QuantityItem example

    public static function calculationProvider(): \Generator
    {
        yield 'Test empty container will be removed' => [
            new ContainerItem(),
            null,
        ];

        yield 'Test container with one quantity price definition' => [
            new ContainerItem([
                new QuantityItem(20, new HighTaxes()),
            ]),
            new CalculatedPrice(20, 20, new CalculatedTaxes([19 => 3.19]), new HighTaxes()),
        ];

        yield 'Test percentage discount for one item' => [
            new ContainerItem([
                new QuantityItem(20, new HighTaxes()),
                new PercentageItem(-10),
            ]),
            new CalculatedPrice(18, 18, new CalculatedTaxes([19 => 2.87]), new HighTaxes()),
        ];