the mechanize session must specially handle params

{:user => {:name => "Nancy"}}
now becomes
{"user[name]" => "Nancy"}

lib/webrat/mechanize/mechanize_session.rb

@@ -15,7 +15,16 @@ module Webrat
     end
 
     def post(url, data, headers_argument_not_used = nil)
-      @mechanize_page = @mechanize.post(url, data)
+      post_data = data.inject({}) do |memo, param|
+        case param.last
+        when Hash
+          param.last.each {|attribute, value| memo["#{param.first}[#{attribute}]"] = value }
+        else
+          memo[param.first] = param.last
+        end
+        memo
+      end
+      @mechanize_page = @mechanize.post(url, post_data)
     end
 
     def response_body

spec/webrat/mechanize/mechanize_session_spec.rb

@@ -12,4 +12,25 @@ describe Webrat::MechanizeSession do
       @mech.headers.should == {}
     end
   end
+  
+  describe "post" do
+    def url
+      'http://test.host/users'
+    end
+    
+    def data
+      {:user => {:first_name => 'Nancy', :last_name => 'Callahan'}}
+    end
+    
+    def flattened_data
+      {'user[first_name]' => 'Nancy', 'user[last_name]' => 'Callahan'}
+    end
+    
+    it "should flatten model post data" do
+      mechanize = mock :mechanize
+      mechanize.should_receive(:post).with(url, flattened_data)
+      
+      Webrat::MechanizeSession.new(mechanize).post(url, data)
+    end
+  end
 end