public void TestNpv()
{
double r, npv, x;
r = 1;
double[] v = new double[] { 100, 200, 300, 400 };
npv = FinanceLib.npv(r, v);
x = 162.5;
Assert.AreEqual(x, npv, 0.000001);
r = 2.5; v = new double[] { 1000, 666.66666, 333.33, 12.2768416 };
npv = FinanceLib.npv(r, v);
x = 347.99232604144827;
Assert.AreEqual(x, npv, 0.000001);
r = 12.33333; v = new double[] { 1000, 0, -900, -7777.5765 };
npv = FinanceLib.npv(r, v);
x = 74.3742433377061;
Assert.AreEqual(x, npv, 0.000001);
r = 0.05; v = new double[] { 200000, 300000.55, 400000, 1000000, 6000000, 7000000, -300000 };
npv = FinanceLib.npv(r, v);
x = 11342283.4233124;
Assert.AreEqual(x, npv, 0.0000001);
}
public void TestNper()
{
double f, r, y, p, x, n;
bool t = false;
r = 0; y = 7; p = 2; f = 3; t = false;
n = FinanceLib.nper(r, y, p, f, t);
x = -0.71428571429; // can you believe it? excel returns nper as a fraction!??
Assert.AreEqual(x, n, 0.0000000001);
// cross check with pv
r = 1; y = 100; p = -109.66796875; f = 10000; t = false;
n = FinanceLib.nper(r, y, p, f, t);
x = 10;
Assert.AreEqual(x, n, 0.01);
r = 1; y = 100; p = -209.5703125; f = 10000; t = true;
n = FinanceLib.nper(r, y, p, f, t);
x = 10;
Assert.AreEqual(x, n, 0.1);
// cross check with fv
r = 2; y = 120; f = -6409178400d; p = 12000; t = false;
n = FinanceLib.nper(r, y, p, f, t);
x = 12;
Assert.AreEqual(x, n, "nper ");
r = 2; y = 120; f = -6472951200d; p = 12000; t = true;
n = FinanceLib.nper(r, y, p, f, t);
x = 12;
Assert.AreEqual(x, n, "nper ");
}
public void TestPmt()
{
double f, r, y, p, x;
int n;
bool t = false;
r = 0; n = 3; p = 2; f = 7; t = true;
y = FinanceLib.pmt(r, n, p, f, t);
x = -3;
Assert.AreEqual(x, y, "pmt ");
// cross check with pv
r = 1; n = 10; p = -109.66796875; f = 10000; t = false;
y = FinanceLib.pmt(r, n, p, f, t);
x = 100;
Assert.AreEqual(x, y, "pmt ");
r = 1; n = 10; p = -209.5703125; f = 10000; t = true;
y = FinanceLib.pmt(r, n, p, f, t);
x = 100;
Assert.AreEqual(x, y, "pmt ");
// cross check with fv
r = 2; n = 12; f = -6409178400d; p = 12000; t = false;
y = FinanceLib.pmt(r, n, p, f, t);
x = 120;
Assert.AreEqual(x, y, "pmt ");
r = 2; n = 12; f = -6472951200d; p = 12000; t = true;
y = FinanceLib.pmt(r, n, p, f, t);
x = 120;
Assert.AreEqual(x, y, "pmt ");
}
public void GetPresentValue_Should_Throw_ArgumentOutOfRangeException_When_Interest_Rate_Less_Than_Zero()
{
//Arrange
double repayment = 10000;
double interestRate = -4.8;
int loanTerm = 3;
FinanceLib sut = new FinanceLib();
//Assert
Assert.Throws <ArgumentOutOfRangeException>(() => { sut.GetPresentValue(repayment, interestRate, loanTerm); });
}
public void GetRepayment_Should_Throw_ArgumentOutOfRangeException_When_Loan_Term_Less_Than_Zero()
{
//Arrange
double loanAmount = 10000;
double interestRate = 4.8;
int loanTerm = -3;
FinanceLib sut = new FinanceLib();
//Assert
Assert.Throws <ArgumentOutOfRangeException>(() => { sut.GetRepayment(loanAmount, interestRate, loanTerm); });
}
public void Should_Return_Present_Value_Of_Loan()
{
//Arrange
double repayment = 250;
double interestRate = 4.8;
int loanTerm = 3;
double expectedResult = 8366.47;
FinanceLib sut = new FinanceLib();
