Ask HN: Any open source alternatives to Postman or Assertible?

I assumed something like this would be there, but apparently there are none. Are there any Postman or Assertible open source web alternative ? Prefer something which can deployed to Heroku. Not looking for an native or chrome app.

Looks like they only have Mac/Linux/Windows App. I was hoping something i can just deploy on Heroku or host it on any server.