LoanTest.java

package mytest;

import org.junit.*;
import static org.junit.Assert.*;

public class LoanTest {
  @Before
  public void setUp() throws Exception {
  }
  
  @Test
  public void testPaymentMethods() {
    double annualInterestRate = 2.5;
    int numberOfYears = 5;
    double loanAmount = 1000;
    Loan loan = new Loan(annualInterestRate, numberOfYears,
    loanAmount);
    assertTrue(loan.getMonthlyPayment() ==
    getMonthlyPayment(annualInterestRate, numberOfYears,
    loanAmount));
    assertTrue(loan.getTotalPayment() ==
    getTotalPayment(annualInterestRate, numberOfYears,
    loanAmount));
  }
  
  /** Find monthly payment */
  private double getMonthlyPayment(double annualInterestRate,
  int numberOfYears, double loanAmount) {
  double monthlyInterestRate = annualInterestRate / 1200;
  double monthlyPayment = loanAmount * monthlyInterestRate / (1 -
  (1 / Math.pow(1 + monthlyInterestRate, numberOfYears * 12)));
  return monthlyPayment;
  }
  
  /** Find total payment */
  public double getTotalPayment(double annualInterestRate,
  int numberOfYears, double loanAmount) {
  return getMonthlyPayment(annualInterestRate, numberOfYears,
  loanAmount) * numberOfYears * 12;
  }
}