testland/pytest-asyncio-patterns

Configures and runs async Python tests with pytest-asyncio: installs the plugin, selects asyncio_mode (auto vs strict), scopes event loops (function/class/module/session), writes async fixtures with @pytest_asyncio.fixture, mocks coroutines with AsyncMock, and tests FastAPI (httpx.AsyncClient + ASGITransport) and aiohttp (aiohttp_client fixture) applications. Use when a Python project contains async def test_ functions, FastAPI/aiohttp endpoints, or any asyncio-based code that needs pytest integration. Do NOT use for general pytest fixture design, parametrize patterns, or conftest.py structure without an asyncio-specific problem (event-loop scoping, mode config, AsyncMock, ASGI client): use python-unit-tests for those.

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AsyncMock await assertions and side_effect

Name: testland/pytest-asyncio-patterns
Rating: 93 (1 reviews)
Author: testland

Await-specific assertions and side_effect semantics for unittest.mock.AsyncMock (stdlib since Python 3.8). The SKILL.md spine keeps the primary AsyncMock example; the exhaustive assertion reference is here.

Source: docs.python.org AsyncMock.

Patch an async method on an import path

@pytest.mark.asyncio
async def test_external_call():
    with patch("myapp.clients.redis.get", new_callable=AsyncMock) as mock_get:
        mock_get.return_value = b"cached"
        result = await fetch_from_cache("key")
    mock_get.assert_awaited_once_with("key")
    assert result == b"cached"

new_callable=AsyncMock is required so patch installs a coroutine-returning mock rather than a plain MagicMock.

Await-specific assertions

Assertion	Meaning
`assert_awaited_once_with(a, *kw)`	Awaited exactly once with these args
`assert_awaited_with(a, *kw)`	Last await had these args
`assert_any_await(a, *kw)`	Ever awaited with these args
`assert_not_awaited()`	Never awaited
`await_count`	How many times awaited (attribute, not assertion)

The assert_called_* family checks that the mock was called, not that it was awaited; a coroutine mock can be called without being awaited, so prefer the assert_awaited_* family for async code.

side_effect on AsyncMock

side_effect on AsyncMock behaves the same as on a sync mock: a callable is invoked and its result returned; an exception class (or instance) is raised when the mock is awaited; an iterable returns successive values on each await.