# File lib/rspec/matchers/built_in/yield.rb, line 34
        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