public void CalculateCosts_Given3500KWhInOneYear_Returns830()
        {
            BasicTariffCostsCalculation calculationUnderTest = CreateCalculation();
            double actual = calculationUnderTest.CalculateCosts(periodInMonths: 12, consumptionInKWh: 3500);

            Assert.Equal(830, actual);
        }
        public void CalculateCosts_Given0Months_ReturnsZero()
        {
            BasicTariffCostsCalculation calculationUnderTest = CreateCalculation();
            double actual = calculationUnderTest.CalculateCosts(periodInMonths: 0, consumptionInKWh: 0);

            Assert.Equal(0, actual);
        }
        public void CalculateCosts_Given0KWhInOneYear_ReturnsAnnualBaseCosts()
        {
            BasicTariffCostsCalculation calculationUnderTest = CreateCalculation();
            double actual = calculationUnderTest.CalculateCosts(periodInMonths: 12, consumptionInKWh: 0);

            Assert.Equal(12 * calculationUnderTest.BaseCostsPerMonth, actual);
        }
        public void CalculateCosts_GivenNegativeConsumption_Throws()
        {
            BasicTariffCostsCalculation calculationUnderTest = CreateCalculation();

            Assert.ThrowsAny <ArgumentException>(() => calculationUnderTest.CalculateCosts(periodInMonths: 0, consumptionInKWh: -1));
        }