module Mocha::IgnoringWarning

def ignoring_warning(pattern, if_: true)
  return yield unless if_
  begin
    original_warn = Warning.method(:warn)
    Warning.singleton_class.define_method(:warn) do |message|
      original_warn.call(message) unless message =~ pattern
    end
    yield
  ensure
    Warning.singleton_class.undef_method(:warn)
    Warning.singleton_class.define_method(:warn, original_warn)
  end
end