testing-patterns

Testing & Quality

Use when writing or modifying tests under tests/ — base testcase inheritance, pytest markers, fixtures, in-memory vs real-broker testing, and how to run the suite.

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FastStream Testing Patterns

Running tests

Run pytest directly or via just — never through the rtk proxy.

All just test* recipes run inside the dev container (docker compose exec faststream) — start it with just up first.

just test [path] — fast suite: -m "not slow and not connected", parallel -n auto.
just test-kafka / test-rabbit / test-nats / test-redis / test-redis-cluster / test-confluent — per-broker subset excluding connected and slow; the -all variants run every broker-marked test including slow/connected ones (that broker must be up).
just test-all — the full suite (-m "all").
Direct, no container needed: uv run pytest tests/... -m "not slow and not connected".

Heads-up: the pyproject default addopts exclude only slow (-m 'not slow') — bare pytest WILL collect connected tests, so pass -m "not slow and not connected" explicitly when no broker is running.

Global pytest timeout is 30s per test; the suite runs parallel — keep tests independent and use the queue fixture for unique names.

Markers — strict

--strict-markers is enabled; the allowed set is defined in pyproject.toml (kafka, confluent, rabbit, nats, redis, redis_cluster, mqtt, slow, connected, all, benchmark).

Broker-specific test → its broker mark: @pytest.mark.kafka().
Talks to a real broker over the network → add @pytest.mark.connected() (excluded by just test; bare pytest excludes only slow by default).
Slow test → @pytest.mark.slow() (also excluded by default).
Async test → @pytest.mark.asyncio().

Shared base testcases

Cross-broker behavior is specified ONCE in tests/brokers/base/ (basic.py, consume.py, publish.py, router.py, codec.py, middlewares.py, parser.py, requests.py, connection.py, fastapi.py, testclient.py, ...) and inherited by every broker.

Each broker defines its config in tests/brokers/<broker>/basic.py:

class KafkaTestcaseConfig(BaseTestcaseConfig):
    def get_broker(self, apply_types: bool = False, **kwargs: Any) -> KafkaBroker:
        return KafkaBroker(apply_types=apply_types, **kwargs)

    def get_router(self, **kwargs: Any) -> KafkaRouter:
        return KafkaRouter(**kwargs)


class KafkaMemoryTestcaseConfig(KafkaTestcaseConfig):
    def patch_broker(self, *brokers: KafkaBroker, **kwargs: Any) -> TestKafkaBroker:
        return TestKafkaBroker(*brokers, **kwargs)

Test classes multiply-inherit config + behavior suite:

@pytest.mark.kafka()
class TestKafkaCodec(KafkaMemoryTestcaseConfig, CodecTestcase): ...


@pytest.mark.connected()
@pytest.mark.kafka()
class TestConsume(KafkaTestcaseConfig, BrokerRealConsumeTestcase): ...

Rule: new cross-broker behavior goes into a base class in tests/brokers/base/ so every broker inherits the test. Broker-specific behavior is tested directly in tests/brokers/<broker>/.

In-memory vs real broker

Default to the in-memory TestBroker (faststream/<broker>/testing.py) via a *MemoryTestcaseConfig — fast, runs everywhere, no connected mark.
Use a real broker (plain *TestcaseConfig + @pytest.mark.connected()) when the behavior depends on actual broker semantics (acks, consumer groups, reconnects). Connection settings come from the Settings dataclass in tests/brokers/<broker>/conftest.py.

Fixtures & utilities

Global fixtures (tests/conftest.py): queue (unique uuid string), event (asyncio.Event), mock / async_mock (function-scoped, reset via teardown), context, runner (CLI).
tests/marks.py: conditional skips — skip_windows, skip_macos, pydantic_v1/pydantic_v2, require_aiokafka, require_confluent, require_aiopika, require_redis, require_nats, require_mqtt.
tests/tools.py: spy_decorator — wraps a real method with a mock spy (call assertions via .mock) while preserving behavior.
tests/mocks.py: mock_pydantic_settings_env for env-driven settings tests.
dirty-equals and freezegun are available as test deps.

Related skills

dev-workflow — docker broker management and the full just recipe matrix.
code-architecture — where the code under test lives and how it's shaped.
documentation-writing — docs snippets get tests under tests/docs/.

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