Improve your tests using Kotlin.

Improve your tests using Kotlin Fábio Carballo @fabiocarballo

Why Kotlin?…

• Immutability first

• Immutability first • Hides Nullability

• Immutability first • Hides Nullability • Allows extensions to
third-party classes

• Immutability first • Hides Nullability • Allows extensions to
third-party classes • High-order functions / Lambdas

Still afraid?… Use Kotlin in your tests.

• Mockito testCompile 'org.mockito:mockito-core:2.8.9' • Kotlin JUnit Assertions testCompile org.jetbrains.kotlin:kotlin-test-junit:${kotlinVersion}

class Greeter( private val user: User) { fun getEnglishGreeting() =
"Hello, ${user.fullName()}!" } class User( private val firstName: String, private val lastName: String) { fun fullName(): String = "$firstName $lastName" }

class GreeterTest { @Mock lateinit var user: User lateinit var
tested: Greeter @Before fun setUp() { MockitoAnnotations.initMocks(this) tested = Greeter(user) } @Test fun englishGreetIsCorrect() { Mockito.`when`(user.fullName()).thenReturn("Fábio Carballo") assertEquals("Hello, Fábio Carballo!", tested.getEnglishGreeting()) } }

tested: Greeter @Before fun setUp() { MockitoAnnotations.initMocks(this) tested = Greeter(user) } @Test fun englishGreetIsCorrect() { Mockito.`when`(user.fullName()).thenReturn("Fábio Carballo") assertEquals("Hello, Fábio Carballo!", tested.getEnglishGreeting()) } } org.mockito.exceptions.base.MockitoException: Cannot mock/spy class fabiocarballo.com.myapplication.User Mockito cannot mock/spy because : - ﬁnal class

• Use Interfaces interface User { fun fullName(): String }

• “Open” Classes open class User( private val firstName: String,
private val lastName: String) { open fun fullName(): String = "$firstName $lastName" }

• Use Mockito 2.2.X

Mockito.verify(user).addFriend(Mockito.any()) class User( private val firstName: String, private val lastName:
String) { fun addFriend(friend: User) { … } }

String) { fun addFriend(friend: User) { … } } Mockito Matchers rely on null-values.

String) { fun addFriend(friend: User) { … } } Mockito Matchers rely on null-values. Mockito.verify(user).addFriend(null)

mockito-kotlin https://github.com/nhaarman/mockito-kotlin

mockito-kotlin verify(user).addFriend(any()) anyOrNull() anyVarArg() anyArray()

mockito-kotlin Mockito.`when`(user.fullName()).thenReturn(“Fábio Carballo”)

mockito-kotlin Mockito.`when`(user.fullName()).thenReturn(“Fábio Carballo”) whenever(user.fullName()).thenReturn(“Fábio Carballo”)

mockito-kotlin val user: User = Mockito.mock(User::class)

mockito-kotlin val user: User = Mockito.mock(User::class) val user: User =
mock()

mockito-kotlin val user: User = Mockito.mock(User::class) val user: User =
mock() val user: User = mock { on { fullName() }.thenReturn(“Fábio Carballo”) }

tested: Greeter @Before fun setUp() { MockitoAnnotations.initMocks(this) tested = Greeter(user) } @Test fun englishGreetIsCorrect() { Mockito.`when`(user.fullName()).thenReturn("Fábio Carballo") assertEquals("Hello, Fábio Carballo!", tested.getEnglishGreeting()) } }

class GreeterTest { val user: User = mock() val tested
= Greeter(user) @Test fun englishGreetIsCorrect() { whenever(user.fullName()).thenReturn("Fábio Carballo") assertEquals("Hello, Fábio Carballo!", tested.getEnglishGreeting()) } }

class GreeterTest { val user: User = mock() val tested
= Greeter(user) @Test fun englishGreetIsCorrect() { whenever(user.fullName()).thenReturn("Fábio Carballo") assertEquals("Hello, Fábio Carballo!", tested.getEnglishGreeting()) } } class GreeterTest { val user: User = mock { on { fullName() }.thenReturn("Fábio Carballo") } val tested = Greeter(user) @Test fun englishGreetIsCorrect() { assertEquals("Hello, Fábio Carballo!", tested.getEnglishGreeting()) } }

