This talk is based on heated discussions about the syntax of asserts. Do you like the good old `assertNotEquals(id, c.getId())` or do you prefer something fancier like `assertThat(id, is(not(equalTo(c.getId()))))`? We will take a quick look at the differences between asserts in JUnit, TestNG, Hamcrest, fest, AssertJ, and Spock. This topic is at least as important as Vim vs Emacs and tabs vs spaces! Topic: Software engineering practices Language: English

1. JavaDayCharkiv
Showdown ofthe
Asserts
PhilippKrenn @xeraa

2. Vienna

3. Vienna

4. Vienna

5. Electronic DataInterchange (EDI)

6. ViennaDB
PapersWe LoveVienna

7. AssertDictionary stateafactor
beliefconfidentlyand
forcefully

8. This is
notanassertivetalk

9. Who uses
JUnit

10. Who uses
TestNG

11. Who uses
Hamcrest

12. Who uses
AssertJ

13. Who uses
Spock

14. Who uses
something else

15. Once uponatimewewere using
JUnit

16. Thenwe switchedto
TestNG

17. Thenwe switched backto
JUnit+tempus-fugit

18. tempusfugitlibrary.org
Javamicro-libraryfor
writing &testing
concurrentcode

19. @RunWith(ConcurrentTestRunner.class)
public class ConcurrentTestRunnerTest {
@Test
public void shouldRunInParallel1() {
System.out.println("I'm running on thread " + Thread.currentThread().getName());
}
@Test
public void shouldRunInParallel2() {
System.out.println("I'm running on thread " + Thread.currentThread().getName());
}
@Test
public void shouldRunInParallel3() {
System.out.println("I'm running on thread " + Thread.currentThread().getName());
}
}

20. I'm running on thread ConcurrentTestRunner-Thread-0
I'm running on thread ConcurrentTestRunner-Thread-2
I'm running on thread ConcurrentTestRunner-Thread-1

21. !
try {
Thread.sleep(100);
} catch (InterruptedException e) {
// nothing
}
sleep(millis(100));

22. So unittests looked likethis...
assertNotEquals(unexpected, actual);

23. ...butone dayI found
assertThat(actual, is(not(equalTo(unexpected))));

28. “Declarethe
dependency foryour
favouritetest
frameworkyouwant
to use inyourtests.”
$ gradle init

29. Junit
TestNG
Hamcrest
AssertJ
Truth
Spock

31. JUnitTesting framework

32. TestNGJUnitcompatibletesting
framework

33. HamcrestReplacesJUnit/TestNG
asserts

34. AssertJReplacesJUnit/TestNG
asserts
Fork offest

35. TruthReplacesJUnit/TestNG
asserts

36. SpockTesting framework
written in Groovy
JUnitrunner
Mocking / Stubbing

37. Originalcode
assertNotEquals(unexpected, actual);
assertThat(actual, is(not(equalTo(unexpected))));
» Different order
» Longer
» Additional dependency

38. Minimalexample
public class Adder {
public int add(int a, int b){
return a+b;
}
}

39. JUnit
import org.junit.Test;
import static junit.framework.Assert.assertEquals;
public class Junit {
@Test
public void testAdd(){
Adder adder = new Adder();
assertEquals(3, adder.add(1, 2));
}
}

40. TestNG
import org.testng.annotations.Test;
import static org.testng.Assert.assertEquals;
public class Testng {
@Test
public void testAdd(){
Adder adder = new Adder();
assertEquals(adder.add(1, 2), 3);
}
}

41. Hamcrest
import org.junit.Test;
import static org.hamcrest.MatcherAssert.assertThat;
import static org.hamcrest.Matchers.equalTo;
public class Hamcrest {
@Test
public void testAdd(){
Adder adder = new Adder();
assertThat(adder.add(1, 2), equalTo(3));
}
}

42. AssertJ
import org.junit.Test;
import static org.assertj.core.api.Assertions.assertThat;
public class Assertj {
@Test
public void testAdd(){
Adder adder = new Adder();
assertThat(adder.add(1, 2)).isEqualTo(3);
}
}

43. Truth
import org.junit.Test;
import static com.google.common.truth.Truth.assertThat;
public class Truth {
@Test
public void testAdd(){
Adder adder = new Adder();
assertThat(adder.add(1, 2)).isEqualTo(3);
}
}

