lib/Promise/ReturnPromise.php
public function execute(array $args, FunctionProphecy $function)
    {
        $value = array_shift($this->returnValues);

        if (!count($this->returnValues)) {
            $this->returnValues[] = $value;
        }

        return $value;
    }
public function execute(array $args, FunctionProphecy $function)
    {
        $value = array_shift($this->returnValues);

        if (!count($this->returnValues)) {
            $this->returnValues[] = $value;
        }

        return $value;
    }
Returns saved values one by one until last one, then continuously returns last value.

@param array          $args
@param FunctionProphecy $function

@return mixed