Setup test environment.
`rake test` to run.
Use stripped version of test_helper.
Install test-unit gem because Ruby 2.0 only have
minutest.
Follow standard interface and consume raw_post
instead of params from Rails.
父類別與其他實作都是接受 raw_post，所以遵循此介面。
父類別也有定義 params 變數跟其 parse 實作，可直接使用。
Rename form attribute mapping to use common names
Remove duplicate methods that are already defined
by mapping() calls.