1. JUnit
ksa-in project study

2. 배경 지식

3. JUnit 이란?

4. JUnit 이란?
Unit testing framework for Java

5. Test Phases
• Unit testing on individual units of source
code (= smallest testable part)
• Integration testing on groups of
individual software modules
• System testing on a
complete, integrated system (evaluate
compliance with requirements)

6. TDD(Test Driven Development)
• Software Development Process
– Family of Agile
• Test code를 작성하는 것이 소프트웨어 개
발의 시작!
• Automated Test

7. TDD Process
Refactor
Add a test
code
Run all
Run the
tests and
tests and
see if the
see them
new one
succeed
fails
Write some
code

8. Junit 4 뭐가 달라졌나?
import static com.wakaleo.gameoflife.domain.Cell.DEAD_CELL;
import static com.wakaleo.gameoflife.domain.Cell.LIVE_CELL;
import static org.hamcrest.MatcherAssert.assertThat;
import static org.hamcrest.Matchers.is;
No need to extend TestCase
import org.junit.Test;
public class WhenYouCreateACell {
Annotation based
@Test
public void aLiveCellShouldBeRepresentedByAnAsterisk() {
Cell cell = Cell.fromSymbol("*");
assertThat(cell, is(LIVE_CELL));
} Call the tests anything you want
@Ignore("Pending Implementation") Annotations for test metadata
@Test
public void aDeadCellShouldBeRepresentedByADot() {
Cell cell = Cell.fromSymbol(".");
assertThat(cell, is(DEAD_CELL));
}
...
}

9. 일단 시작해봅시다!

10. 간단한 test

11. 간단한 test

12. 고쳐보자

13. 성공?

14. 좀 더 복잡한 테스트

15. 제대로 고치면 성공!

16. 일단 Test는 짰는데 구현하기는 어렵고…
Test 할 때마다 빨간 막대기 보기 싫고…

17. @Before & @After
• @Before는 해당 클래스의 각각의 test가 실행되기 전에 동작(setup)
• @After는 해당 클래스의 각각의 test가 실행된 이후에 동작(tear
down)
• @Before
public void runBeforeEveryTest() {
simpleMath = new SimpleMath();
}
• @After
public void runAfterEveryTest() {
simpleMath = null;
}

18. @BeforeClass & @AfterClass
• @BeforeClass는 해당 클래스의 test들이 시작되기 전 한 번 동작
(setup)
• @AfterClass는 해당 클래스의 test가 모두 실행된 이후에 동작(tear
down)
• @BeforeClass
public static void runBeforeClass() {
// run for one time before all test cases
}
• @AfterClass
public static void runAfterClass() {
// run for one time after all test cases
}

19. Exception Handling
• @Test(expected = <Exception 종류>
• 해당 Exception이 나야 test를 통과, Exception이 나지 않고 테스트가
끝나면 fail
• @Test(expected = ArithmeticException.class)
public void divisionWithException() {
// divide by zero
simpleMath.divide(1, 0);
}

20. Timeout
• @Test(timeout = <시간, ms단위>)
• 해당 시간 내에 test가 끝나지 않으면 fail
• @Test(timeout = 1000)
public void infinity() {
while (true)
;
}

21. 유닛 테스트가 좋은건 알겠는데…
모든 메소드를 테스트 해야되나?

22. 유닛 테스트가 좋은건 알겠는데…
모든 메소드를 테스트 해야되나?
GET, SET 메소드도?

23. 모범 답안
• Code를 쓰기 전에 Test를 씁시다
• 뭔가 깨질 껀덕지가 보이면 Test를 합시다.
• get, set 메소드처럼 깨지기엔 너무 간단한
(too simple to break) 애들은 하지 말고요.
• Test code를 짰으면 자주 실행시킵시다.

24. Test Double
• Dummy objects are passed around but never actually used. Usually
they are just used to fill parameter lists.
• Fake objects actually have working implementations, but usually
take some shortcut which makes them not suitable for production
(an in memory database is a good example).
• Stubs provide canned answers to calls made during the test, usually
not responding at all to anything outside what's programmed in for
the test. Stubs may also record information about calls, such as an
email gateway stub that remembers the messages it 'sent', or
maybe only how many messages it 'sent'.
• Mocks are objects pre-programmed with expectations which form a
specification of the calls they are expected to receive.

25. Stub(1/2)
• public interface MailService {
public void send (Message msg);
}
public class MailServiceStub implements MailService {
private List<Message> messages = new ArrayList<Message>();
public void send (Message msg) {
messages.add(msg);
}
public int numberSent() {
return messages.size();
}
}

26. Stub(2/2)
• class OrderStateTester...
public void testOrderSendsMailIfUnfilled() {
Order order = new Order(TALISKER, 51);
MailServiceStub mailer = new MailServiceStub();
order.setMailer(mailer);
order.fill(warehouse);
assertEquals(1, mailer.numberSent());
}

27. Mock
• class OrderInteractionTester...
public void testOrderSendsMailIfUnfilled() {
Order order = new Order(TALISKER, 51);
Mock warehouse = mock(Warehouse.class);
Mock mailer = mock(MailService.class);
order.setMailer((MailService) mailer.proxy());
mailer.expects(once()).method("send");
warehouse.expects(once()).method("hasInventory")
.withAnyArguments()
.will(returnValue(false));
order.fill((Warehouse) warehouse.proxy());
}
}

28. Reference
• Unit testing with JUnit
– http://www.slideshare.net/tom.zimmermann/unit-
testing-with-junit
• JUnit 4 in 60 seconds
– http://www.cavdar.net/2008/07/21/junit-4-in-60-
seconds/
• Mocks aren’t stubs
– http://martinfowler.com/articles/mocksArentStubs.
html#TheDifferenceBetweenMocksAndStubs