Beyond JUnit 5

Transcript

1. https://linktr.ee/jeanneboyarsky 1 Testing: Going Beyond JUnit Jeanne Boyarsky 8/15/25 KCDC speakerdeck.com/boyarsky
2. Gold Sponsors Titanium Sponsors Other Awesome Organizations Platinum Sponsors
3. https://linktr.ee/jeanneboyarsky Book Giveaway at End 3 Java certs: 8/11/17/21 Real World Java
4. https://linktr.ee/jeanneboyarsky Disclaimer 4 Some of the material in this presentation appears in Real World Java.
5. https://linktr.ee/jeanneboyarsky Agenda 5 • Readable Assertions • AssertJ • JUnit Pioneer • Mocking • Selenium • IDE Integration • Patterns/Techniques
6. https://linktr.ee/jeanneboyarsky 6 Readable Assertions
7. https://linktr.ee/jeanneboyarsky What does this output? 7 // public String getFavoriteActivity() { // return "swimming"; // } @Test void summerFunWithPureJUnit() { assertTrue(fun.getFavoriteActivity().startsWith("swim")); assertTrue(fun.getFavoriteActivity().startsWith("tennis")); } org.opentest4j.AssertionFailedError: Expected :true Actual :false
8. https://linktr.ee/jeanneboyarsky Making this better (with JUnit) 8 @Test void summerFunWithReadableOutput() { assertTrue(fun.getFavoriteActivity().startsWith("swim"), "expected to start with 'swim' but was " + fun.getFavoriteActivity()); assertTrue(fun.getFavoriteActivity().startsWith("tennis"), "expected to start with 'tennis' but was " + fun.getFavoriteActivity()); } org.opentest4j.AssertionFailedError: expected to start with 'tennis' but was swimming ==> Expected :true Actual :false
9. https://linktr.ee/jeanneboyarsky Making this better (with Hamcrest) 9 import static org.hamcrest.MatcherAssert.assertThat; import static org.hamcrest.Matchers.*; … @Test void summerFunWithHamcrest() { assertThat(fun.getFavoriteActivity(), startsWith("swim")); assertThat(fun.getFavoriteActivity(), startsWith("tennis")); } java.lang.AssertionError: Expected: a string starting with "tennis" but: was "swimming" Expected :a string starting with "tennis" Actual :"swimming"
10. https://linktr.ee/jeanneboyarsky Making this better (with Hamcrest) 10 import static org.hamcrest.MatcherAssert.assertThat; import static org.hamcrest.Matchers.*; … @Test void summerFunWithHamcrest() { assertThat(fun.getFavoriteActivity(), startsWith("swim")); assertThat(fun.getFavoriteActivity(), startsWith("tennis")); } java.lang.AssertionError: Expected: a string starting with "tennis" but: was "swimming" Expected :a string starting with "tennis" Actual :"swimming"
11. https://linktr.ee/jeanneboyarsky Making this better (with AssertJ) 11 import static org.assertj.core.api.Assertions.assertThat; … @Test void summerFunWithAssertJ() { assertThat(fun.getFavoriteActivity()).startsWith("swim"); assertThat(fun.getFavoriteActivity()).startsWith("tennis"); } java.lang.AssertionError: Expecting actual: "swimming" to start with: "tennis"
12. https://linktr.ee/jeanneboyarsky Adding a custom message (AssertJ) 12 @Test void summerFunMessageWithAssertJ() { assertThat(fun.getFavoriteActivity()) .as("I like swimming").startsWith("swim"); assertThat(fun.getFavoriteActivity()) .as("I like tennis").startsWith("tennis"); } java.lang.AssertionError: [I like tennis] Expecting actual: "swimming" to start with: "tennis" Warning: Placement of as() matters
