Improve ActionController::TestCase to expose a binary encoded `requ…

…est.body`.

The rack spec clearly states:

> The input stream is an IO-like object which contains the raw HTTP POST data.
> When applicable, its external encoding must be “ASCII-8BIT” and it must be opened in binary mode.

Until now its encoding was generally UTF-8, which doesn't accurately reflect production
behavior.

actionpack/CHANGELOG.md

@@ -1,3 +1,15 @@
+*   Improve `ActionController::TestCase` to expose a binary encoded `request.body`.
+
+    The rack spec clearly states:
+
+    > The input stream is an IO-like object which contains the raw HTTP POST data.
+    > When applicable, its external encoding must be “ASCII-8BIT” and it must be opened in binary mode.
+
+    Until now its encoding was generally UTF-8, which doesn't accurately reflect production
+    behavior.
+
+    *Jean Boussier*
+
 *   Update `ActionController::AllowBrowser` to support passing method names to `:block`
 
     ```ruby

actionpack/lib/action_controller/test_case.rb

@@ -123,7 +123,7 @@ def assign_parameters(routes, controller_path, action, parameters, generated_pat
           end
         end
 
-        data_stream = StringIO.new(data)
+        data_stream = StringIO.new(data.b)
         set_header "CONTENT_LENGTH", data_stream.length.to_s
         set_header "rack.input", data_stream
       end

actionpack/test/controller/test_case_test.rb

@@ -53,6 +53,11 @@ def render_body
       render plain: request.body.read
     end
 
+    def render_body_encoding
+      request.body.rewind
+      render plain: request.body.read.encoding.name
+    end
+
     def test_params
       render plain: ::JSON.dump(params.to_unsafe_h)
     end
@@ -270,6 +275,14 @@ def test_body_stream
     assert_equal params.to_query, @response.body
   end
 
+  def test_body_stream_is_binary
+    params = Hash[:page, { name: "page name" }, "some key", 123]
+
+    post :render_body_encoding, params: params.dup
+
+    assert_equal Encoding::BINARY.name, @response.body
+  end
+
   def test_document_body_and_params_with_post
     post :test_params, params: { id: 1 }
     assert_equal({ "id" => "1", "controller" => "test_case_test/test", "action" => "test_params" }, ::JSON.parse(@response.body))