public double GetAmountOwed(Trip trip)
{
var expenses = trip.Expenses;
if (expenses.Any(x => x < 0))
{
throw new ArgumentException("At least one of the expense values is invalid.");
}
var tripCost = expenses.Sum();
var costPerPayer = tripCost / expenses.Count;
double owedTotal = 0;
foreach(var expense in expenses)
{
var difference = costPerPayer - expense;
if(difference > 0)
{
owedTotal = owedTotal + difference;
}
}
return Math.Truncate(owedTotal * 100) / 100;
}
public void HappyPathZeroesInDecimalPlaces()
{
var trip = new Trip { Expenses = new List<double> { 10, 20, 30 } };
var retval = expenseCalculator.GetAmountOwed(trip);
Assert.AreEqual(10, retval);
}
public void NegativeExpenseValueThrowsException()
{
var trip = new Trip { Expenses = new List<double> { -15.01, 15, 3, 3.01 } };
Assert.Throws<ArgumentException>(() => expenseCalculator.GetAmountOwed(trip));
}
public void HappyPathValuesInDecimalPlaces()
{
var trip = new Trip { Expenses = new List<double> { 15.01, 15, 3, 3.01 } };
var retval = expenseCalculator.GetAmountOwed(trip);
Assert.AreEqual(11.99, retval);
}