13. https://linktr.ee/jeanneboyarsky Multiple checks 13 // public List<String> getFavoriteActivities() { // return List.of("swimming", "sunbathing"); // } @Test void summerFunListWithHamcrest() { assertThat(fun.getFavoriteActivities(), hasItem("sunbathing")); assertThat(fun.getFavoriteActivities(), hasSize(2)); } @Test void summerFunListWithAssertJ() { assertThat(fun.getFavoriteActivities()) .contains(“sunbathing") .hasSize(2); }
14. https://linktr.ee/jeanneboyarsky Which more readable? 14 @Test void summerFunListWithHamcrest() { assertThat(fun.getFavoriteActivities(), hasItem("sunbathing")); assertThat(fun.getFavoriteActivities(), hasSize(2)); } @Test void summerFunAllOfHamcrest() { assertThat(fun.getFavoriteActivities(), Matchers.<Collection<String>> allOf( hasSize(2), hasItem("sunbathing") )); }
15. https://linktr.ee/jeanneboyarsky Checking Each Element 15 @Test void summerFunStartingCharacterWithHamcrest() { assertThat(fun.getFavoriteActivities(), everyItem(startsWith("s"))); } @Test void summerFunStartingCharacterWithAssertJ() { assertThat(fun.getFavoriteActivities()) .allSatisfy(w -> assertThat(w).startsWith("s")); }
16. https://linktr.ee/jeanneboyarsky Sample Assertions 16 Hamcrest AssertJ Null nullValue() notNullValue() isNull() isNotNull() Equality is(o) not(o) equalTo() older version isEqualTo(o) isNotEqualTo(o) String startsWith(s) endsWith(s) equalToIgnoringCase(s) startsWith(s) endsWith(s) isEqualToIgnoringCase(s) Collection hasSize(n) hasItems(x) not(hasItem(x)) hasSize(n) contains(x) doesNotContain(x)
17. https://linktr.ee/jeanneboyarsky Comparing 17 Hamcrest • Declarative • Older • Less updates • Multiple or combined assertions • Integration with JUnit 4 assertThat or standalone in JUnit 5 AssertJ • Fluent • Newer • More updates • Chaining assertions (faciliates autocomplete) • Can use with JUnit 4 or 5
18. https://linktr.ee/jeanneboyarsky 18 More on AssertJ
19. https://linktr.ee/jeanneboyarsky Testing Exceptions 19 var actual = assertThrows(ThunderstormException.class, () -> fun.weatherCheck()); assertThat(actual.getMessage().contains(“pool")); assertThrows(IllegalStateException.class, () -> fun.weatherCheck()); org.opentest4j.AssertionFailedError: Unexpected exception type thrown, Expected :class java.lang.IllegalStateException Actual :class com.jeanneboyarsky.example.SummerFun$ThunderstormException
20. https://linktr.ee/jeanneboyarsky Soft Assertions 20 @Test void callingAssertAll() { var softly = new SoftAssertions(); softly.assertThat(“robot") .isEqualTo("izzy"); softly.assertThat(126) .isLessThanOrEqualTo(125); softly.assertAll();; } org.assertj.core.error. AssertJMultipleFailuresError: Multiple Failures (2 failures) -- failure 1 -- expected: "izzy" but was: "robot" at SoftAssertionsTest.calling… -- failure 2 -- Expecting actual: 126 to be less than or equal to: 125 at SoftAssertionsTest.calling…
21. https://linktr.ee/jeanneboyarsky Custom Assertion 21 class CustomAssertions extends AbstractAssert<CustomAssertions, String> { public CustomAssertions(String actual) { super(actual, CustomAssertions.class); } public static CustomAssertions assertThat(String actual) { return new CustomAssertions(actual); } public CustomAssertions isTennis() { if (! "tennis".equals(actual)) failWithMessage("Must be tennis but was %s", actual); return this; } }
22. https://linktr.ee/jeanneboyarsky Calling Custom Assertion 22 void mustBeTennis() { CustomAssertions.assertThat("tennis").isTennis(); CustomAssertions.assertThat("baseball").isTennis(); } java.lang.AssertionError: Must be tennis but was baseball
