module ActionDispatch::Assertions::ResponseAssertions

assert_response 401
# assert that the response code was status code 401 (unauthorized)

assert_response :redirect
# assert that the response was a redirection

See Rack::Utils::SYMBOL_TO_STATUS_CODE for a full list.
or its symbolic equivalent assert_response(:not_implemented).
You can also pass an explicit status number like assert_response(501)

* :error - Status code was in the 500-599 range
* :missing - Status code was 404
* :redirect - Status code was in the 300-399 range
* :success - Status code was in the 200-299 range

Asserts that the response is one of the following types:

def assert_response(type, message = nil)
  message ||= "Expected response to be a <#{type}>, but was <#{@response.response_code}>"
  if Symbol === type
    if [:success, :missing, :redirect, :error].include?(type)
      assert @response.send("#{type}?"), message
    else
      code = Rack::Utils::SYMBOL_TO_STATUS_CODE[type]
      assert_equal code, @response.response_code, message
    end
  else
    assert_equal type, @response.response_code, message
  end
end