//Act
double actualResult = sut.GetPresentValue(repayment, interestRate, loanTerm);
//Assert
Assert.Equal(expectedResult, Math.Round(actualResult, 2));
}
public void Should_Return_Monthly_Repayment()
{
//Arrange
double loanAmount = 10000;
double interestRate = 4.8;
int loanTerm = 3;
double expectedResult = 298.81;
FinanceLib sut = new FinanceLib();
//Act
double actualResult = sut.GetRepayment(loanAmount, interestRate, loanTerm);
//Assert
Assert.Equal(expectedResult, Math.Round(actualResult, 2));
}
public void TestFv()
{
double f, r, y, p, x;
int n;
bool t = false;
r = 0; n = 3; y = 2; p = 7; t = true;
f = FinanceLib.fv(r, n, y, p, t);
x = -13;
Assert.AreEqual(x, f, "fv ");
r = 1; n = 10; y = 100; p = 10000; t = false;
f = FinanceLib.fv(r, n, y, p, t);
x = -10342300;
Assert.AreEqual(x, f, "fv ");
r = 1; n = 10; y = 100; p = 10000; t = true;
f = FinanceLib.fv(r, n, y, p, t);
x = -10444600;
Assert.AreEqual(x, f, "fv ");
r = 2; n = 12; y = 120; p = 12000; t = false;
f = FinanceLib.fv(r, n, y, p, t);
x = -6409178400d;
Assert.AreEqual(x, f, "fv ");
r = 2; n = 12; y = 120; p = 12000; t = true;
f = FinanceLib.fv(r, n, y, p, t);
x = -6472951200d;
Assert.AreEqual(x, f, "fv ");
// cross tests with pv
r = 2.95; n = 13; y = 13000; p = -4406.78544294496; t = false;
f = FinanceLib.fv(r, n, y, p, t);
x = 333891.230010986; // as returned by excel
Assert.AreEqual(x, f, 0.01);
r = 2.95; n = 13; y = 13000; p = -17406.7852148156; t = true;
f = FinanceLib.fv(r, n, y, p, t);
x = 333891.230102539; // as returned by excel
Assert.AreEqual(x, f, 0.01);
}
public void TestPv()
{
double f, r, y, p, x;
int n;
bool t = false;
r = 0; n = 3; y = 2; f = 7; t = true;
f = FinanceLib.pv(r, n, y, f, t);
x = -13;
Assert.AreEqual(x, f, "pv ");
r = 1; n = 10; y = 100; f = 10000; t = false;
p = FinanceLib.pv(r, n, y, f, t);
x = -109.66796875;
Assert.AreEqual(x, p, "pv ");
r = 1; n = 10; y = 100; f = 10000; t = true;
p = FinanceLib.pv(r, n, y, f, t);
x = -209.5703125;
Assert.AreEqual(x, p, "pv ");
r = 2.95; n = 13; y = 13000; f = 333891.23; t = false;
p = FinanceLib.pv(r, n, y, f, t);
x = -4406.78544294496;
Assert.AreEqual(x, p, 0.0000001);
r = 2.95; n = 13; y = 13000; f = 333891.23; t = true;
p = FinanceLib.pv(r, n, y, f, t);
x = -17406.7852148156;
Assert.AreEqual(x, p, 0.0000001);
// cross tests with fv
r = 2; n = 12; y = 120; f = -6409178400d; t = false;
p = FinanceLib.pv(r, n, y, f, t);
x = 12000;
Assert.AreEqual(x, p, "pv ");
r = 2; n = 12; y = 120; f = -6472951200d; t = true;
p = FinanceLib.pv(r, n, y, f, t);
x = 12000;
Assert.AreEqual(x, p, "pv ");
}
public override double Evaluate(double rate, double arg1, double arg2, double arg3, bool type)
{
return(FinanceLib.pv(rate, arg1, arg2, arg3, type));
}
static void Main(string[] args)
{
string choice = "";
do
{
//Get menu choice
ShowMenu();
choice = Console.ReadLine();
//calculate monthly repayment
if (choice == "1")
{
double loanAmount;
do
{
Console.WriteLine("Enter the loan amount in dollars (e.g. 10000):");
} while (!Double.TryParse(Console.ReadLine(), out loanAmount) || loanAmount <= 0);
double interestRate;
do
{
