code: public function expectOnce($method, $args = false, $message = '%s')
      {
          $this->expectCallCount($method, 1, $message);
          if ($args !== false) {
              $this->expect($method, $args, $message);
          }
      }
docs: Convenience method for a single method call.
  
  @param string $method     Method call to track.
  @param array $args        Expected argument list or false for any arguments.
  @param string $message    Overridden message.