The name headers and its placement just below with_mock_header can create confusion as to whether these two keys are related.

• headers to response_headers?
• add comment -- specify response headers.

1. remove the core.log.warn?
2. use ngx.header[key] = value instead? keep the same as line 227

Using core.response is more efficient.

Need a blank

What happens if you set 2 identical response headers? Add a test case

What do you mean by "identical response headers"?

1. Only the last one is retained, the first one is lost. However, if someone needs multiple values for a header they can do "header-name": "val1, val2".

2. Why is this test case needed?

You could test, I don't think you are right.

I don't think you are right.

Well, you can give it a try on your local machine 😀

P.S.: I pushed a new commit that would demonstrate the addition of multiple values for a header.

I said this because you use the function core.response.add_header to add the response header, the function will append the value to the same header name, but i tested locally, and found that the conf.response_headers won't pass the duplicated headers.
If we pass

                                   "response_headers": {
                                        "X-Apisix": "is-cool",
                                        "X-Apisix": "yes"
                                    }

we will get

                                   "response_headers": {
                                        "X-Apisix": "yes"
                                    }

So it's ok for this.
But i don't see you example