@mikekelly WebMock tries to normalize headers to have unified version for comparison with stubs.

What exactly is the issue you have problems with?

I'm stubbing a response which has a header called x-my_header but the webmock response renames it tox-my-header which breaks my client. I'm unable to simulate response headers with underscores

@mikekelly I see. You're right, WebMock should not do that.

Do you know why the behaviour was added in the first place?

Do you need someone to propose a solution in a PR?

Right now I am using a monkey patch which resolves this issue, I could re-use that.

It was added to ensure unified format of headers i.e. if case someone declares 'content_type' in the response.

It's wasn't the best approach though.

@mikekelly I made a pull request with some hacky code to get specs around how we are normalizing headers right now. Can you write a spec that fits you use case.

If you don't get to it, I'll take a stab when I have some time.
#482

It's a huge problem!!! My temporary solution:
/config/initializers/webmoch_rewrite.rb

# frozen_string_literal: true
if defined? WebMock::Response
  WebMock::Response.class_eval do
    def headers=(headers)
      @headers = headers
      if @headers && !@headers.is_a?(Proc) # rubocop:disable Style/GuardClause
        @headers =
          if @headers.key?(:skip_normalize)
            @headers.except(:skip_normalize)
          else
            WebMock::Util::Headers.normalize_headers(@headers)
          end
      end
    end
  end
end