CloudFormation

Overview

CloudMock emulates AWS CloudFormation stack management, supporting stack lifecycle, template validation, resource listing, change sets, and exports. Stack resources are stored as metadata — CloudFormation does not create actual resources in the emulator.

Supported Operations

Operation	Status	Notes
CreateStack	Supported	Creates a stack from a template
DeleteStack	Supported	Deletes a stack
DescribeStacks	Supported	Returns stack metadata and outputs
ListStacks	Supported	Returns stack summaries with optional status filter
DescribeStackResources	Supported	Returns the resources in a stack
DescribeStackEvents	Supported	Returns the event history for a stack
GetTemplate	Supported	Returns the template body for a stack
ValidateTemplate	Supported	Validates a template and returns parameter names
ListExports	Supported	Returns all stack exports
CreateChangeSet	Supported	Creates a change set for a stack
DescribeChangeSet	Supported	Returns change set details
ExecuteChangeSet	Supported	Applies a change set to a stack
DeleteChangeSet	Supported	Discards a change set

Quick Start

curl

# Validate a template
curl -X POST "http://localhost:4566/?Action=ValidateTemplate&TemplateBody=%7B%22AWSTemplateFormatVersion%22%3A%222010-09-09%22%7D"

# Create a stack
curl -X POST "http://localhost:4566/?Action=CreateStack&StackName=my-stack&TemplateBody=%7B%22AWSTemplateFormatVersion%22%3A%222010-09-09%22%7D"

Node.js

import { CloudFormationClient, CreateStackCommand, DescribeStacksCommand } from '@aws-sdk/client-cloudformation';

const cf = new CloudFormationClient({
  endpoint: 'http://localhost:4566',
  region: 'us-east-1',
  credentials: { accessKeyId: 'test', secretAccessKey: 'test' },
});

await cf.send(new CreateStackCommand({
  StackName: 'infra',
  TemplateBody: JSON.stringify({
    AWSTemplateFormatVersion: '2010-09-09',
    Resources: {
      MyBucket: { Type: 'AWS::S3::Bucket', Properties: { BucketName: 'my-cf-bucket' } },
    },
  }),
}));

const { Stacks } = await cf.send(new DescribeStacksCommand({ StackName: 'infra' }));
console.log(Stacks?.[0]?.StackStatus); // CREATE_COMPLETE

Python

import boto3

cf = boto3.client('cloudformation', endpoint_url='http://localhost:4566',
                  aws_access_key_id='test', aws_secret_access_key='test',
                  region_name='us-east-1')

template = """
AWSTemplateFormatVersion: '2010-09-09'
Parameters:
  BucketName:
    Type: String
Resources:
  MyBucket:
    Type: AWS::S3::Bucket
    Properties:
      BucketName: !Ref BucketName
Outputs:
  BucketArn:
    Value: !GetAtt MyBucket.Arn
"""

cf.create_stack(
    StackName='infra', TemplateBody=template,
    Parameters=[{'ParameterKey': 'BucketName', 'ParameterValue': 'my-cf-bucket'}],
)

response = cf.describe_stacks(StackName='infra')
print(response['Stacks'][0]['StackStatus'])  # CREATE_COMPLETE

Configuration

cloudmock.yml

services:
  cloudformation:
    enabled: true

No additional service-specific configuration is required.

Known Differences from AWS

• Stack resources listed in the template are stored as metadata only. CloudFormation does not create actual resources (e.g., an AWS::S3::Bucket in the template does not create a real S3 bucket).
• Stacks immediately transition to CREATE_COMPLETE after CreateStack.
• Change sets transition to CREATE_COMPLETE immediately and can be executed without waits.
• Nested stacks, stack sets, and drift detection are not implemented.
• Intrinsic functions (!Ref, !GetAtt, etc.) are not evaluated.

Error Codes

Code	HTTP Status	Description
ValidationError	400	The template or parameters are not valid
AlreadyExistsException	400	A stack with this name already exists
ChangeSetNotFound	404	The specified change set does not exist
InsufficientCapabilitiesException	400	Required capabilities were not acknowledged