Kotlin Quick-Wins

@Test fun test_addFriend_userHasNoFriends_FriendsListShouldNotBeEmpty() { … }

@Test fun test_addFriend_userHasNoFriends_FriendsListShouldNotBeEmpty() { … } @Test fun `when user
has no friends and a friend is added the friends list should not be empty`() { … }

class ServiceA { fun methodA() { … } } class
ServiceB { fun methodB() { … } } class Test { fun test() { val serviceA: ServiceA = mock() val serviceB: ServiceB = mock() serviceA.methodA() serviceB.methodB() val inOrder = inOrder(serviceA, serviceB) inOrder.verify(serviceA).methodA() inOrder.verify(serviceB).methodB() } }

class ServiceA { fun methodA() { … } } class
ServiceB { fun methodB() { … } } class Test { fun test() { val serviceA: ServiceA = mock() val serviceB: ServiceB = mock() serviceA.methodA() serviceB.methodB() inOrder(serviceA, serviceB).apply { verify(serviceA).methodA() verify(serviceB).methodB() } } }

kluent https://github.com/MarkusAmshove/Kluent expekt https://github.com/winterbe/expekt

data class User( private val firstName: String, private val lastName:
String, private val age: Int) { val fullName = "$firstName $lastName" val canDrink = (age >= 18) val friends: MutableList<User> = mutableListOf() fun addFriend(user: User) { if (user !in friends) { friends.add(user) user.addFriend(this) } } }

@Test fun `the full name is the concatenation of the
first and last name`() { val user = User(firstName = "Fábio", lastName = "Carballo", age = 26) assertEquals("Fábio Carballo", user.fullName) }

first and last name`() { val user = User(firstName = "Fábio", lastName = "Carballo", age = 26) assertEquals("Fábio Carballo", user.fullName) user.fullName `should equal` "Fábio Carballo” // Kluent }

first and last name`() { val user = User(firstName = "Fábio", lastName = "Carballo", age = 26) assertEquals("Fábio Carballo", user.fullName) user.fullName `should equal` "Fábio Carballo” // Kluent } infix fun Any.`should equal`(theOther: Any) = assertEquals(theOther, this)

first and last name`() { val user = User(firstName = "Fábio", lastName = "Carballo", age = 26) assertEquals("Fábio Carballo", user.fullName) user.fullName `should equal` "Fábio Carballo” // Kluent user.fullName.should.equal(“Fábio Carballo”) // Expect }

@Test fun `friends are correctly added`() { val rui =
User(firstName = "Rui", lastName = "Gonçalo", age = 28) val fabio = User(firstName = "Fábio", lastName = "Carballo", age = 26) rui.addFriend(fabio) assertEquals(listOf(fabio), rui.friends) // OR assertTrue { fabio in rui.friends } }

User(firstName = "Rui", lastName = "Gonçalo", age = 28) val fabio = User(firstName = "Fábio", lastName = "Carballo", age = 26) rui.addFriend(fabio) assertEquals(listOf(fabio), rui.friends) // KLUENT rui.friends `should contain` fabio rui.friends `should not contain` rui }

User(firstName = "Rui", lastName = "Gonçalo", age = 28) val fabio = User(firstName = "Fábio", lastName = "Carballo", age = 26) rui.addFriend(fabio) assertEquals(listOf(fabio), rui.friends) // KLUENT rui.friends `should contain` fabio rui.friends `should not contain` rui // EXPEKT rui.friends.should.contain(fabio) }

User(firstName = "Rui", lastName = "Gonçalo", age = 28) val fabio = User(firstName = "Fábio", lastName = "Carballo", age = 26) rui.addFriend(fabio) assertEquals(listOf(fabio), rui.friends) // KLUENT rui.friends `should contain` fabio rui.friends `should not contain` rui // EXPEKT rui.friends.should.contain(fabio) fabio.friends.should.have.all.elements(rui).and.have.size(1) }

