public static void TestNoNegativeSales()
    {
        SalesCalculator calculator = new SalesCalculator();

        for (int i = 0; i < 1000; i++)
        {
            calculator.Quality            = Random.Range(0f, 1f);
            calculator.PriceOfProduct     = Random.Range(0f, 100f);
            calculator.PriceInvested      = Random.Range(0f, 100000f);
            calculator.MagnitudeOfQuality = Random.Range(0f, 10f);
            int day = Random.Range(0, 100);

            float result = calculator.CopiesSoldByDayX(day);

            Debug.Assert(result >= 0, "Calculor calculated negative sales for " + calculator.ToString() + " at day " + day + " Value: " + result);
            if (result < 0)
            {
                return;
            }
        }
    }