Wraps Flagsmith server-side SDK testing patterns (feature flags / feature toggles) so tests run without calling the Flagsmith API: offline mode with LocalFileHandler + a downloaded environment.json snapshot, local-evaluation mode (no per-request network), and default_flag_handler for per-feature mocked fallbacks, via the get_environment_flags / get_identity_flags evaluation paths. Use when writing feature-flag tests for code that uses Flagsmith, mocking flag values, or testing feature toggles offline in CI.