1 files changed, 55 insertions, 0 deletions
diff --git a/actionpack/lib/action_dispatch/testing/request_encoder.rb b/actionpack/lib/action_dispatch/testing/request_encoder.rb
new file mode 100644
index 0000000000..01246b7a2e
--- /dev/null
+++ b/actionpack/lib/action_dispatch/testing/request_encoder.rb
@@ -0,0 +1,55 @@
+# frozen_string_literal: true
+
+module ActionDispatch
+  class RequestEncoder # :nodoc:
+    class IdentityEncoder
+      def content_type; end
+      def accept_header; end
+      def encode_params(params); params; end
+      def response_parser; -> body { body }; end
+    end
+
+    @encoders = { identity: IdentityEncoder.new }
+
+    attr_reader :response_parser
+
+    def initialize(mime_name, param_encoder, response_parser)
+      @mime = Mime[mime_name]
+
+      unless @mime
+        raise ArgumentError, "Can't register a request encoder for " \
+          "unregistered MIME Type: #{mime_name}. See `Mime::Type.register`."
+      end
+
+      @response_parser = response_parser || -> body { body }
+      @param_encoder   = param_encoder   || :"to_#{@mime.symbol}".to_proc
+    end
+
+    def content_type
+      @mime.to_s
+    end
+
+    def accept_header
+      @mime.to_s
+    end
+
+    def encode_params(params)
+      @param_encoder.call(params)
+    end
+
+    def self.parser(content_type)
+      mime = Mime::Type.lookup(content_type)
+      encoder(mime ? mime.ref : nil).response_parser
+    end
+
+    def self.encoder(name)
+      @encoders[name] || @encoders[:identity]
+    end
+
+    def self.register_encoder(mime_name, param_encoder: nil, response_parser: nil)
+      @encoders[mime_name] = new(mime_name, param_encoder, response_parser)
+    end
+
+    register_encoder :json, response_parser: -> body { JSON.parse(body) }
+  end
+end