tests: add a fixture for default_connection to avoid leakage across tests

Author: paultiq

tests/conftest.py

@@ -267,10 +267,18 @@ def spark():
 
 
 @pytest.fixture(scope='function')
-def duckdb_cursor():
-    connection = duckdb.connect('')
-    yield connection
-    connection.close()
+def duckdb_cursor(tmp_path):
+    with duckdb.connect(tmp_path / "mytest") as connection:
+        yield connection
+
+
+@pytest.fixture(scope='function')
+def default_con():
+    # ensures each test uses a fresh default connection to avoid test leakage
+    # threading_unsafe fixture
+    duckdb.default_connection().close()
+    with duckdb.default_connection() as conn:
+        yield conn
 
 
 @pytest.fixture(scope='function')