Mocking Kotlin with MockK

Introduction to the mocking library MockK

Transcript

1. Mocking Kotlin With MockK Hadi Tok CitizenMe @hadi_tok
2. Unit Testing
3. Unit Testing • Unit: Smallest testable component (function, class) • Units are tested independently from each other • Other units with dependencies are mocked or faked
4. Unit Testing
5. Testable Code • Separations of Concerns • Dependency injection • Clean Code
6. Stub • Returning values without logic. • Could return constant values or use a lookup table
7. Fake • Could have lightweight logic • Cut corners for testing purposes so can’t be used in production
8. Mock Northern mockingbird (Mimus polyglottos)
9. Mock • Not authentic or real, but without the intention to deceive. • Imitates objects to specify behaviour explicitly and enables full control over the object. • Usually backed with a library/framework
10. Mocking • What functions and variables return • Check if the function calls and variable assignments are made with correct values
11. MockK
12. Why MockK • Pure Kotlin • Easy to use Domain Specific Language(DSL) • Can also mock Java
13. Sample
14. data class User(val userId: String, val userName: String)
15. data class User(val userId: String, val userName: String) interface UserApi { fun deleteUser(userId: String): Boolean }
16. data class User(val userId: String, val userName: String) interface UserApi { fun deleteUser(userId: String): Boolean } class UserManager(private val userApi: UserApi) { fun deleteUser(user: User): Boolean { return userApi.deleteUser(user.userId) } }
17. @Test fun basicTest() { val userApi: UserApi = mockk() }
18. @Test fun basicTest() { val userApi: UserApi = mockk() val userManager = UserManager(userApi) }
19. @Test fun basicTest() { val userApi: UserApi = mockk() val userManager = UserManager(userApi) val userId = "123" val user: User = mockk() every { user.userId } returns userId }
20. @Test fun basicTest() { val userApi: UserApi = mockk() val userManager = UserManager(userApi) val userId = "123" val user: User = mockk() every { user.userId } returns userId every { userApi.deleteUser(userId) } returns true }
21. @Test fun basicTest() { val userApi: UserApi = mockk() val userManager = UserManager(userApi) val userId = "123" val user: User = mockk() every { user.userId } returns userId every { userApi.deleteUser(userId) } returns true val result = userManager.deleteUser(user) }
22. @Test fun basicTest() { val userApi: UserApi = mockk() val userManager = UserManager(userApi) val userId = "123" val user: User = mockk() every { user.userId } returns userId every { userApi.deleteUser(userId) } returns true val result = userManager.deleteUser(user) assert(result).toBe(true) }
23. @Test fun basicTest() { val userApi: UserApi = mockk() val userManager = UserManager(userApi) val userId = "123" val user: User = mockk() every { user.userId } returns userId every { userApi.deleteUser(userId) } returns true val result = userManager.deleteUser(user) assert(result).toBe(true) verify { userApi.deleteUser(userId) } }
24. Argument Matching
25. @Test fun basicTest() { val userApi: UserApi = mockk() val userManager = UserManager(userApi) val userId = "123" val user: User = mockk() every { user.userId } returns userId every { userApi.deleteUser(userId) } returns true val result = userManager.deleteUser(user) assert(result).toBe(true) verify { userApi.deleteUser(userId) } }
26. @Test fun basicTest() { val userApi: UserApi = mockk() val userManager = UserManager(userApi) val userId = "123" val user: User = mockk() every { user.userId } returns userId every { userApi.deleteUser(userId) } returns true val result = userManager.deleteUser(user) assert(result).toBe(true) verify { userApi.deleteUser(match { it.startsWith("12") }) } }
27. @Test fun basicTest() { val userApi: UserApi = mockk() val userManager = UserManager(userApi) val userId = "123" val user: User = mockk() every { user.userId } returns userId every { userApi.deleteUser(userId) } returns true val result = userManager.deleteUser(user) assert(result).toBe(true) verify { userApi.deleteUser(any()) } }
28. Matchers • more(), less(), range() • eq(), neq(), refEq(), cmpEq() • isNull(), isNull(inverse=true) • match{}, matchNullable{}
29. Annotations
30. @MockK lateinit var userApi: UserApi @MockK lateinit var user: User val userId = “123" lateinit var userManager:UserManager
31. @MockK lateinit var userApi: UserApi @MockK lateinit var user: User val userId = “123" lateinit var userManager:UserManager @Before fun initTests() { MockKAnnotations.init(this) userManager = UserManager(userApi) every { user.userId } returns userId }
