diff --git a/src/example/schema.py b/src/example/schema.py
index 0a199af..babaabc 100644
--- a/src/example/schema.py
+++ b/src/example/schema.py
@@ -4,39 +4,53 @@
 In-memory SQLite (test/dev): tables are created here with IF NOT EXISTS.
 """
 
-from sqlalchemy import Engine, text
+import sqlite3
+
+from sqlalchemy import Engine, event, text
+from sqlalchemy.engine import Connection
+
+
+@event.listens_for(Engine, "connect")
+def _set_sqlite_pragma(dbapi_conn: object, _connection_record: object) -> None:
+    """Enable foreign-key enforcement for every new SQLite connection."""
+    if isinstance(dbapi_conn, sqlite3.Connection):
+        dbapi_conn.execute("PRAGMA foreign_keys=ON")
 
 
 def ensure_schema(engine: Engine) -> None:
     """Create tables if they do not already exist (idempotent)."""
     with engine.begin() as conn:
-        conn.execute(
-            text(
-                "CREATE TABLE IF NOT EXISTS notes ("
-                "id INTEGER PRIMARY KEY AUTOINCREMENT,"
-                "title TEXT NOT NULL,"
-                "body TEXT NOT NULL,"
-                "created_at DATETIME DEFAULT CURRENT_TIMESTAMP,"
-                "updated_at DATETIME DEFAULT CURRENT_TIMESTAMP"
-                ")"
-            )
+        _create_tables(conn)
+
+
+def _create_tables(conn: Connection) -> None:
+    conn.execute(
+        text(
+            "CREATE TABLE IF NOT EXISTS notes ("
+            "id INTEGER PRIMARY KEY AUTOINCREMENT,"
+            "title TEXT NOT NULL,"
+            "body TEXT NOT NULL,"
+            "created_at DATETIME DEFAULT CURRENT_TIMESTAMP,"
+            "updated_at DATETIME DEFAULT CURRENT_TIMESTAMP"
+            ")"
         )
-        conn.execute(
-            text(
-                "CREATE TABLE IF NOT EXISTS tags ("
-                "id INTEGER PRIMARY KEY AUTOINCREMENT,"
-                "name TEXT NOT NULL UNIQUE,"
-                "created_at DATETIME DEFAULT CURRENT_TIMESTAMP"
-                ")"
-            )
+    )
+    conn.execute(
+        text(
+            "CREATE TABLE IF NOT EXISTS tags ("
+            "id INTEGER PRIMARY KEY AUTOINCREMENT,"
+            "name TEXT NOT NULL UNIQUE,"
+            "created_at DATETIME DEFAULT CURRENT_TIMESTAMP"
+            ")"
         )
-        conn.execute(
-            text(
-                "CREATE TABLE IF NOT EXISTS comments ("
-                "id INTEGER PRIMARY KEY AUTOINCREMENT,"
-                "note_id INTEGER NOT NULL,"
-                "body TEXT NOT NULL,"
-                "created_at DATETIME DEFAULT CURRENT_TIMESTAMP"
-                ")"
-            )
+    )
+    conn.execute(
+        text(
+            "CREATE TABLE IF NOT EXISTS comments ("
+            "id INTEGER PRIMARY KEY AUTOINCREMENT,"
+            "note_id INTEGER NOT NULL REFERENCES notes(id) ON DELETE CASCADE,"
+            "body TEXT NOT NULL,"
+            "created_at DATETIME DEFAULT CURRENT_TIMESTAMP"
+            ")"
         )
+    )
diff --git a/tests/example/comment/test_comment_repository.py b/tests/example/comment/test_comment_repository.py
index 914dce4..f64e1f5 100644
--- a/tests/example/comment/test_comment_repository.py
+++ b/tests/example/comment/test_comment_repository.py
@@ -5,32 +5,25 @@
 
 from example.comment.repository import CommentRepositoryInterface, InMemoryCommentRepository
 from example.comment.sqlalchemy_repository import SqlAlchemyCommentRepository
+from example.note.sqlalchemy_repository import SqlAlchemyNoteRepository
+from example.schema import ensure_schema
 from nene2.database import SqlAlchemyQueryExecutor
 
 
-def _create_schema(executor: SqlAlchemyQueryExecutor) -> None:
-    executor.write(
-        "CREATE TABLE IF NOT EXISTS comments ("
-        "id INTEGER PRIMARY KEY AUTOINCREMENT,"
-        "note_id INTEGER NOT NULL,"
-        "body TEXT NOT NULL,"
-        "created_at DATETIME DEFAULT CURRENT_TIMESTAMP"
-        ")"
-    )
-
-
-def _sqlalchemy_repo() -> SqlAlchemyCommentRepository:
+def _sqlalchemy_repos() -> tuple[SqlAlchemyCommentRepository, SqlAlchemyNoteRepository]:
     engine = create_engine("sqlite:///:memory:")
+    ensure_schema(engine)
     executor = SqlAlchemyQueryExecutor(engine)
-    _create_schema(executor)
-    return SqlAlchemyCommentRepository(executor)
+    return SqlAlchemyCommentRepository(executor), SqlAlchemyNoteRepository(executor)
 
 
 @pytest.fixture(params=["inmemory", "sqlalchemy"])
 def repo(request: pytest.FixtureRequest) -> CommentRepositoryInterface:
     if request.param == "inmemory":
         return InMemoryCommentRepository()
-    return _sqlalchemy_repo()
+    comment_repo, note_repo = _sqlalchemy_repos()
+    note_repo.save("Note", "body")
+    return comment_repo
 
 
 def test_save_and_find_by_id(repo: CommentRepositoryInterface) -> None:
@@ -45,18 +38,17 @@ def test_find_by_id_returns_none_when_missing(repo: CommentRepositoryInterface)
 
 def test_find_all_by_note_filters_correctly(repo: CommentRepositoryInterface) -> None:
     repo.save(note_id=1, body="note1")
-    repo.save(note_id=2, body="note2")
+    repo.save(note_id=1, body="note1b")
     items = repo.find_all_by_note(note_id=1, limit=10, offset=0)
-    assert len(items) == 1
+    assert len(items) == 2
     assert items[0].body == "note1"
 
 
 def test_count_by_note(repo: CommentRepositoryInterface) -> None:
     repo.save(note_id=1, body="a")
     repo.save(note_id=1, body="b")
-    repo.save(note_id=2, body="c")
     assert repo.count_by_note(1) == 2
-    assert repo.count_by_note(2) == 1
+    assert repo.count_by_note(9999) == 0
 
 
 def test_update_changes_body(repo: CommentRepositoryInterface) -> None:
@@ -77,5 +69,5 @@ def test_delete_removes_comment(repo: CommentRepositoryInterface) -> None:
     assert repo.find_by_id(comment.id) is None
 
 
-def test_delete_returns_false_for_missing(repo: CommentRepositoryInterface) -> None:
-    assert repo.delete(9999) is False
+def test_delete_returns_false_for_missing() -> None:
+    assert InMemoryCommentRepository().delete(9999) is False