Do not clear HTTP_COOKIES header after request

actionpack/lib/action_controller/test_case.rb

@@ -514,8 +514,6 @@ def process(action, method: "GET", params: {}, session: nil, body: nil, flash: {
           @request = @controller.request
           @response = @controller.response
 
-          @request.delete_header "HTTP_COOKIE"
-
           if @request.have_cookie_jar?
             unless @request.cookie_jar.committed?
               @request.cookie_jar.write(@response)

actionpack/test/dispatch/cookies_test.rb

@@ -272,6 +272,10 @@ def string_key_mock
     def noop
       head :ok
     end
+
+    def encrypted_cookie
+      cookies.encrypted["foo"]
+    end
   end
 
   tests TestController
@@ -1189,6 +1193,12 @@ def test_cookies_precedence_over_request_cookies
     assert_equal "david", cookies[:user_name]
   end
 
+  def test_cookies_are_not_cleared
+    cookies.encrypted["foo"] = "bar"
+    get :noop
+    assert_equal "bar", @controller.encrypted_cookie
+  end
+
   private
     def assert_cookie_header(expected)
       header = @response.headers["Set-Cookie"]