment_counter(client):
+    response = await client.post("/api/counter/increment")
+    assert response.status_code == 200
+    assert response.json() == {"value": 1}
+
+
+@pytest.mark.asyncio
+async def test_increment_counter_multiple(client):
+    await client.post("/api/counter/increment")
+    await client.post("/api/counter/increment")
+    response = await client.post("/api/counter/increment")
+    assert response.json() == {"value": 3}
+
+
+@pytest.mark.asyncio
+async def test_get_counter_after_increment(client):
+    await client.post("/api/counter/increment")
+    await client.post("/api/counter/increment")
+    response = await client.get("/api/counter")
+    assert response.json() == {"value": 2}
+