Ok, after some research I found out that the Rails 1.2 RC1 has a bug that makes the integration tests fail.
The following is the trouble ticket which was opened 2 months ago:
#6353: Undefined method recycle! in integration test with put or delete In a simple integration test with trunk, I get: {{{ >> get ‘books/1’ => 200 >> put ‘books/1’ NoMethodError: undefined method `recycle!’ for #ActionController::CgiRequest:0x2cef98c from /Users/jasongarber/Documents/form_ test_helper/confi … By jgarber — 10/05/06 11:14:10