Minitest ignores assert_response() message


I’m using Rails 3.0.6 and I find that minitest (both the Ruby 1.9.2-p180
version and also the minitest 2.0.2 gem) is ignoring the message I’m
passing to assert_response():

  post :create, content:
  assert_response :success, response.body

When the assertion fails, minitest is not showing my response.body
message and is instead always showing “Expected block to return true
value.” as the message.

Thanks for your consideration.

P.S. Test::Unit 2.2.0 does not exhibit this problem.