fakecloud 0.9.0

Python SDK for fakecloud — local AWS cloud emulator

fakecloud

Python SDK for fakecloud — a local AWS cloud emulator.

This package provides async and sync clients for the fakecloud introspection and simulation API (/_fakecloud/* endpoints), letting you inspect sent emails, published messages, Lambda invocations, and more from your tests.

Installation

pip install fakecloud

Quick start

Async

import asyncio
from fakecloud import FakeCloud

async def main():
    async with FakeCloud("http://localhost:4566") as fc:
        # Check server health
        health = await fc.health()
        print(health.status, health.version)

        # List sent SES emails
        emails = await fc.ses.get_emails()
        for email in emails.emails:
            print(f"{email.from_addr} -> {email.to}: {email.subject}")

        # List SNS messages
        messages = await fc.sns.get_messages()
        for msg in messages.messages:
            print(f"{msg.topic_arn}: {msg.message}")

        # Inspect Lambda invocations
        invocations = await fc.lambda_.get_invocations()
        for inv in invocations.invocations:
            print(f"{inv.function_arn}: {inv.payload}")

        # Reset all state between tests
        await fc.reset()

asyncio.run(main())

Sync

from fakecloud import FakeCloudSync

with FakeCloudSync("http://localhost:4566") as fc:
    health = fc.health()
    print(health.status)

    emails = fc.ses.get_emails()
    for email in emails.emails:
        print(email.subject)

API reference

FakeCloud / FakeCloudSync

Top-level client. Pass base_url (default http://localhost:4566).

Method	Description
health()	Server health check
reset()	Reset all service state
reset_service(service)	Reset a single service

Service sub-clients

Access via properties on the main client:

Property	Service	Methods
lambda_	Lambda	get_invocations(), get_warm_containers(), evict_container(name)
ses	SES	get_emails(), simulate_inbound(req)
sns	SNS	get_messages(), get_pending_confirmations(), confirm_subscription(req)
sqs	SQS	get_messages(), tick_expiration(), force_dlq(queue_name)
events	EventBridge	get_history(), fire_rule(req)
s3	S3	get_notifications(), tick_lifecycle()
dynamodb	DynamoDB	tick_ttl()
secretsmanager	SecretsManager	tick_rotation()
cognito	Cognito	get_user_codes(pool_id, username), get_confirmation_codes(), confirm_user(req), get_tokens(), expire_tokens(req), get_auth_events()
rds	RDS	get_instances()
elasticache	ElastiCache	get_clusters(), get_replication_groups(), get_serverless_caches()
stepfunctions	Step Functions	get_executions()
apigatewayv2	API Gateway v2	get_requests()
bedrock	Bedrock Runtime	get_invocations(), set_model_response(model_id, text), set_response_rules(model_id, rules), clear_response_rules(model_id), queue_fault(rule), get_faults(), clear_faults()

Testing Bedrock-calling code end-to-end

from fakecloud import FakeCloudSync
from fakecloud.types import BedrockResponseRule, BedrockFaultRule

fc = FakeCloudSync()
model_id = "anthropic.claude-3-haiku-20240307-v1:0"


def test_classifier_branches_on_spam_vs_ham():
    fc.reset()
    fc.bedrock.set_response_rules(
        model_id,
        [
            BedrockResponseRule(prompt_contains="buy now", response='{"label":"spam"}'),
            BedrockResponseRule(prompt_contains=None, response='{"label":"ham"}'),
        ],
    )

    classify("hello friend")           # user code that calls Bedrock
    classify("buy now cheap pills")

    invocations = fc.bedrock.get_invocations().invocations
    assert len(invocations) == 2
    assert "ham" in invocations[0].output
    assert "spam" in invocations[1].output


def test_retries_on_throttling():
    fc.reset()
    fc.bedrock.queue_fault(
        BedrockFaultRule(
            error_type="ThrottlingException",
            message="Rate exceeded",
            http_status=429,
            count=1,  # only the first call faults; the retry succeeds
        )
    )

    classify("hello")

    invocations = fc.bedrock.get_invocations().invocations
    assert len(invocations) == 2
    assert "ThrottlingException" in (invocations[0].error or "")
    assert invocations[1].error is None

Error handling

All methods raise FakeCloudError on non-2xx responses:

from fakecloud.client import FakeCloudError

try:
    await fc.health()
except FakeCloudError as e:
    print(e.status, e.body)

pytest fixture example

import pytest
from fakecloud import FakeCloudSync

@pytest.fixture(autouse=True)
def reset_fakecloud():
    fc = FakeCloudSync()
    fc.reset()
    yield fc
    fc.close()

def test_email_sent(reset_fakecloud):
    # ... your code that sends an email via SES ...
    emails = reset_fakecloud.ses.get_emails()
    assert len(emails.emails) == 1
    assert emails.emails[0].subject == "Welcome"