feat(backend): add cyclone.db with engine, SessionLocal, Base, init_db

backend/tests/test_db.py

@@ -0,0 +1,41 @@
+"""Tests for the SQLAlchemy engine + session factory + init_db."""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+import pytest
+import sqlalchemy as sa
+
+from cyclone import db
+
+
+@pytest.fixture(autouse=True)
+def _isolated_db(tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> None:
+    """Point CYCLONE_DB_URL at a temp file for every test in this module."""
+    url = f"sqlite:///{tmp_path}/test.db"
+    monkeypatch.setenv("CYCLONE_DB_URL", url)
+    # Reset module-level state so each test gets a fresh engine.
+    db._reset_for_tests()
+
+
+def test_init_db_creates_engine() -> None:
+    db.init_db()
+    assert db.engine() is not None
+    assert isinstance(db.engine(), sa.Engine)
+
+
+def test_init_db_creates_all_tables() -> None:
+    db.init_db()
+    # Probe known future table names from the schema. We use
+    # `inspect` rather than importing the model class to keep this
+    # test independent of model implementation.
+    inspector = sa.inspect(db.engine())
+    # In Task 3 we add a Claim table; until then this is empty.
+    assert isinstance(inspector.get_table_names(), list)
+
+
+def test_session_local_returns_session() -> None:
+    db.init_db()
+    with db.SessionLocal()() as s:
+        assert s.is_active