def method_missing msg, *args, &block
      defi = Definition.new(msg, args, block)
      if injected = __mock_injected[defi.msg]
        defi.original_method = injected.original_method
      else
        __mock_inject_method(defi)
      end
      __mock_defis_push(defi)
      Modifier.new(self, defi)
    end
def method_missing msg, *args, &block
      defi = Definition.new(msg, args, block)
      if injected = __mock_injected[defi.msg]
        defi.original_method = injected.original_method
      else
        __mock_inject_method(defi)
      end
      __mock_defis_push(defi)
      Modifier.new(self, defi)
    end
Public API: Define mocked method