Testing¶

potik supports two kinds of tests. A unit test calls a handler directly. An app test runs the whole runtime against a MockCluster.

Calling a handler¶

@router.handler() returns the handler unchanged, so a test can call it with plain objects in place of the record's parts, the run's context, and the results of its dependencies. It then checks the records that the handler returns. This test calls the quickstart's accept:

@pytest.mark.anyio
async def test_accept():
    record = await accept(Order(sku="A", amount=10), "c1")
    assert record == accepted(Accepted(sku="A", total=12.0), key="c1")

A plain call skips the middleware, the exception rules, and the commit.

Running the app¶

potik.testing.MockCluster runs a Kafka cluster inside the test process, so a test runs the whole app without a broker. cluster.config(config) points a config at the cluster, and cluster.wait_records() waits for the records that the app commits.

The quickstart shows a complete test. It creates the topics, sends an input with a Producer, runs the app in a task group, and waits for the output:

with MockCluster() as cluster:
    cluster.create_topic(orders)
    cluster.create_topic(accepted)
    async with Producer(cluster.bootstrap_servers) as producer:
        await producer.send(orders(Order(sku="A", amount=10), key="c1"))
    runtime = build(cluster.config(CONFIG))
    async with anyio.create_task_group() as tasks:
        await tasks.start(partial(runtime.run, handle_signals=False))
        (record,) = await cluster.wait_records(accepted, 1)
        tasks.cancel_scope.cancel()

Pass handle_signals=False in tests, and cancel the run to shut it down gracefully.

A handler that sends through a Producer in its context needs a real producer to the cluster. The test then reads the sends with wait_records(), like the outputs:

outputs = await cluster.wait_records(receipts, 1)
sends = await cluster.wait_records(audit_log, 1)

The cluster doesn't store the offsets that the app commits, so a test can't check them, or what a restarted app resumes from.