Java Haiku: Forever

public class Forever {

    public void forever() {

        ever = true;

        for(;ever;);

    }

}

 

Creating AWS resources in pytest fixtures with moto

 When unit testing functions that access AWS resources, the easiest way is to use the moto library. For instance, I have to test several functions that access an SQS queue, so I proceed this way:

import boto3

from moto import mock_sqs

def create_queue():

    client = boto3.client("sqs")

    queue_url = client.create_queue(QueueName="queue")["QueueUrl"]

    sqs = boto3.resource("sqs")

    return sqs.Queue(queue_url)

@mock_sqs

def test_something()

    queue = create_queue()

    ...

Since I had this create_queue() call at the beginning of most of my test functions, I wanted to make it a fixture. So i tried this way:

import boto3

from moto import mock_sqs

from pytest import fixture

@fixture

@mock_sqs

def queue():

    client = boto3.client("sqs")

    queue_url = client.create_queue(QueueName="queue")["QueueUrl"]

    sqs = boto3.resource("sqs")

    return sqs.Queue(queue_url)

@mock_sqs

def test_something(queue)

    ...

Unfortunately, this raised an error in my test functions stating that the queue does not exist. The reason for it is that the decorator @mock_sqs on the fixture would destroy my SQS queue as soon as it would leave the queue() method.

The solution is simple: do not use the mock as a decorator, but trigger it when the fixture is initializing and destroy it when it terminates. That means using a yield within the fixture to return the queue:

import boto3

from moto import mock_sqs

from pytest import fixture

@fixture

def queue():

    mock_sqs().start()

    client = boto3.client("sqs")

    queue_url = client.create_queue(QueueName="queue")["QueueUrl"]

    sqs = boto3.resource("sqs")

    yield sqs.Queue(queue_url)

    

    mock_sqs().stop()

def test_something(queue)

    ...

Notice that we have to drop the decorator on the test function as well.

Thanks for the answers to this moto issue.