23. https://linktr.ee/jeanneboyarsky More AssertJ Capabilities 23 • Recursive assertions • More types: • date • path • file • numbers • collections - ex: extract/filter data • etc
24. https://linktr.ee/jeanneboyarsky 24 JUnit Pioneer
25. https://linktr.ee/jeanneboyarsky Disable Until 25 @Test @DisabledUntil(date="2025-10-31", reason = "Need our partner service to be ready") void waitingForServiceAvailability() { … } timestamp = 2025-07-05T11:50:33.673759, DisabledUntil = This test is disabled until 2025-10-31. If executing it on this commit would fail, the build can't be reproduced after that date. The `date` 2025-10-31 is after the current date 2025-07-05
26. https://linktr.ee/jeanneboyarsky Retrying a Test 26 @RetryingTest(10) void flakeyTest() { Random random = new Random(); if (random.nextInt(1, 100) < 75) { fail("too high"); } }
27. https://linktr.ee/jeanneboyarsky System Properties 27 @Test @ClearSystemProperty(key = "JAVA_HOME") void clearProperty() { assertNull(System.getProperty("JAVA_HOME"), "path"); } @Test @SetSystemProperty( key = "JAVA_HOME", value = "c:/java/java21") void maskProperty() { assertEquals("c:/java/java21", System.getProperty("JAVA_HOME")); } Also @SetEnvironmentVariable
28. https://linktr.ee/jeanneboyarsky Creating Combination Tests 28 @CartesianTest void cartesianTest( @CartesianTest.Values(ints = {1, 2}) int time, @CartesianTest.Values(ints = {3, 4}) int tide) { … }
29. https://linktr.ee/jeanneboyarsky More Pioneer Capabilities 29 • System in/out/err • Set detault time zone/locale • Disable selected parameterized tests • Expected to fail (fails if passes) • Parameterized tests with JSON • Temporary directories (also in JUnit) • etc
30. https://linktr.ee/jeanneboyarsky 30 Mocking
31. https://linktr.ee/jeanneboyarsky Test Doubles 31 Term Description Dummy Passed in; never used Fake Some working implementation; simple Stub Contrived responses Spy Merge real and mock behavior Mock Preprogrammed with expectations
32. https://linktr.ee/jeanneboyarsky Class to test 32 public interface ScoreService { int retrieveScore(int matchNumber); } public class Dashboard { private ScoreService service; public Dashboard(ScoreService service) { this.service = service; } public List<Integer> getScores(int maxMatch) { return IntStream.range(1, maxMatch + 1) .mapToObj(n -> service.retrieveScore(n)) .toList(); } }
33. https://linktr.ee/jeanneboyarsky Mockito 33 @ExtendWith(MockitoExtension.class) public class DashboardTest { private Dashboard dashboard; @Mock private ScoreService scoreServiceMock; @BeforeEach void setUp() { dashboard = new Dashboard(scoreServiceMock); }
34. https://linktr.ee/jeanneboyarsky Mockito (cont) 34 @Test void getScores() { when(scoreServiceMock.retrieveScore(1)).thenReturn(76); when(scoreServiceMock.retrieveScore(2)).thenReturn(91); List<Integer> expected = List.of(76, 91); List<Integer> actual = dashboard.getScores(2); assertEquals(expected, actual, "scores"); verify(scoreServiceMock, times(2)).retrieveScore(anyInt()); } }
35. https://linktr.ee/jeanneboyarsky EasyMock 35 @ExtendWith(EasyMockExtension.class) public class DashboardTest { private Dashboard dashboard; @Mock private ScoreService scoreServiceMock; @BeforeEach void setUp() { dashboard = new Dashboard(scoreServiceMock); }
