Use assert_nil instead of assert_equal.

git-svn-id: http://svn.redmine.org/redmine/trunk@16060 e93f8b46-1217-0410-a6f0-8f06a7374b81

test/unit/lib/redmine/menu_manager/mapper_test.rb

@@ -156,7 +156,7 @@ class Redmine::MenuManager::MapperTest < ActiveSupport::TestCase
     menu_mapper.push :test_overview, { :controller => 'projects', :action => 'show'}, {}
 
     item = menu_mapper.find(:nothing)
-    assert_equal nil, item
+    assert_nil item
   end
 
   def test_delete