Testing

micro.override(*components)

Swaps components inside an active async with micro: block.

from unittest.mock import AsyncMock

from grelmicro import Grelmicro
from grelmicro.sync import Sync
from grelmicro.sync.abc import SyncBackend


async def test_swap_for_block(micro: Grelmicro) -> None:
    fake_backend = AsyncMock(spec=SyncBackend)
    async with micro:
        async with micro.override(Sync(fake_backend)):
            await do_something_that_uses_sync()
            fake_backend.acquire.assert_awaited()

Override components are entered when the block opens and exited in reverse order when it closes. Prior registrations are restored on exit, including when the block raises.

Restrictions

• Only Component instances can be overridden. Plain async context managers passed to use(...) are substituted at construction time, not through override().
• Calling micro.override(...) outside an active async with micro: raises OutOfContextError.

Pytest recipe

grelmicro ships no pytest plugin. Add a micro fixture in conftest.py:

from collections.abc import AsyncIterator

import pytest

from grelmicro import Grelmicro
from grelmicro.cache import Cache
from grelmicro.cache.memory import MemoryCacheAdapter
from grelmicro.sync import Sync
from grelmicro.sync.memory import MemorySyncAdapter


@pytest.fixture
async def micro() -> AsyncIterator[Grelmicro]:
    app = Grelmicro(uses=[
        Sync(MemorySyncAdapter()),
        Cache(MemoryCacheAdapter()),
    ])
    async with app:
        yield app

Tests then read micro as a fixture and apply per-case overrides:

from unittest.mock import AsyncMock

from grelmicro import Grelmicro
from grelmicro.sync import Sync
from grelmicro.sync.abc import SyncBackend


async def test_login(micro: Grelmicro) -> None:
    fake_backend = AsyncMock(spec=SyncBackend)
    async with micro.override(Sync(fake_backend)):
        await do_login("u1")