36. https://linktr.ee/jeanneboyarsky EasyMock (cont) 36 @Test void getScores() { expect(scoreServiceMock.retrieveScore(1)).andReturn(76); expect(scoreServiceMock.retrieveScore(2)).andReturn(91); replay(scoreServiceMock); List<Integer> expected = List.of(76, 91); List<Integer> actual = dashboard.getScores(2); assertEquals(expected, actual, "scores"); verify(scoreServiceMock); } }
37. https://linktr.ee/jeanneboyarsky More Mockito Capabilities 37 • Strict or lenient modes • Exceptions • Stubbing • Spies (monitor real objects) • Verify args, # of times API called • Mocking final classes, static methods • etc
38. https://linktr.ee/jeanneboyarsky 38 Selenium
39. https://linktr.ee/jeanneboyarsky Creating driver 39 WebDriver driver = null; try { var options = new ChromeOptions(); options.addArguments("--headless=new"); driver = new ChromeDriver(options); … } finally { if (driver != null) driver.close(); }
40. https://linktr.ee/jeanneboyarsky Reading HTML 40 driver.get("https://www.kcdc.info"); var element = driver.findElement( By.cssSelector(“a[href$='/speakers']")); assertEquals(“https://www.kcdc.info/speakers", element.getAttribute("href"), “url"); assertEquals(“Speakers", element.getAttribute("textContent").strip(), "display name");
41. https://linktr.ee/jeanneboyarsky Dynamic load/longer way 41 driver.get("https://www.kcdc.info/speakers"); var wait = new WebDriverWait(driver, Duration.ofSeconds(60)); wait.until(ExpectedConditions.presenceOfElementLocated( By.tagName("h3"))); boolean match = driver.findElements(By.tagName("h3")) .stream() .anyMatch(e -> "Jeanne Boyarsky".equals(e.getText())); assertTrue(match, "Found Jeanne in speaker list");
42. https://linktr.ee/jeanneboyarsky Locator types 42 • By.id • By.name • By.className • By.tagName • By.cssSelector • By.xpath • By.linkText • By.partialLinkText
43. https://linktr.ee/jeanneboyarsky More Selenium Capabilities 43 • Many browser integrations • Automate clicking/forms • Can capture screenshots • Selenium IDE • Selenium Grid • etc
44. https://linktr.ee/jeanneboyarsky 44 IDE Integration
45. https://linktr.ee/jeanneboyarsky Running Tests (with Coverage) 45 IntelliJ Eclipse VSCode
46. https://linktr.ee/jeanneboyarsky Viewing Code Coverage 46 IntelliJ Eclipse VSCode
47. https://linktr.ee/jeanneboyarsky Viewing a failing assert 47 IntelliJ Eclipse VSCode
48. https://linktr.ee/jeanneboyarsky IntelliJ - Ctrl/Cmd + Shift + T 48
49. https://linktr.ee/jeanneboyarsky Generating Tests 49 Technique Available In Generating class/stub methods Direct in IDE Test Me Generation IntelliJ AI written tests AI plugins
50. https://linktr.ee/jeanneboyarsky 50 Patterns/Techniques
51. https://linktr.ee/jeanneboyarsky AAA 51 • Arrange • Act • Assert
52. https://linktr.ee/jeanneboyarsky Golden Master 52 • Regression test output doesn’t change • Save last good value • text block • file • If changes, decide if correct • Update golden master if so
53. https://linktr.ee/jeanneboyarsky Behavior Driven Development 53 • Given a new conference attendee who wants to eat lunch • When the last morning session ends • Then there will be signage to food
54. https://linktr.ee/jeanneboyarsky Mutation Testing 54 • High code coverage isn’t enough • Run tests many times with mutants • If a mutant is not detected, tests insufficient
55. https://linktr.ee/jeanneboyarsky DRY vs DAMP 55 • DRY: don’t repeat yourself • DAMP: descriptive & meaningful phrases
56. https://linktr.ee/jeanneboyarsky Questions 56 ???
57. https://linktr.ee/jeanneboyarsky Book Giveaway 57
58. https://linktr.ee/jeanneboyarsky The Place to say nice things about me…. 58