test: add repository factory and CLI db-reset tests

- test_factory.py: verify database factory selects correct backend
- test_cli_db_reset.py: test CLI database reset functionality

tests/test_factory.py

@@ -0,0 +1,44 @@
+"""
+Unit tests for the repository factory — dispatch on DECNET_DB_TYPE.
+"""
+import pytest
+
+from decnet.web.db.factory import get_repository
+from decnet.web.db.sqlite.repository import SQLiteRepository
+from decnet.web.db.mysql.repository import MySQLRepository
+
+
+def test_factory_defaults_to_sqlite(monkeypatch, tmp_path):
+    monkeypatch.delenv("DECNET_DB_TYPE", raising=False)
+    repo = get_repository(db_path=str(tmp_path / "t.db"))
+    assert isinstance(repo, SQLiteRepository)
+
+
+def test_factory_sqlite_explicit(monkeypatch, tmp_path):
+    monkeypatch.setenv("DECNET_DB_TYPE", "sqlite")
+    repo = get_repository(db_path=str(tmp_path / "t.db"))
+    assert isinstance(repo, SQLiteRepository)
+
+
+def test_factory_mysql_branch(monkeypatch):
+    """MySQL branch must import and instantiate without a live server.
+
+    Engine creation is lazy in SQLAlchemy — no socket is opened until the
+    first query — so the repository constructs cleanly here.
+    """
+    monkeypatch.setenv("DECNET_DB_TYPE", "mysql")
+    monkeypatch.setenv("DECNET_DB_URL", "mysql+aiomysql://u:p@127.0.0.1:3306/x")
+    repo = get_repository()
+    assert isinstance(repo, MySQLRepository)
+
+
+def test_factory_is_case_insensitive(monkeypatch, tmp_path):
+    monkeypatch.setenv("DECNET_DB_TYPE", "SQLite")
+    repo = get_repository(db_path=str(tmp_path / "t.db"))
+    assert isinstance(repo, SQLiteRepository)
+
+
+def test_factory_rejects_unknown_type(monkeypatch):
+    monkeypatch.setenv("DECNET_DB_TYPE", "cassandra")
+    with pytest.raises(ValueError, match="Unsupported database type"):
+        get_repository()