44. Spock
class Spock extends spock.lang.Specification {
def "Add two numbers"() {
def adder = new Adder()
expect:
adder.add(1, 2) == 3
}
}

45. Differences

46. JUnit
fail(message)
assertTrue([message,] boolean condition)
assertFalse([message,] boolean condition)
assertEquals([message,] expected, actual)
assertEquals([message,] expected, actual, tolerance)
assertNull([message,] object)
assertNotNull([message,] object)
assertSame([message,] expected, actual)
assertNotSame([message,] expected, actual)

47. JUnitReadability?
Double myPi = 3.14;
assertEquals(
"My own pi is close to the real pi",
Math.PI,
myPi,
0.1)

48. TestNG order ofarguments
import static org.testng.AssertJUnit.*;
import static org.testng.Assert.*;

49. Hamcrest

50. Hamcrest
Double myPi = 3.1;
assertThat(myPi, closeTo(Math.PI, 0.1));

51. Hamcrest
assertThat(new CartoonCharacterEmailLookupService().getResults("looney"),
allOf(
not(empty()),
containsInAnyOrder(
allOf(
instanceOf(Map.class),
hasEntry("id", "56"),
hasEntry("email", "roadrunner@fast.org")),
allOf(
instanceOf(Map.class),
hasEntry("id", "76"),
hasEntry("email", "wiley@acme.com"))
)
));

52. Hamcrestsugar
assertThat(foo, equalTo(bar));
assertThat(foo, is(equalTo(bar)));
assertThat(foo, is(bar));

53. Hamcrestcustom matcher
import org.hamcrest.Description;
import org.hamcrest.Factory;
import org.hamcrest.Matcher;
import org.hamcrest.TypeSafeMatcher;
public class IsNotANumber extends TypeSafeMatcher<Double> {
@Override
public boolean matchesSafely(Double number) {
return number.isNaN();
}
public void describeTo(Description description) {
description.appendText("not a number");
}
@Factory
public static <T> Matcher<Double> notANumber() {
return new IsNotANumber();
}
}

54. Hamcrestcustom matcher
assertThat(1.0, is(notANumber()));
java.lang.AssertionError:
Expected: is not a number
got : <1.0>

55. AssertJ
assertThat(new CartoonCharacterEmailLookupService().getResults("looney"))
.isNotEmpty()
.extracting("id", "email").contains(
tuple("76", "roadrunner@fast.org"),
tuple("56", "wiley@acme.com"));

56. AssertJ
Double myPi = 3.1;
assertThat(myPi).isCloseTo(Math.PI, Percentage.withPercentage(3));

57. Truth
assertThat(new CartoonCharacterEmailLookupService().getResults("looney"))
.containsEntry("id", "76");

58. Truth
Truth.ASSERT
Truth.ASSUME
Expect.create()

59. Truth
Double myPi = 3.1;
assertThat(myPi).isWithin(0.1).of(Math.PI);

60. Spock
when:
stack.push(elem)
then:
!stack.empty
stack.size() == 1
stack.peek() == elem

61. Spock
def "length of Spock's and his friends' names"() {
expect:
name.size() == length
where:
name | length
"Spock" | 5
"Kirk" | 4
"Scotty" | 6
}

62. Spockwith Hamcrestmatcher
def "comparing two decimal numbers"() {
def myPi = 3.14
expect:
myPi closeTo(Math.PI, 0.1)
}

63. Conclusion

64. It'samessOrder ofarguments

65. It'samessTraditionalvs
fluentinterfaces

66. It'samessDifferentstyles

67. Stickto one
technology(combination)
style

68. “Wantto getmuch
better atwriting unit
tests? Forthe next
week,trywriting every
singleassertion using
equal()”
https://medium.com/javascript-scene/what-every-unit-test-
needs-f6cd34d9836d

69. PS:There is no maybe
intests

70. Thanks
Questions?@xeraa

71. Image Credit
» Schnitzel https://flic.kr/p/9m27wm
» Architecture https://flic.kr/p/6dwCAe
» Conchita https://flic.kr/p/nBqSHT
» Paper: http://www.freeimages.com/photo/432276