Clean up test output

From: https://github.com/omniauth/omniauth-saml/blob/master/spec/spec_helper.rb

Author: fbacall

spec/spec_helper.rb

@@ -7,6 +7,8 @@
 require 'omniauth'
 require 'omniauth-ldap'
 
+TEST_LOGGER = Logger.new(StringIO.new)
+OmniAuth.config.logger = TEST_LOGGER
 OmniAuth.config.request_validation_phase = proc {}
 
 RSpec.configure do |config|