class RSpec::Matchers::BuiltIn::YieldProbe

def yielded_once?(matcher_name)
  case num_yields
  when 1 then true
  when 0 then false
  else
    raise "The #{matcher_name} matcher is not designed to be used with a " \
          'method that yields multiple times. Use the yield_successive_args ' \
          'matcher for that case.'
  end
end