Console.WriteLine("Enter interest rate as a percentage (e.g. 5.2):");
} while (!Double.TryParse(Console.ReadLine(), out interestRate) || interestRate <= 0);
int loanTermInYears;
do
{
Console.WriteLine("Enter the term of the loan in years (e.g. 5):");
} while (!Int32.TryParse(Console.ReadLine(), out loanTermInYears) || loanTermInYears <= 0);
//create new calculator object to call repayment method
//Note: This could also be made into a static class if little domain logic is required
FinanceLib calculator = new FinanceLib();
try
{
double monthlyRepayment = calculator.GetRepayment(loanAmount, interestRate, loanTermInYears);
Console.WriteLine($"Monthly Repayments: ${Math.Round(monthlyRepayment,2)}");
Console.WriteLine();
//Append details of loan calculation to loans.txt file
//This file is in the bin folder so will be removed if a clean of the project is performed. For a real system this data
//would be persisted in a proper data store
using (StreamWriter writer = new StreamWriter("loans.txt", true))
{
writer.WriteLine(calculator);
}
}
//probably never hit as UI does some valdiation
catch (ArgumentOutOfRangeException ex)
{
Console.WriteLine(ex.Message);
Console.WriteLine();
}
}
//Present Value calculation
else if (choice == "2")
{
double repayment;
//get input and validate
do
{
Console.WriteLine("Enter the monthly repayment amount in dollars (e.g. 250):");
} while (!Double.TryParse(Console.ReadLine(), out repayment) || repayment <= 0);
double interestRate;
do
{
Console.WriteLine("Enter interest rate as a percentage (e.g. 5.2):");
} while (!Double.TryParse(Console.ReadLine(), out interestRate) || interestRate <= 0);
int loanTermInYears;
do
{
Console.WriteLine("Enter the term of the loan in years (e.g. 5):");
} while (!Int32.TryParse(Console.ReadLine(), out loanTermInYears) || loanTermInYears <= 0);
//create new calculator object to call repayment method
//Note: This could also be made into a static class if little domain logic is required
FinanceLib calculator = new FinanceLib();
try
{
double presentValue = calculator.GetPresentValue(repayment, interestRate, loanTermInYears);
Console.WriteLine($"Present Value of the loan: ${Math.Round(presentValue, 2)}");
Console.WriteLine();
//Append details of loan calculation to loans.txt file
//This file is in the bin folder so will be removed if a clean of the project is performed. For a real system this data
//would be persisted in a proper data store
using (StreamWriter writer = new StreamWriter("loans.txt", true))
{
writer.WriteLine(calculator);
}
}
//probably never hit as UI does some valdiation
catch (ArgumentOutOfRangeException ex)
{
Console.WriteLine(ex.Message);
Console.WriteLine();
}
}
//display calculations saved to file
else if (choice == "3")
{
try
{ // Open the text file using a stream reader.
using (StreamReader sr = new StreamReader("loans.txt"))
{
// Read the stream to a string, and write the string to the console.
String line = sr.ReadToEnd();
Console.WriteLine(line);
}
}
catch (Exception e)
{
Console.WriteLine("The file could not be read:");
Console.WriteLine(e.Message);
}
}
}while (choice != "4");
Console.WriteLine("Exiting program...");
}
