def valid_credentials?
      location = self.class.default_location
      find_rates(location,location,Package.new(100, [5,15,30]), :test => test_mode)
    rescue Omniship::ResponseError
      false
    else
      true
    end
def valid_credentials?
      location = self.class.default_location
      find_rates(location,location,Package.new(100, [5,15,30]), :test => test_mode)
    rescue Omniship::ResponseError
      false
    else
      true
    end
Validate credentials with a call to the API. By default this just does a find_rates call
 with the orgin and destination both as the carrier's default_location. Override to provide
 alternate functionality, such as checking for test_mode to use test servers, etc.