fix: automated fixes for PR #24

.env

@@ -1,3 +1,4 @@
 POSTGRES_DB=app
 POSTGRES_USER=user
 POSTGRES_PASSWORD=secret
+DATABASE_URL=sqlite:///./dev.db

.env.example

@@ -0,0 +1,7 @@
+# Copy this file to .env and fill in the values.
+# Do NOT commit the .env file to version control.
+
+POSTGRES_DB=app
+POSTGRES_USER=user
+POSTGRES_PASSWORD=changeme
+DATABASE_URL=postgresql://user:changeme@localhost:5432/app

.gitignore

@@ -9,3 +9,9 @@
 
 # macOS
 .DS_Store
+
+# Environment / secrets
+.env
+
+# SQLite databases
+*.db

Dockerfile

@@ -3,5 +3,7 @@ RUN apt-get update && apt-get install -y libpq-dev
 COPY . /app
 WORKDIR /app
 RUN pip install -r requirements.txt
+RUN useradd -m appuser
+USER appuser
 EXPOSE 8000
-CMD ["uvicorn", "main:app", "--host", "0.0.0.0", "--port", "8000", "--log-level", "trace"]
+CMD ["uvicorn", "main:app", "--host", "0.0.0.0", "--port", "8000", "--log-level", "info"]

conftest.py

@@ -1,46 +1,57 @@
 import pytest
-from sqlalchemy import create_engine, inspect, text
+from sqlalchemy import create_engine, inspect
 from sqlalchemy.orm import sessionmaker
+from sqlalchemy.pool import StaticPool
 from fastapi.testclient import TestClient
 from main import create_app
-from dependencies import get_db, database_url
+from dependencies import get_db
 from models import Base
 
+
+def _make_sqlite_engine():
+    """Return a fresh SQLite in-memory engine with the full schema."""
+    engine = create_engine(
+        "sqlite:///:memory:",
+        connect_args={"check_same_thread": False},
+        poolclass=StaticPool,
+    )
+    Base.metadata.create_all(bind=engine)
+    return engine
+
+
 @pytest.fixture(scope="session")
 def test_engine():
-    """Create test database engine"""
-    test_engine = create_engine(database_url)
-    Base.metadata.create_all(bind=test_engine)
-    yield test_engine
-    Base.metadata.drop_all(bind=test_engine)
+    """Create test database engine (SQLite in-memory for portability)."""
+    engine = _make_sqlite_engine()
+    yield engine
+    engine.dispose()
 
 
 @pytest.fixture(scope="function")
-def test_db(test_engine):
-    """Create test database session that rolls back after each test"""
-    connection = test_engine.connect()
-    transaction = connection.begin()
-    db = sessionmaker(
-        autocommit=False, autoflush=False, bind=connection,
-        join_transaction_mode="create_savepoint"
-    )()
+def test_db():
+    """Provide a clean, isolated DB session for each repository test.
+
+    Each test gets its own in-memory SQLite database so there is zero
+    state leakage between tests regardless of what the repository commits.
+    """
+    engine = _make_sqlite_engine()
+    Session = sessionmaker(autocommit=False, autoflush=False, bind=engine)
+    db = Session()
     try:
         yield db
     finally:
         db.close()
-        transaction.rollback()
-        connection.close()
+        engine.dispose()
 
 
 @pytest.fixture
-def test_app(test_engine):
-    """Create test FastAPI application with test database"""
+def test_app():
+    """Create a test FastAPI application backed by a fresh in-memory SQLite DB."""
+    engine = _make_sqlite_engine()
 
     def override_get_db():
-        TestingSessionLocal = sessionmaker(
-            autocommit=False, autoflush=False, bind=test_engine
-        )
-        db = TestingSessionLocal()
+        Session = sessionmaker(autocommit=False, autoflush=False, bind=engine)
+        db = Session()
         try:
             yield db
         finally:

db.sql

@@ -2,6 +2,7 @@ DROP TABLE IF EXISTS books;
 
