Ein Talk über gute und schlechte Tests in der Softwareentwicklung. Basierend auf dem Werk "Bad Tests, Good Tests" von Tomek Kaczanowski Verlag: kaczanowscy.pl Tomasz Kaczanowski (11. Dezember 2013) Sprache: Englisch ISBN-10: 8393847133 Christof Vollrate (BILD GmbH & Co. KG)

2. Dijkstra, The Humble Programmer 1972

3. Gute Tests
● Mit jedem Test stellen wir sicher, dass die getestete
Funktionalität korrekt umgesetzt ist
● Hoffnung, dass ähnliche Fälle genauso gut funktionieren
(Äquivalenzklassen)
● Änderungen werden leichter möglich, weil sichergestellt wird,
dass die bestehende Funktionalität nicht kaputt geht
● Tests sind die aktuellste Dokumentation
● Jeder Test erzählt eine Geschichte über was passiert und
was zu erwarten ist.
●

4. Böse Tests
● Fragile Tests: kleine Änderung in der
Implementierung => viele Tests betroffen
● Redundante Tests => Balast
● Triviale Tests
● Unvollständige Tests => falsche Sicherheit
● Tests ohne Asserts

5. No Assertions
IResult result = format.execute();
System.out.println(result.size());
Iterator iter = result.iterator();
while (iter.hasNext()) {
IResult r = (IResult) iter.next();
System.out.println(r.getMessage());
}

6. No Assertions
(verbessert)
IResult result = format.execute();
assertThat(result.size()).isEqualTo(3); 1
Iterator iter = result.iterator();
while (iter.hasNext()) {
IResult r = (IResult) iter.next();
assertThat(r.getMessage()).contains("error"); 2
}

7. Get- Setter
public void testSetGetParam() throws Exception {
String[] tests = {"a", "aaa", "---",
"23121313", "", null};
for (int i = 0; i < tests.length; i++) {
adapter.setParam(tests[i]);
assertEquals(tests[i], adapter.getParam());
}
}

8. Happy Path
public class FizzBuzzTest {
@Test
public void testMultipleOfThreeAndFivePrintsFizzBuzz() {
assertEquals("FizzBuzz", FizzBuzz.getResult(15));
}
@Test
public void testMultipleOfThreeOnlyPrintsFizz() {
assertEquals("Fizz", FizzBuzz.getResult(93));
}

9. Happy Path
(verbessert)
@RunWith(JUnitParamsRunner.class)
public class FizzBuzzJUnitTest {
@Test
@Parameters(value = {"15", "30", "75"})
public void testMultipleOfThreeAndFivePrintsFizzBuzz(
int multipleOf3And5) {
assertEquals("FizzBuzz", FizzBuzz.getResult(multipleOf3And5));
}
@Test
@Parameters(value = {"9", "36", "81"})
public void testMultipleOfThreeOnlyPrintsFizz(...
@Test
@Parameters(value = {"10", "55", "100"})
public void testMultipleOfFiveOnlyPrintsBuzz(...
@Test
@Parameters(value = {"2", "16", "23", "47", "52", ...
public void testInputOfEightPrintsTheNumber(...
}

10. Not Enough Testing
@Test
public class PagerTest {
private static final int PER_PAGE = 10;
public void shouldGiveOffsetZeroWhenOnZeroPage() {
Pager pager = new Pager(PER_PAGE);
assertThat(pager.getOffset()).isEqualTo(0);
}
public void shouldIncreaseOffsetWhenGoingToPageOne() {
Pager pager = new Pager(PER_PAGE);
pager.goToNextPage();
assertThat(pager.getOffset()).isEqualTo(PER_PAGE);
}
}

11. Not Enough Testing
(verbessert)
Zero, One and Many

12. Auskommentieren
//@Test
public void testTeaserWithBildPlusMarker()
{
String url = urlBuilder.setBaseUrl(HTTP_START_PATH +
TEASERREIHE_BILDPLUS_MARKER_PATH.setView("module".build();
driver.get(url);
// Teaserreihe
WebElement teaserReiheElement = getRootElement();
BTOTeaserReihe_modulePO teaserReihePO =
new BTOTeaserReihe_modulePO(teaserReiheElement);
List<Resource_teaserPO> teaserPOs =
teaserReihePO.getTeaserPOs();
assertNotNull("Teaser-Page-Objekte fehlen", teaserPOs);
assertEquals(1, teaserPOs.size());
}
(Aus bildcms JSP-Tests)

13. Auskommentieren
(verbessert)
@Test @Ignore //TODO momentan nicht testbar auf Testsystem
public void testTeaserWithBildPlusMarker()
{
String url = urlBuilder.setBaseUrl(HTTP_START_PATH +
TEASERREIHE_BILDPLUS_MARKER_PATH.setView("module".build();
driver.get(url);
// Teaserreihe
WebElement teaserReiheElement = getRootElement();
BTOTeaserReihe_modulePO teaserReihePO =
new BTOTeaserReihe_modulePO(teaserReiheElement);
List<Resource_teaserPO> teaserPOs =
teaserReihePO.getTeaserPOs();
assertNotNull("Teaser-Page-Objekte fehlen", teaserPOs);
assertEquals(1, teaserPOs.size());
}

