The document discusses best practices in testing software, highlighting the importance of effective tests that verify functionality while avoiding common pitfalls such as fragile, redundant, or trivial tests. It emphasizes the need for comprehensive testing strategies that include assertions, better naming conventions for tests, and proper documentation of test cases. Various examples illustrate how to write and improve tests in a way that ensures reliability and clarity in expected outcomes.

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);
}