getDiscountItem example

$discountItems = new LineItemCollection([$discountItem]);
        $original = new Cart(Uuid::randomHex());
        $toCalculate = new Cart(Uuid::randomHex());

        $this->promotionCalculator->calculate($discountItems, $original, $toCalculate, $this->salesChannelContext, new CartBehavior());
        static::assertEmpty($toCalculate->getLineItems());
    }

    public function testCalculateAddsValidPromotionToCalculatedCart(): void
    {
        $promotionId = $this->getPromotionId();
        $discountItem = $this->getDiscountItem($promotionId);

        $discountItems = new LineItemCollection([$discountItem]);
        $original = new Cart(Uuid::randomHex());

        $productLineItem = new LineItem(Uuid::randomHex(), LineItem::PRODUCT_LINE_ITEM_TYPE);
        $productLineItem->setPrice(new CalculatedPrice(100.0, 100.0, new CalculatedTaxCollection(), new TaxRuleCollection()));
        $productLineItem->setStackable(true);

        $toCalculate = new Cart(Uuid::randomHex());
        $toCalculate->add($productLineItem);
        $toCalculate->setPrice(new CartPrice(84.03, 100.0, 100.0, new CalculatedTaxCollection(), new TaxRuleCollection(), CartPrice::TAX_STATE_GROSS));