I was playing with Microsoft Bot Framework locally which works fine if I use MSFT bot emulator for testing (both in C# .Net Core and Node.js) but I cannot figure out how to test
A bot running on localhost should be testable via any HTTP client such as Postman as long as your forming the requests correctly which really only means you just need a payload that is a valid activity representation.
What you might need to check is whether or not you have any app credentials configured on your bot when you're running in localhost. If those are set then you would need to actually properly authenticate against your localhost instance as well, which the emulator will do, but you likely don't want to do when you're just trying to hit it with something like Postman. So, just make sure to clear out the app credentials when running in localhost mode to make your life easier.
If you're not running with any app credentials, then you'll need to update your question with more details about exactly what payload your sending, how your bot is configured, etc and I'll be happy to update my answer.