public void RepaymantServieThrowsRepaymantCalculationExceptionCase1()
{
/*
Given the following inputs:
Loan amount = 290000
Annual Interest rate = 7.5 (note this is the annual interest rate and we require a monthly repayment figure)
Term years = 0
Term months = 0
This should cause an error to occur in the calculation which must be trapped and displayed to the user in a friendly manner
*/
try
{
Repayment paymentTest = new Repayment() { AnnualInterestRate = 7.5, LoanAmount = 290000, TermMonths = 0, TermYears = 0 };
var monthlyPaymant = paymentService.MonthlyPaymentAmount(paymentTest);
var totalToBePaid = paymentService.AmountPaidBack(paymentTest);
}
catch (Exception e)
{
int? c = null;
if (e is RepaymantCalculationException) c = (e as RepaymantCalculationException).code;
Assert.That(c, Is.EqualTo(100));
}
}
// Total amount pay back when the completion of total repaymants
public double AmountPaidBack(Repayment payment)
{
if (payment.TermMonths <= 0 && payment.TermYears <= 0)
{
throw new RepaymantCalculationException("Minimum Repaymant term should be one month or more", ExceptionCode.REPAYMENT_TERM_EQUALS_TO_0);
}
var repaymentMonths = (payment.TermYears * 12) + payment.TermMonths;
return Math.Round((MonthlyPaymentAmount(payment) * repaymentMonths), 2, MidpointRounding.AwayFromZero);
}
public void RepaymantServieTestCase1()
{
/* Loan amount = 145000
Annual Interest rate = 4.5 (note this is the annual interest rate and we require a monthly repayment figure)
Term years = 23
Term months = 7
The resulting monthly repayment = 832.33
Total to be repaid = 235549.39 */
Repayment paymentTest = new Repayment() { AnnualInterestRate = 4.5, LoanAmount = 145000, TermMonths = 7, TermYears =23 };
var monthlyPaymant = paymentService.MonthlyPaymentAmount(paymentTest);
var totalToBePaid = paymentService.AmountPaidBack(paymentTest);
Assert.That(monthlyPaymant, Is.EqualTo(832.33));
Assert.That(totalToBePaid, Is.EqualTo(235549.39));
}
public RepaymantViewModel getRepaymentData(RepaymantViewModel model)
{
try
{
// We can use Automapper to Map View Model to Model
var paymant = new Repayment() { LoanAmount = model.LoanAmount, AnnualInterestRate = model.AnnualInterestRate, TermYears = model.TermYears, TermMonths = model.TermMonths };
model.MonthlyRepaymant = paymentService.MonthlyPaymentAmount(paymant);
model.TotalToBePaid = paymentService.AmountPaidBack(paymant);
return model;
}
catch (Exception e)
{
throw new HttpResponseException(Request.CreateResponse(
HttpStatusCode.NotAcceptable, new ErrorResponseView(e).message));
}
}
// get Payment amount
// The formula for calculating the monthly payment amount is in WIKI
// https://en.wikipedia.org/wiki/Mortgage_calculator
public double MonthlyPaymentAmount(Repayment payment)
{
if (payment.TermMonths <= 0 && payment.TermYears <= 0)
{
throw new RepaymantCalculationException("Minimum Repaymant term should be one month or more", ExceptionCode.REPAYMENT_TERM_EQUALS_TO_0);
}
try
{
var repaymentMonths = (payment.TermYears * 12) + payment.TermMonths;
double rate = payment.AnnualInterestRate / 100 / 12;
double denaminator = Math.Pow((1 + rate), repaymentMonths) - 1;
return Math.Round((rate + (rate / denaminator)) * payment.LoanAmount, 2, MidpointRounding.AwayFromZero);
}
catch (Exception e)
{
throw new RepaymantCalculationException(e.Message, ExceptionCode.UN_HANDLED);
}
}
public void RepaymantServieTestCase2()
{
/*
Given the following inputs:
Loan amount = 290000
Annual Interest rate = 7.5 (note this is the annual interest rate and we require a monthly repayment figure)
Term years = 15
Term months = 6
The resulting monthly repayment = 2641.50
Total to be repaid = 491319.00
*/
Repayment paymentTest = new Repayment() { AnnualInterestRate = 7.5, LoanAmount = 290000, TermMonths = 6, TermYears = 15 };
var monthlyPaymant = paymentService.MonthlyPaymentAmount(paymentTest);
var totalToBePaid = paymentService.AmountPaidBack(paymentTest);
Assert.That(monthlyPaymant, Is.EqualTo(2641.50));
Assert.That(totalToBePaid, Is.EqualTo(491319.00));
}
