Sedastub

Sedastub is a lightweight, open-source library designed to provide configurable stub components for testing and simulation of software systems. It enables developers to emulate external services, subsystems, or interfaces without requiring complete implementations. By offering ready-made, adjustable placeholders, sedastub helps teams reproduce real-world interactions, validate integration points, and explore failure modes in a repeatable manner.

The project emphasizes simplicity and reproducibility, with stubs defined as modular blocks that can be composed into service graphs. Each stub can model latency, throughput, and a range of error conditions, enabling ballast testing and what-if analysis. Sedastub also supports scripted scenarios, configurable data inputs, and basic observability for timing and error statistics.

Implementations exist in multiple languages, with common pieces available for Python and JavaScript/Node.js. Stubs can run as standalone services or be containerized for use in CI pipelines and local development. The library provides a small API for configuring responses, chaining stubs, and exporting traces to popular tracing systems.

Typical use cases include simulating downstream services in microservice architectures, testing fault-tolerance strategies, and validating deployment pipelines against failure scenarios without impacting real systems.

Sedastub originated in a small open-source community in the early 2020s. It has seen modest adoption in education and hobby projects and maintains an active but niche ecosystem with community contributions and ongoing feature requests.

See also: mocks, stubs, service virtualization, chaos engineering.