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Celery 5 tasks, chains and groups tested in eager mode: working versions (tested 2026-10-15)

Define Celery tasks, chain and fan them out with groups, then test them offline with task_always_eager and the in-memory broker.

passed4 passed · 0 failed2026-10-15 11:34 UTC
Status
passed
Last passed
2026-10-15 11:34 UTC
Tests
4 / 4
Language
Python
Runtime
Python 3.13.16
pinned versions2
celery@5.6.3pytest@9.1.1
run it
uv venv -q .venv && uv pip install -q --python .venv/bin/python -r requirements.txt
.venv/bin/python -m pytest -q
test environment
Python 3.13.16
linux 6.17.0-1022-azure
x64
runner: github-actions 38728226240

The code

Exactly the files that passed. Your agent can pull them with get_recipe("celery-tasks-eager-testing") (install), or see them on GitHub.

requirements.txt
celery==5.6.3
pytest==9.1.1
tasks.py
from celery import Celery, chain, group

app = Celery("tasks", broker="memory://", backend="cache+memory://")

@app.task
def add(x, y):
    return x + y

@app.task
def double(x):
    return x * 2

def add_then_double(x, y):
    return chain(add.s(x, y), double.s())

def sum_of_doubles(nums):
    # fan out with a group, then reduce the results
    return sum(group(double.s(n) for n in nums).apply_async().get())
tests/test_tasks.py
import pytest
from tasks import app, add, add_then_double, sum_of_doubles

@pytest.fixture(autouse=True)
def eager():
    app.conf.update(task_always_eager=True, task_eager_propagates=True)
    yield
    app.conf.update(task_always_eager=False)

def test_delay():
    assert add.delay(2, 3).get() == 5

def test_chain():
    assert add_then_double(2, 3).apply_async().get() == 10

def test_group():
    assert sum_of_doubles([1, 2, 3]) == 12

def test_errors_propagate():
    with pytest.raises(TypeError):
        add.delay(1, "a").get()
pytest.ini
[pytest]
pythonpath = .

Connect to ProvenPin

Add the free MCP server so your agent can pull this recipe and others like it. Same setup as the docs.

terminal
claude mcp add --transport http provenpin https://mcp.provenpin.com/mcp

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