Pollyjs is an HTTP mocking and recording library designed to capture and replay network interactions to create deterministic tests. It functions as a request interceptor and stubbing framework that records real API responses into files, ensuring consistent test results across different environments without relying on live network servers.
The tool utilizes pluggable network adapters to support various environments and employs a state-based mode switching system to toggle between recording, replaying, and stubbing behaviors. It uses pattern-based request matching and persistent interaction storage to serve identical responses to incoming requests.
The library covers a broad range of API integration capabilities, including network traffic simulation and the management of request flows. It provides mechanisms for returning custom status codes and mocked data to test edge cases and validate application behavior during automated integration testing.