add integration tests for admin, auth, user management, and database initialization

backend/tests/test_db.py

@@ -0,0 +1,54 @@
+"""Tests for DuckDB initialization and schema."""
+import pytest
+import duckdb
+
+from backend.app import db as db_module
+
+
+@pytest.fixture(autouse=True)
+def fresh_db():
+    """Use an in-memory DB for each test and reset global state."""
+    db_module._conn = None
+    yield
+    db_module.close_db()
+    db_module._conn = None
+
+
+def test_init_creates_users_table():
+    conn = db_module.init_db(":memory:")
+    result = conn.execute(
+        "SELECT table_name FROM information_schema.tables WHERE table_name = 'users'"
+    ).fetchone()
+    assert result is not None
+
+
+def test_init_creates_refresh_tokens_table():
+    conn = db_module.init_db(":memory:")
+    result = conn.execute(
+        "SELECT table_name FROM information_schema.tables WHERE table_name = 'refresh_tokens'"
+    ).fetchone()
+    assert result is not None
+
+
+def test_init_is_idempotent():
+    conn1 = db_module.init_db(":memory:")
+    conn2 = db_module.init_db(":memory:")
+    assert conn1 is conn2
+
+
+def test_get_conn_raises_before_init():
+    with pytest.raises(RuntimeError, match="not initialised"):
+        db_module.get_conn()
+
+
+def test_get_conn_returns_connection_after_init():
+    db_module.init_db(":memory:")
+    conn = db_module.get_conn()
+    assert conn is not None
+
+
+def test_close_db_resets_connection():
+    db_module.init_db(":memory:")
+    db_module.close_db()
+    with pytest.raises(RuntimeError):
+        db_module.get_conn()