What Ruby, Rails and RSpec versions are you using?

Ruby version: 3.3.3
Rails version: 7.1.3.4
RSpec version: 3.13.0
Rack version: 3.1.3

Observed behaviour

Rack has recently changed the name of the 422 status code from unprocessable_entity to unprocessable_content. However, both names will still resolve if Rack's public API is being used. However, the HttpStatusMatcher is looking at the Rack Constant directly, instead of using the provided API.

My suggestion is for the code in have_http_status.rb that looks like (around line 218)...

def set_expected_code!
  @expected ||=
    Rack::Utils::SYMBOL_TO_STATUS_CODE.fetch(expected_status) do
      raise ArgumentError,
            "Invalid HTTP status: #{expected_status.inspect}"
    end
end

be changed to....

def set_expected_code!
  @expected ||= Rack::Utils.status_code(expected_status)
end

Here's the behavior of the Rack::Utils.status_code method...

irb> Rack::Utils.status_code(:unprocessable_content)
  => 422
irb> Rack::Utils.status_code(:unprocessable_entity)
  => 422
irb> Rack::Utils.status_code(:invalidcode)
(irb):4:in `<main>': Unrecognized status code :invalidcode (ArgumentError)