Locust
Locust is an open-source load testing tool written in Python that allows developers to simulate millions of concurrent users to test the performance and scalability of web applications and APIs. It uses a code-based approach where test scenarios are defined in Python scripts, making it highly flexible and programmable. The tool provides real-time statistics through a web-based UI and can be distributed across multiple machines for large-scale testing.
Developers should use Locust when they need to perform load, stress, or performance testing on web services, especially in agile or DevOps environments where tests need to be integrated into CI/CD pipelines. It is ideal for testing REST APIs, web applications, and microservices because its Python-based scripting allows for complex user behavior simulation and easy integration with other Python libraries. Use cases include identifying performance bottlenecks, validating scalability under high traffic, and ensuring service reliability before deployment.