Silence specific deprecation warnings in Rails 3+

Sometimes you're getting an ActiveSupport deprecation warning that you cannot or don't want to fix. In these cases, it might be okay to silence some specific warnings. Add this to your initializers, or require it in your tests:

silenced = [
  /Not considered a useful test/,
  /use: should(_not)? have_sent_email/,
] # list of warnings you want to silence

silenced_expr = Regexp.new(silenced.join('|'))

ActiveSupport::Deprecation.behavior = lambda do |msg, stack|
  unless msg =~ silenced_expr
    ActiveSupport::Deprecation::DEFAULT_BEHAVIORS[:stderr].call(msg, stack)
  end
end

This will only work with warnings that go through ActiveSupport and only in Rails 3.0 or higher.