serverlessspy.com

What It Is

ServerlessSpy is a CDK-based testing tool for AWS Serverless architectures. Its core goal is to make integration tests faster and easier to debug. Through a CDK construct, it creates interception infrastructure in development or test environments, captures events from Lambda, SNS, SQS, EventBridge, DynamoDB, S3, and more, then pushes them via AWS IoT WebSockets to the test library or a local Web Console.

Core Capabilities

Its biggest differentiator is “event push” rather than repeated polling from the test side, which makes it faster to determine whether an asynchronous workflow has completed. The testing library has built-in Jest integration and can also be used with other testing libraries. The sample code demonstrates event waiting and assertion patterns such as waitForEventBridge, waitForSns, waitForSqs, waitForFunction, and waitForDynamoDB. TypeScript is strongly encouraged and provides a better strongly typed experience. The Web Console lets you view events locally in real time and supports regex search, making it useful for debugging Serverless event flows.

Support Scope and Limitations

ServerlessSpy only works with infrastructure created by CDK; this is a hard requirement. It currently supports Node.js and Python stacks, with no plans to support other language stacks, though contributions are welcome. API Gateway and AppSync do not directly support event interception because the available interception methods depend on CloudWatch and are relatively slow; in practice, you can observe the flow after events enter supported services such as Lambda. It is also not a distributed tracing product and cannot replace tools such as AWS X-Ray, Lumigo, or Epsagon.

Pricing and Deployment

The main documentation does not provide commercial pricing. The project page includes open-source project information such as a License and Contributing Guide. Costs mainly come from the AWS resources it creates and invokes. The FAQ states that these costs are usually negligible in low-traffic development/test environments, but production and high-load environments should be explicitly excluded; otherwise, costs may increase and AWS quotas such as Lambda concurrency may be affected. The Web Console only runs locally for now, with no cloud-hosted version available.

Pros, Cons, and Who It’s For

Its strengths are precise positioning, fast test execution, TypeScript friendliness, a good real-time visual debugging experience, and documentation that covers Quick Start, individual AWS services, FAQ, sample applications, and roadmap. Its drawbacks are its dependence on CDK, limited language stack support, unsuitability for production, and lack of full end-to-end tracing. It is best suited to teams already building Serverless applications with AWS CDK and looking to improve integration test efficiency in CI/CD.

Access from China

The main documentation does not provide information about access from mainland China, payments, or mirrors, so the China access situation is unknown. Since the tool depends on AWS IoT WebSockets and AWS resources, the actual experience will also be affected by the selected AWS region, network connectivity, and the team’s cloud account policies. Alternatives to consider include AWS X-Ray, Lumigo, Epsagon, or a self-built debugging solution based on CloudWatch.