Overrides¶

The simplest (and most reliable) testing strategy is:

create a fresh diwire.Container per test
register test doubles (fakes/mocks) up front
resolve your entrypoint (service/handler) from that container

Override by registering again¶

Registrations are replaceable. In general, override before the first resolve:

from typing import Protocol

from diwire import Container, Lifetime

container = Container(autoregister=False)

class EmailClient(Protocol):
    def send(self, to: str, subject: str) -> None: ...


class RealEmailClient:
    def send(self, to: str, subject: str) -> None:
        ...


class FakeEmailClient:
    def send(self, to: str, subject: str) -> None:
        ...


container.register(EmailClient, concrete_class=RealEmailClient, lifetime=Lifetime.SINGLETON)
# In tests: override BEFORE resolving anything that depends on it.
container.register(EmailClient, concrete_class=FakeEmailClient, lifetime=Lifetime.SINGLETON)

Override using an instance (force a singleton)¶

Registering an instance is a great way to override something even if it was resolved earlier:

fake = FakeEmailClient()
container.register(EmailClient, instance=fake, lifetime=Lifetime.SINGLETON)

Because the container uses the instance directly, subsequent resolves return exactly that object.