added the cookie plugin, with the first test: passing the cookie in the options

lib/httpx/plugins/cookies.rb

@@ -0,0 +1,50 @@
+# frozen_string_literal: true
+
+module HTTPX
+  module Plugins
+    module Cookies
+      def self.load_dependencies(*)
+        require "http/cookie"
+      end
+
+      module InstanceMethods
+        def cookies(cookies)
+          branch(default_options.with_cookies(cookies))
+        end
+      end
+
+      module RequestMethods
+        def initialize(*)
+          super
+          @headers.cookies(@options.cookies)
+        end
+      end
+
+      module HeadersMethods
+        def cookies(cookies)
+          cookies.each do |k, v|
+            cookie = k.is_a?(HTTP::Cookie) ? k : HTTP::Cookie.new(k.to_s, v.to_s)
+            add("cookie", cookie.cookie_value)
+          end
+        end
+      end
+
+      module ResponseMethods
+        def cookies
+          headers["cookie"]
+        end
+      end
+
+      module OptionsMethods
+        def self.included(klass)
+          super
+          klass.def_option(:cookies) do |cookies|
+            cookies.split(/ *; */) if cookies.is_a?(String)
+            cookies
+          end
+        end
+      end 
+    end
+    register_plugin :cookies, Cookies 
+  end
+end

test/http1_test.rb

@@ -13,6 +13,8 @@ class HTTP1Test < HTTPTest
   include ResponseBody 
   include IO 
   
+  include Plugins::Cookies 
+  
   private
 
   def origin

test/http2_test.rb

@@ -11,6 +11,8 @@ class HTTP2Test < HTTPTest
   include ResponseBody 
   include IO 
   
+  include Plugins::Cookies
+
   private
 
   def origin

test/support/requests/plugins/cookies.rb

@@ -0,0 +1,29 @@
+# frozen_string_literal: true
+
+module Requests
+  module Plugins
+    module Cookies
+
+      def test_plugin_cookies
+        client = HTTPX.plugin(:cookies)
+        assert client.respond_to?(:cookies), "client should be cookie-enabled"
+        response = client.get(cookies_uri)
+        assert response.respond_to?(:cookies), "response should have cookies"
+        body = json_body(response)
+        assert body.key?("cookies")
+        assert body["cookies"].empty?
+
+        session_response = client.cookies("abc" => "def").get(cookies_uri)
+        body = json_body(session_response)
+        assert body.key?("cookies")
+        assert body["cookies"]["abc"] == "def", "abc wasn't properly set"
+      end
+
+      private
+
+      def cookies_uri
+        build_uri("/cookies")
+      end
+    end
+  end
+end