public void GivenCustomerWhenCustomerIsPresentThenReturnAverageMonthlyPremium()
{
// Arrange
var mockPremiumCalculator = new Mock <IPremiumCalculator>();
mockPremiumCalculator.Setup(c => c.CalculateAverageMonthlyPremium(It.IsAny <decimal>(), It.IsAny <int>())).Returns(4.375M);
var mockCustomer = this.GetCustomerMock();
var premiumCalculatorBuilder = new CustomerBuilder(mockPremiumCalculator.Object);
premiumCalculatorBuilder.Set(mockCustomer);
// Act
premiumCalculatorBuilder.CalculateAverageMonthlyPremium();
// Assert
mockPremiumCalculator.Verify(c => c.CalculateAverageMonthlyPremium(It.IsAny <decimal>(), It.IsAny <int>()), Times.Once);
Assert.AreEqual(4.375M, mockCustomer.AverageMonthlyPremium);
}