Test demonstrating #3053: If-Modified-Since gets swallowed up by rack-cache.

railties/test/application/middleware/cache_test.rb

@@ -31,6 +31,10 @@ module ApplicationTests
             $last_modified ||= Time.now.utc
             render_conditionally(:last_modified => $last_modified)
           end
+
+          def keeps_if_modified_since
+            render :text => request.headers['If-Modified-Since']
+          end
         private
           def render_conditionally(headers)
             if stale?(headers.merge(:public => !params[:private]))
@@ -47,6 +51,16 @@ module ApplicationTests
       RUBY
     end
 
+    def test_cache_keeps_if_modified_since
+      simple_controller
+      expected = "Wed, 30 May 1984 19:43:31 GMT"
+      
+      get "/expires/keeps_if_modified_since", {}, "HTTP_IF_MODIFIED_SINCE" => expected
+      
+      assert_equal 200, last_response.status
+      assert_equal expected, last_response.body, "cache should have kept If-Modified-Since"
+    end
+
     def test_cache_is_disabled_in_dev_mode
       simple_controller
       app("development")