Steno is a tool for recording and replaying HTTP requests and responses, to and from the Slack Platform, in order to generate testing fixtues for a Slack App.
In record mode, Steno is a two-way HTTP proxy that captures each request and response that passes through it (initiated from either the Slack App or the Slack Platform) and writes them to disk as scenarios.
In replay mode, Steno behaves as a stub for the Slack Platform by responding to HTTP requests from the Slack App, or by creating HTTP requests for your Slack App to handle. In this mode Steno also allows the developer to make assertions on each interaction in order to verify the behavior of the Slack App.