Tests must properly clean up resources and avoid side effects that can impact other tests, especially when running in parallel. This prevents non-deterministic failures and ensures reliable test execution. Key practices: - Clean up any created resources (tables, files, connections) after test completion - Use unique identifiers for test resources to avoid conflicts - Ensure tests don't leave persistent state that affects subsequent tests - Consider using test fixtures or teardown methods for consistent cleanup Example of proper cleanup: ```python def test_streaming_foreach_batch_external_column(self): table_name = "testTable_foreach_batch_external_column" try: # Test logic here pass finally: # Clean up the table to avoid affecting other tests self.spark.sql(f"DROP TABLE IF EXISTS {table_name}") ``` This approach prevents issues where tests affect catalog-related tests or cause hanging/flaky behavior when run in parallel environments.