MockK: mocking library for Kotlin

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1. mocking libaray for Kotlin Joe Tsai 2018.09.20 @ Android Taipei
2. Joe Tsai Android Developer https://medium.com/joe-tsai
3. Kotlin + Mockito 可能會遇到的問題
4. 嘗試 @mock Class org.mockito.exceptions.base.MockitoException: Cannot mock/spy class com.joetsai.kotlinunittest.token.TokenRepository Mockito cannot mock/spy because : - final class
5. 嘗試 @mock Class org.mockito.exceptions.base.MockitoException: Cannot mock/spy class com.joetsai.kotlinunittest.token.TokenRepository Mockito cannot mock/spy because : - final class → 在 Kotlin 中任何 Class 預設為 final 解法 1. Open class 2. 開啟隱藏版 mock final 功能
6. 其他可能遇到的問題 • java.lang.IllegalStateException: anyObject() must not be null any(), eq(), capture(), captor() • `when` 解法 1. MockitoKotlinHelpers.kt 2. Mockito-Kotlin
7. 測試 static 方法（PowerMock） • 初始化繁瑣，使用上不直覺 • “Mockito2 support is currently experimental. A lot of issues are not resolved still.” 版本兼容性
8. 只是想用 Kotlin 寫單元測試而已 有必要這麼折磨人嗎？
9. 如果不用處理上述問題又可以測試靜態方法， 該有多好？
10. 無痛在 Kotlin 下使用 Mockito + PowerMock
11. Gradle Setting dependencies { testImplementation 'io.mockk:mockk:1.8.6' ... }
12. Example: 小孩要零用錢 class Kid(private val mother: Mother) { var money = 0 private set fun wantMoney() { money += mother.giveMoney() } } class Mother { fun giveMoney(): Int { return 100 } }
13. mockk, every class KidTest { @Test fun wantMoney() { // Given val mother = mockk<Mother>() val kid = Kid(mother) every { mother.giveMoney() } returns 30 // when().thenReturn() in Mockito // When kid.wantMoney() // Then assertEquals(30, kid.money) } }
14. Annotation class KidAnnotationTest { @MockK lateinit var mother: Mother lateinit var kid: Kid @Before fun setUp() { MockKAnnotations.init(this) kid = Kid(mother) } @Test fun wantMoney() { every { mother.giveMoney() } returns 30 kid.wantMoney() assertEquals(30, kid.money) } }
15. 需求變更：通知媽媽 class Kid(private val mother: Mother) { var money = 0 private set fun wantMoney() { mother.inform(money) money += mother.giveMoney() } } class Mother { fun inform(money: Int) { println("媽媽我現在有 $money 元，我要跟你拿錢！") } fun giveMoney(): Int { return 100 } }
16. Verify @Test fun wantMoney() { // When val mother = mockk<Mother>() val kid = Kid(mother) every { mother.giveMoney() } returns 30 // Given kid.wantMoney() // Then verify { mother.inform(any()) } assertEquals(30, kid.money) }
17. Verify @Test fun wantMoney() { // When val mother = mockk<Mother>() val kid = Kid(mother) every { mother.giveMoney() } returns 30 // Given kid.wantMoney() // Then verify { mother.inform(any()) } assertEquals(30, kid.money) } io.mockk.MockKException: no answer found for: Mother(#1).inform(0)
18. Verify @Test fun wantMoney() { // When val mother = mockk<Mother>() val kid = Kid(mother) every { mother.giveMoney() } returns 30 // Given kid.wantMoney() // Then verify { mother.inform(any()) } assertEquals(30, kid.money) } io.mockk.MockKException: no answer found for: Mother(#1).inform(0) 在 MockK 預設的 mock 是很嚴謹的，必須指定所 有的行為操作。
19. Verify @Test fun wantMoney() { // When val mother = mockk<Mother>() val kid = Kid(mother) every { mother.giveMoney() } returns 30 // Given kid.wantMoney() // Then verify { mother.inform(any()) } assertEquals(30, kid.money) } io.mockk.MockKException: no answer found for: Mother(#1).inform(0) 在 MockK 預設的 mock 是很嚴謹的，必須指定所 有的行為操作。 every { mother.inform(any()) } just Runs
20. Relaxed Mocks 該物件所有的方法都不需要指定 // 第一種 val mother = mockk<Mother>(relaxed = true) // 第二種 @RelaxedMockK lateinit var mother: Mother
21. Relaxed Unit Function 不需指定無回傳值的方法 @MockK lateinit var mother: Mother @Before fun setUp() { MockKAnnotations.init(this, relaxUnitFun = true) } @MockK(relaxUnitFun = true) lateinit var mother: Mother
22. Verify verify { mother.inform(any()) } verify(exactly = 0) { mother.inform(any()) } verify { mother.inform(any()) mother.giveMoney() } // inform() 的下一個執行的方法一定要是 giveMoney() verifySequence { mother.inform(any()) mother.giveMoney() } // inform() 只要在 giveMoney() 之前執行即可 verifyOrder { mother.inform(any()) mother.giveMoney() }
23. Capture 用途：抓取方法參數 種類：slot, mutableListOf class Mother { fun inform(money: Int) { println("媽媽我現在有 $money 元，我要跟你拿錢！") } ... } val slot = slot<Int>() every { mother.inform(capture(slot)) } just Runs kid.wantMoney() assertEquals(0, slot.captured)
24. Static Method class Util { fun ok() { UtilJava.ok() UtilKotlin.ok() } } object UtilKotlin { @JvmStatic fun ok(): String { return "UtilKotlin.ok()" } } public class UtilJava { static String ok() { return "UtilJava.ok()"; } }
25. @Test fun ok() { // Given val util = Util() mockkStatic(UtilJava::class) mockkStatic(UtilKotlin::class) every { UtilJava.ok() } returns "Joe" every { UtilKotlin.ok() } returns "Tsai" // When util.ok() // Then verify { UtilJava.ok() } verify { UtilKotlin.ok() } assertEquals("Joe", UtilJava.ok()) assertEquals("Tsai", UtilKotlin.ok()) } MockkStatic
26. Companion Object ? class Util { fun ok() { UtilKotlin.ok() } } class UtilKotlin { companion object { @JvmStatic fun ok(): String { return "UtilKotlin.ok()" } } }
27. Test Companion Object @Test fun ok() { // Given val util = Util() mockkObject(UtilKotlin) mockkObject(UtilKotlin.Companion) every { UtilKotlin.ok() } returns "Tsai" // When util.ok() // Then verify { UtilKotlin.ok() } assertEquals("Tsai", UtilKotlin.ok()) } 兩個都能正常運作
28. class Util { fun ok() { UtilKotlin.ok() } } Singleton object UtilKotlin { @JvmStatic fun ok(): String { return "UtilKotlin.ok()" } }
29. MockkObject @Test fun ok() { // Given val util = Util() mockkObject(UtilKotlin) every { UtilKotlin.ok() } returns "Tsai" // When util.ok() // Then verify { UtilKotlin.ok() } assertEquals("Tsai", UtilKotlin.ok()) }
30. What’s More • Spy • Extension functions • Private functions • Coroutines
31. Reference • MockK.io • MOCKING IN KOTLIN WITH MOCKK • Kotlin: Static Methods
32. Let’s mockK