public void GivenCustomerWhenCustomerIsPresentThenReturnCreditCharge()
{
// Arrange
var mockPremiumCalculator = new Mock <IPremiumCalculator>();
mockPremiumCalculator.Setup(c => c.CalculateCreditCharge(It.IsAny <decimal>())).Returns(2.5M);
var mockCustomer = this.GetCustomerMock();
var premiumCalculatorBuilder = new CustomerBuilder(mockPremiumCalculator.Object);
premiumCalculatorBuilder.Set(mockCustomer);
// Act
premiumCalculatorBuilder.CalculateCreditCharge();
// Assert
mockPremiumCalculator.Verify(c => c.CalculateCreditCharge(It.IsAny <decimal>()), Times.Once);
Assert.AreEqual(2.5M, mockCustomer.CreditCharge);
}