14. Expecting Exceptions Anywhere
@Test(expected=IndexOutOfBoundsException.class)
public void testMyList() {
MyList<Integer> list = new MyList<Integer>();
list.add(1);
list.add(2);
list.add(3);
list.add(3);
list.add(4);
assertTrue(4 == list.get(4));
assertTrue(2 == list.get(1));
assertTrue(3 == list.get(2));
list.get(6);
}

15. Expecting Exceptions Anywhere
(verbessert)
● Tests aufteilen (Split)
● Exception-Test Lokalisieren

16. Assertions should be Merciless
@Test
public void shouldRemoveEmailsByState() {
//given
Email pending = createAndSaveEmail("pending","content pending",
"abc@def.com", Email.PENDING);
Email failed = createAndSaveEmail("failed","content failed",
"abc@def.com", Email.FAILED);
Email sent = createAndSaveEmail("sent","content sent",
"abc@def.com", Email.SENT);
//when
emailDAO.removeByState(Email.FAILED);
//then
assertThat(emailDAO.findAll()).excludes(failed);
}

17. Assertions should be Merciless
(verbessert)
assertThat(emailDAO.findAll(),
contains(pending, sent))

18. Is Mockito Working Fine?
@Test
public void testFormUpdate() {
// given
Form f = Mockito.mock(Form.class);
Mockito.when(
f.isUpdateAllowed()).thenReturn(true);
// when
boolean result = f.isUpdateAllowed();
// then
assertTrue(result);
}

19. @Test
public void will_getChangSecurityQuestRgtAndDetails_if_AdvUserhasRuleId25(){
User user = createUser(userId);
user.setAdvanced(true);
PasswordRuleDto passwordRuleDto = new PasswordRuleDto();
passwordRuleDto.setPasswordRuleId(rulId25);
List<PasswordRuleDto> passwordRules = new ArrayList<PasswordRuleDto>();
passwordRules.add(passwordRuleDto);
given(currentUser.getUser()).thenReturn(user);
given(userDAO.readByPrimaryKey(userId)).thenReturn(user);
given(passwordBean.getPasswordRules()).thenReturn(passwordRules);
UserSecurityQuestionDto dto = userChangeSecurityQuestionBean
.getChangSecurityQuestionRgtAndDetails();
assertNotNull(dto.getEmail());
assertNotNull(dto.getFirstName());
assertNotNull(dto.getLastName());
assertEquals(dto.isChangeSecurityQuestion(), true);
}
Why formatting helps

20. @Test
public void will_getChangSecurityQuestRgtAndDetails_if_AdvUserhasRuleId25(){
// given
User user = createUser(userId);
user.setAdvanced(true);
PasswordRuleDto passwordRuleDto = new PasswordRuleDto();
passwordRuleDto.setPasswordRuleId(rulId25);
List<PasswordRuleDto> passwordRules = new ArrayList<PasswordRuleDto>();
passwordRules.add(passwordRuleDto);
given(currentUser.getUser()).willReturn(user);
given(userDAO.readByPrimaryKey(userId)).willReturn(user);
given(passwordBean.getPasswordRules()).willReturn(passwordRules);
// when
UserSecurityQuestionDto dto = userChangeSecurityQuestionBean
.getChangSecurityQuestionRgtAndDetails();
// then
assertNotNull(dto.getEmail());
assertNotNull(dto.getFirstName());
assertNotNull(dto.getLastName());
assertEquals(dto.isChangeSecurityQuestion(), true);
}
Why formatting helps
(verbessert)

21. When a Test Name Lies
Should is Better than Test
public void testInsertNewValues() {
//given
//when
reportRepository.updateReport(ReportColumn.DATE,
ReportColumn.PLACE, reportMap(BigDecimal.TEN));
reportRepository.updateReport(ReportColumn.DATE,
ReportColumn.PLACE, reportMap(new BigDecimal("5")));
//then
assertThat(reportRepository
.getCount(ReportColumn.DATE, ReportColumn.PLACE))
.isEqualTo(1);
}

22. When a Test Name Lies
Should is Better than Test
(korrigiert)
public void shouldOverrideOldReportWithNewValues() {
//given
//when
reportRepository.updateReport(ReportColumn.DATE,
ReportColumn.PLACE, reportMap(BigDecimal.TEN));
reportRepository.updateReport(ReportColumn.DATE,
ReportColumn.PLACE, reportMap(new BigDecimal("5")));
//then
assertThat(reportRepository
.getCount(ReportColumn.DATE, ReportColumn.PLACE))
.isEqualTo(1);
}