1. Unit Testing Yonglei Tao

2. Test-First Development • Essential element in eXtreme Programming (XP) • Test is written before the code • Developers have to understand the specification thoroughly

3. A Simple Way for Unit Testing class Point { int x, y; Point () { x = O; y = O; } Point ( int x, int y ) { this.x = x; this.y = y; } public String toString () { return ( "( " + x + ", " + y + " )" ); } public static void main(String[] args) { Point p1 = new Point(); System.out.println("(0,0)=“ + p1); Point p2 = new Point(3,5); System.out.println("(3,5)=" + p2); } }

4. JUnit • A free framework for unit testing • Written by Kent Beck & Erich Gamma • Available at: http://www.junit.org/ • Helps create and run individual and groups of test cases • Allows test cases to be self-checked • Test cases are reusable • Run test cases whenever changes are made • Programmers become much less reluctant to improvetheir code since they can easily validate their changes

5. An Example Class class Money {     private int amount;     private String currency;    public Money(int amt, String cur) {         amount= amt;         currency= cur;     }     public double getAmount() { return amount; } public String getCurrency() { return currency; } public Money add(Money m) {     return new Money(amount + m.amount, currency); } }

6. Define a Test Case public class MoneyTest {   @Test public void testConstructor() {     Money m1= new Money(12, "USD");     Money m2= new Money(14, "USD");   assertTrue ( !m1.equals(null) );     assertEquals ( m1, m1 );     assertEquals ( m1, new Money(12, "USD") );     assertTrue ( !m1.equals(m2) ); } }

7. More Test Method • Code a little, test a little, code a little, test a little @Test public void testAdd() {         Money m1= new Money(12, "USD");          Money m2= new Money(14, "USD");   Money expected= new Money(26, "USD");         Money result= m1.add(m2);            assertTrue ( expected.equals(result) );       }

8. Assert Methods • assertTrue (Boolean cond) • assertTrue (String msg, Boolean cond) • assertFalse (Boolean cond) • assertFalse (String msg, Boolean cond) • assertEquals (Object expected, Object actual) • assertEquals (double expected, double actual, double delta) • assertNull (Object obj) • assertNotNull (Object obj) • assertNotSame (Object obj1, Object obj2) • And more to search for Java Class Assert

9. Annotations public class MoneyTest {     private Money m1     private Money m2;   @Before  public void setUp() {         m1 = new Money(12, "USD");         m2 = new Money(14, "USD");     } @Ignore (“not ready yet”) public void testUndefinedMethod () { … }

10. Annotations (Cont.) @Test public void testEquals() {     assertEquals ( m1, m1 );     assertEquals ( m1, new Money(12, "USD") );     assertTrue ( !m1.equals(m2) ); } @Test public void testAdd() {     Money expected= new Money(26, "USD");     Money result= m1.add(m2);     assertTrue ( expected.equals(result) ); } @Test (expected = ArithmeticException.class) public void testMethodwithBug () { … } }

11. How to Test Class BankAccount? 1 /** 2 A bank account has a balance that can be changed by 3 deposits and withdrawals. 4 */ 5 publicclass BankAccount 6 { 7 privatedouble balance; 8 9 /** 10 Constructs a bank account with a zero balance. 11 */ 12 public BankAccount() 13 { 14 balance = 0; 15 } 16 17 /** 18 Constructs a bank account with a given balance. 19 @param initialBalance the initial balance 20 */ 21 public BankAccount(double initialBalance) 22 { 23 balance = initialBalance; 24 }

12. 26 /** 27 Deposits money into the bank account. 28 @param amount the amount to deposit 29 */ 30 publicvoid deposit(double amount) 31 { 32 balance = balance + amount; 33 } 34 35 /** 36 Withdraws money from the bank account. 37 @param amount the amount to withdraw 38 */ 39 publicvoid withdraw(double amount) 40 { 41 balance = balance - amount; 42 } 43 44 /** 45 Gets the current balance of the bank account. 46 @return the current balance 47 */ 48 publicdouble getBalance() 49 { 50 return balance; 51 } 52 }