1 files changed, 14 insertions, 2 deletions
diff --git a/activeresource/lib/active_resource/http_mock.rb b/activeresource/lib/active_resource/http_mock.rb
index 1ed3804017..f192c53b4f 100644
--- a/activeresource/lib/active_resource/http_mock.rb
+++ b/activeresource/lib/active_resource/http_mock.rb
@@ -148,16 +148,28 @@ module ActiveResource
     attr_accessor :path, :method, :body, :headers
 
     def initialize(method, path, body = nil, headers = {})
-      @method, @path, @body, @headers = method, path, body, headers.merge(ActiveResource::Connection::HTTP_FORMAT_HEADER_NAMES[method] => 'application/xml')
+      @method, @path, @body, @headers = method, path, body, headers
     end
 
     def ==(req)
-      path == req.path && method == req.method && headers == req.headers
+      path == req.path && method == req.method && headers_match?(req)
     end
 
     def to_s
       "<#{method.to_s.upcase}: #{path} [#{headers}] (#{body})>"
     end
+
+    private
+
+    def headers_match?(req)
+      # Ignore format header on equality if it's not defined
+      format_header = ActiveResource::Connection::HTTP_FORMAT_HEADER_NAMES[method]
+      if headers[format_header].present? || req.headers[format_header].blank?
+        headers == req.headers
+      else
+        headers.dup.merge(format_header => req.headers[format_header]) == req.headers
+      end
+    end
   end
 
   class Response