Slack proxy for sending messages locally for development purposes

[TomaszBorczyk]

Background:
I am taking over an existing slack based application that uses socket mode communication with slack. To test the functionality locally before pushing to a live environment, I would like to run the app locally and proxy it to a mock slack server. Ideally, I imagine it would work as follows:

• proxy app runs as an imitation of slack backend
• the main consumer app runs with minimal config changed (eg with slack api url changed)
• consumer app can send messages to the proxy
• I can trigger fake messages from the proxy to the consumer app

Question:
Is there any built in mechanism or a simple way to achieve above?