public void ShouldThroughArgumentException(double consumption)
        {
            // Arrange
            var basicTariff = new BasicTariff();

            // Act
            // Assert
            Assert.Throws <ArgumentException>(() => basicTariff.GetAnnualCosts(consumption), "Should throw ArgumentException when consumption less 0");
        }
        public void ShouldReturnValidAnnualCosts(int consumption, int cost)
        {
            // Arrange
            var basicTariff = new BasicTariff();

            // Act
            var annualCosts = basicTariff.GetAnnualCosts(consumption);

            // Assert
            Assert.AreEqual(cost, annualCosts, "Annual cost calculated incorrectly");
        }