User(firstName = "Rui", lastName = "Gonçalo", age = 28) val fabio = User(firstName = "Fábio", lastName = "Carballo", age = 26) rui.addFriend(fabio) assertEquals(listOf(fabio), rui.friends) // KLUENT rui.friends `should contain` fabio rui.friends `should not contain` rui // EXPEKT rui.friends.should.contain(fabio) fabio.friends.should.have.all.elements(rui).and.have.size(1) expect(rui.friends).to.contain(fabio) }

fun drink() { if (canDrink) { System.out.println("Drinking .. ") }
else { throw UnderageDrinkingException() } } class UnderageDrinkingException() : Exception("You can't drink.")

else { throw UnderageDrinkingException() } } class UnderageDrinkingException() : Exception("You can't drink.") @Test(expected = UnderageDrinkingException::class) fun `an underage user can't drink`() { val ricardo = User( firstName = "Ricardo", lastName = "Trindade", age = 17) ricardo.drink() }

else { throw UnderageDrinkingException() } } class UnderageDrinkingException() : Exception("You can't drink.") fun `an underage user can't drink`() { val ricardo = User( firstName = "Ricardo", lastName = "Trindade", age = 17) val ricardoDrinks = { ricardo.drink() }    ricardoDrinks `should throw` UnderageDrinkingException::class }

else { throw UnderageDrinkingException() } } class UnderageDrinkingException() : Exception("You can't drink.") fun `an underage user can't drink`() { val ricardo = User( firstName = "Ricardo", lastName = "Trindade", age = 17) val ricardoDrinks = { ricardo.drink() }    ricardoDrinks `should throw the Exception` UnderageDrinkingException::class `with message` "You can't drink." }

Spek https://github.com/spekframework/spek

• JUnit tests have a flat structure • RSpec •
TDD test framework for Kotlin

@RunWith(JUnitPlatform::class) class SimpleSpec : Spek({ it("should be true") { true
`should be` true } })

Hangman •Player 1 thinks about an arbitrary word. •Other players
try to guess the word by suggesting a letter. •Each wrong guess, a part of the hangman is drawn.

class Hangman(private val word: String) { var wrongAnswerCount = 0
fun suggestLetter(letter: Char): Boolean { … } }

• Feature description • describe -> it

@RunWith(JUnitPlatform::class) class HangmanFeatureSpec : Spek({ val game = Hangman("apple") describe("letter
verification") { it("returns true when the suggestion is correct") { game.suggestLetter('a') `should equal` true } it("returns false when the suggestion is incorrect") { game.suggestLetter('f') `should equal` false } } })

• Behavior description • given -> on -> it

@RunWith(JUnitPlatform::class) class HangmanBehaviorSpec : Spek({ val hiddenWord = "apple" given("a
new game with the hidden word being $hiddenWord:") { val game = Hangman(hiddenWord) on(“correct suggestion") { game.suggestLetter(‘a’) it("has no wrong answers") { game.wrongAnswerCount `should equal` 0 } it("shows the guessed letters") { game.dashedWord `should equal` "a----" } } } })

Scopes • Tests (it)

Scopes • Tests (it) • Group (given, describe, context, group)

fun SpecBody.describe(description: String, body: SpecBody.() -> Unit) { group("describe $description",
body = body) } fun SpecBody.context(description: String, body: SpecBody.() -> Unit) { group("context $description", body = body) } fun SpecBody.given(description: String, body: SpecBody.() -> Unit) { group(“given $description", body = body) }

Scopes • Tests (it) • Group (given, describe, context, group)
• Action (on)

Ignoring tests • Just add an X as a prefix
to the scope xit("returns true when the suggestion is correct") { game.suggestLetter('a') `should equal` true }

Thank you. Questions?

Improve your tests using Kotlin.

Improve your tests using Kotlin.

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