class RSpec::Rails::Railtie

def supports_action_mailer_previews?(config)
  # These checks avoid loading `ActionMailer`. Using `defined?` has the
  # side-effect of the class getting loaded if it is available. This is
  # problematic because loading `ActionMailer::Base` will cause it to
  # read the config settings; this is the only time the config is read.
  # If the config is loaded now, any settings declared in a config block
  # in an initializer will be ignored.
  #
  # If the action mailer railtie has not been loaded then `config` will
  # not respond to the method. However, we cannot use
  # `config.action_mailer.respond_to?(:preview_path)` here as it will
  # always return `true`.
  config.respond_to?(:action_mailer)
end