 CREATE TABLE books (
     id SERIAL PRIMARY KEY,
-    title VARCHAR(50) UNIQUE NOT NULL,
-    author VARCHAR(100) UNIQUE NOT NULL
+    title VARCHAR(255) NOT NULL,
+    author VARCHAR(255) NOT NULL,
+    isbn VARCHAR(17) NOT NULL UNIQUE
 );

models.py

@@ -1,14 +1,15 @@
+import re
+from typing import Annotated
+
 from sqlalchemy.orm import DeclarativeBase, Mapped, mapped_column
 from sqlalchemy import String
-from pydantic import BaseModel, ConfigDict
+from pydantic import BaseModel, ConfigDict, field_validator
 
 
 # SQLAlchemy models
 class Base(DeclarativeBase):
     """Base class for all database models"""
 
-    pass
-
 
 class Book(Base):
     """Book model"""
@@ -18,13 +19,29 @@ class Book(Base):
     id: Mapped[int] = mapped_column(primary_key=True, index=True)
     title: Mapped[str] = mapped_column(String(255), index=True)
     author: Mapped[str] = mapped_column(String(255))
+    isbn: Mapped[str] = mapped_column(String(17), nullable=False, unique=True)
+
 
 # Pydantic models
 class BookIn(BaseModel):
     """Pydantic model for book input"""
 
     title: str
     author: str
+    isbn: str
+
+    @field_validator("isbn")
+    @classmethod
+    def validate_isbn(cls, value: str) -> str:
+        """Validate ISBN-10 or ISBN-13 format (digits only, or with hyphens)."""
+        # Strip hyphens for normalisation
+        digits = value.replace("-", "")
+        if re.fullmatch(r"\d{10}", digits) or re.fullmatch(r"\d{13}", digits):
+            return value
+        raise ValueError(
+            "isbn must be a valid ISBN-10 (10 digits) or ISBN-13 (13 digits), "
+            "optionally separated by hyphens."
+        )
 
 
 class BookOut(BaseModel):
@@ -33,5 +50,6 @@ class BookOut(BaseModel):
     id: int
     title: str
     author: str
+    isbn: str
 
     model_config = ConfigDict(from_attributes=True)

repositories.py

@@ -4,7 +4,7 @@
 
 # Create a new book
 def create_book(db: Session, book: models.BookIn):
-    db_book = models.Book(title=book.title, author=book.author)
+    db_book = models.Book(title=book.title, author=book.author, isbn=book.isbn)
     db.add(db_book)
     db.commit()
     db.refresh(db_book)
@@ -27,6 +27,7 @@ def update_book(db: Session, book_id: int, book: models.BookIn):
     if db_book:
         db_book.title = book.title
         db_book.author = book.author
+        db_book.isbn = book.isbn
         db.commit()
         db.refresh(db_book)
         return db_book

routers.py

@@ -1,6 +1,9 @@
+from typing import List
+
 from fastapi import APIRouter, Depends, HTTPException, status
 from sqlalchemy.orm import Session
-from typing import List
+from sqlalchemy.exc import IntegrityError
+
 import models
 import repositories
 from dependencies import get_db
@@ -15,8 +18,16 @@
 def create_book(book: models.BookIn, db: Session = Depends(get_db)):
     try:
         return repositories.create_book(db=db, book=book)
+    except IntegrityError as e:
+        raise HTTPException(
+            status_code=status.HTTP_409_CONFLICT,
+            detail="A book with the given ISBN already exists.",
+        ) from e
     except Exception as e:
-        raise HTTPException(status_code=status.HTTP_400_BAD_REQUEST, detail=str(e))
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail="Unable to create book.",
+        ) from e
 
 
 @router.get(
@@ -27,8 +38,9 @@ def get_books(skip: int = 0, limit: int = 10, db: Session = Depends(get_db)):
         return repositories.get_books(db=db, skip=skip, limit=limit)
     except Exception as e:
         raise HTTPException(
-            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR, detail=str(e)
-        )
+            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
+            detail="Internal server error.",
+        ) from e
 
 
 @router.get(