Faultsense

Faultsense is an assertion layer for end-to-end testing that runs in real browsers on real users, allowing developers to write assertions directly in HTML markup. It solves the problem of testing only in staging by continuously validating user flows in production without performance impact. It targets developers and engineering teams in companies of all sizes, particularly those using web frameworks. It is positioned as a hybrid of E2E testing and real user monitoring, with no driver or backend lock-in, and is open source.

Key features

• Write assertions as HTML attributes
• Runs in production on real users
• No performance impact (1.7KB idle heap)
• Supports any web framework
• AI agent drives flows in staging
• Real users drive flows in production
• Streams results to your stack
• Open source, no lock-in