32. @Test fun basicTest() { every { userApi.deleteUser(userId) } returns true val result = userManager.deleteUser(user) assert(result).toBe(true) verify { userApi.deleteUser(userId) } }
33. Object Mock
34. object Calculator { fun add(first: Int, second: Int) = first + second }
35. object Calculator { fun add(first: Int, second: Int) = first + second } @Test fun objectMock() { val result = Calculator.add(1, 2) assert(result).toBe(3) }
36. object Calculator { fun add(first: Int, second: Int) = first + second } @Test fun objectMock() { val result = Calculator.add(1, 2) assert(result).toBe(3) mockkObject(Calculator) every { Calculator.add(1, 2) } returns 42 }
37. object Calculator { fun add(first: Int, second: Int) = first + second } @Test fun objectMock() { val result = Calculator.add(1, 2) assert(result).toBe(3) mockkObject(Calculator) every { Calculator.add(1, 2) } returns 42 }
38. object Calculator { fun add(first: Int, second: Int) = first + second } @Test fun objectMock() { val result = Calculator.add(1, 2) assert(result).toBe(3) mockkObject(Calculator) every { Calculator.add(1, 2) } returns 41 val mockedResult = Calculator.add(1, 2) assert(mockedResult).toBe(42) }
39. Static Mock
40. public class CalculatorStatic { static int add(int first, int second){ return first+second; } }
41. @Test fun staticMock() { val result = CalculatorStatic.add(1, 2) assert(result).toBe(3) }
42. @Test fun staticMock() { val result = CalculatorStatic.add(1, 2) assert(result).toBe(3) mockkStatic(CalculatorStatic::class) }
43. @Test fun staticMock() { val result = CalculatorStatic.add(1, 2) assert(result).toBe(3) mockkStatic(CalculatorStatic::class) every { CalculatorStatic.add(1, 2) } returns 42 }
44. @Test fun staticMock() { val result = CalculatorStatic.add(1, 2) assert(result).toBe(3) mockkStatic(CalculatorStatic::class) every { CalculatorStatic.add(1, 2) } returns 42 val mockedResult = CalculatorStatic.add(1, 2) }
45. @Test fun staticMock() { val result = CalculatorStatic.add(1, 2) assert(result).toBe(3) mockkStatic(CalculatorStatic::class) every { CalculatorStatic.add(1, 2) } returns 42 val mockedResult = CalculatorStatic.add(1, 2) assert(mockedResult).toBe(42) }
46. Argument Capturing
47. class Calculator { fun add(first: Int, second: Int) = first + second }
48. class Calculator { fun add(first: Int, second: Int) = first + second } @Test fun argumentCapturing() { val calculator:Calculator = mockk() }
49. class Calculator { fun add(first: Int, second: Int) = first + second } @Test fun argumentCapturing() { val calculator:Calculator = mockk() every { calculator.add(any(), any()) } answers { firstArg<Int>() + secondArg<Int>() } }
50. class Calculator { fun add(first: Int, second: Int) = first + second } @Test fun argumentCapturing() { val calculator:Calculator = mockk() every { calculator.add(any(), any()) } answers { firstArg<Int>() + secondArg<Int>() } val mockedResult = calculator.add(1, 2) assert(mockedResult).toBe(3) }
51. Coroutines
52. data class User(val userId: String, val userName: String)
53. data class User(val userId: String, val userName: String) interface UserApi { suspend fun deleteUser(userId: String): Boolean }
54. data class User(val userId: String, val userName: String) interface UserApi { suspend fun deleteUser(userId: String): Boolean } class UserManager(private val userApi: UserApi) { suspend fun deleteUser(user: User): Boolean { return userApi.deleteUser(user.userId) } }
55. @MockK lateinit var userApi: UserApi @MockK lateinit var user: User val userId = “123" lateinit var userManager:UserManager @Before fun initTests() { MockKAnnotations.init(this) userManager = UserManager(userApi) every { user.userId } returns userId }
56. @Test fun basicTest() = runBlocking { }
57. @Test fun basicTest() = runBlocking { every { user.userId } returns userId }
58. @Test fun basicTest() = runBlocking { every { user.userId } returns userId coEvery { userApi.deleteUser(userId) } returns true }
59. @Test fun basicTest() = runBlocking { every { user.userId } returns userId coEvery { userApi.deleteUser(userId) } returns true val result = userManager.deleteUser(user) }
60. @Test fun basicTest() = runBlocking { every { user.userId } returns userId coEvery { userApi.deleteUser(userId) } returns true val result = userManager.deleteUser(user) assert(result).toBe(true) coVerify { userApi.deleteUser(userId) } }
61. Other features • Spy • Constructor mock • Extension function mock • Enumeration mock
62. Limitations • final static • inline functions
63. Resources • https://mockk.io/ • Mocking is not rocket science: Basics: https://blog.kotlin-academy.com/mocking-is-not-rocke t-science-basics-ae55d0aadf2b
64. Unit tests without integration tests (Obligatory gif)
65. Questions?
66. Hadi Tok, CitizenMe @hadi_tok Thank you!