Chain of Responsibility

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invocations shows CardHandler entered and CashHandler not entered. There is no separate chain bus. handled contains an event only from the step that returned.

See Chain of Responsibility.

class CardHandler(cqrs.handlers.CORRequestHandler[PayOrder]):
    async def handle(self, request: PayOrder):
        if request.method != "card":
            return await self.next(request)
        return Paid(method="card")

def commands_mapper(mapper: cqrs.RequestMap) -> None:
    mapper.bind(PayOrder, [CardHandler, CashHandler])

result = await harness.mediator.send(PayOrder(method="card"))
assert result.method == "card"
harness.invocations.assert_entered(CardHandler)
harness.invocations.assert_not_entered(CashHandler)

Library example: examples/testing/chain.py.