Coroutines IV : Deep Dive Into Coroutine Testing

These are the slides for the last session on coroutines. In this session I how we can test suspending functions and functions that launch coroutines using coroutine builders.

Transcript

1. Deep Dive Into Coroutine Testing @mambo_bryan 01
2. 02 Design Centric Engineer Brian Odhiambo Dishwasher @ Baobab Circle Co-organizer @ KotlinKenya Maintaining @ KotlinBits Crazy about that UI/UX & Kotlin
3. Ensuring It Works 03 testing! assertions! failures! Suspending Functions Testing functions that immediately return a value Non Suspending Functions Testing functions that launch other coroutines
4. What are coroutines? What are coroutine builders? A Small Recap Why use coroutines? What is a coroutine context, why do we need it? What are jobs, and their state? What are dispatchers and how do they help? And So much more... Just like DSTV
5. Testing The theory of testing
6. improve code quality detect vulnerabilities detect edge cases early being kind to the next developer so on & so forth Evaluating and verifying the accuracy of your code What is testing? Why should we test?
7. improve code quality detect vulnerabilities detect edge cases early being kind to the next developer so on & so forth Evaluating and verifying the accuracy of your code What is testing? Why should we test? action performed WHEN expected outcome of the action SHOULD Thing under test GIVEN
8. Example fun add(a : Int, b : Int) = a.plus(b) fun main() { // given & when val actual = add(1, 2) val expected = 3 // should if(expected != actual) println("Test Failed !") else println("Test Passed...") } 06
9. runBlocking { ... } runBlockingTest { ... } Evolution Of kotlinx.coroutines.test runTest { ... }
10. Suspending Testing suspended functions
11. suspend fun fetchAuthors() { delay(1_500L) return listOf("a", "b", "c") } @Test fun fetchAuthorsTest(){ val list = fetchAuthors() assertContains(list, "a") } 06
12. suspend fun fetchAuthors() { delay(1_500L) return listOf("a", "b", "c") } @Test fun fetchAuthorsTest(){ val list = fetchAuthors() assertContains(list,"a") } 06
13. import kotlinx.coroutines.text.runTest suspend fun fetchAuthors() { delay(1_500L) return listOf("a", "b", "c") } @Test fun fetchAuthorsTest() = runTest { val list = fetchAuthors() assertContains(list,"a") } 06
14. import kotlinx.coroutines.text.runTest suspend fun fetchAuthors() = withContext(Dispatchers.IO) { delay(1_500L) return listOf("a", "b", "c") } @Test fun fetchAuthorsTest() = runTest { val list = fetchAuthors() assertContains(list,"a") } 06
15. New Coroutines Those fire & forget coroutines
16. runBlocking { ... } runBlockingTest { ... } runTest { ... } TestCoroutineScheduler TestDispatcher Evolution Of kotlinx.coroutines.test runTest { ... } TestScope
17. import kotlinx.coroutines.text.runTest suspend fun fetchAuthors(dispatcher: CoroutineContext) = withContext(dispatcher) { delay(1_500L) return listOf("a", "b", "c") } @Test fun fetchAuthorsTest() = runTest { val list = fetchAuthors(testDispatcher) assertContains(list,"a") } 06
18. import kotlinx.coroutines.text.runTest ... fun addAuthors() { launch { database.add("a") } launch { database.add("b") } } fun fetchAuthors(){ return authors } ... @Test fun fetchAuthorsTest() = runTest { val repo = AuthorRepository() repo.addAuthors() val list = fetchAuthors() assertContains(list,"a") } 06
19. import kotlinx.coroutines.text.runTest ... fun addAuthors() { launch { database.add("a") } launch { database.add("b") } } fun fetchAuthors(){ return authors } ... @Test fun fetchAuthorsTest() = runTest { val repo = AuthorRepository() repo.addAuthors() val list = fetchAuthors() assertContains(list,"a") } 06
20. starts job immediately use selectively UnconfinedTestDispatcher default dispatcher queues work StandardTestDispatcher TestDispatchers
21. import kotlinx.coroutines.text.runTest ... fun addAuthors() { launch { database.add("a") } launch { database.add("b") } } fun fetchAuthors(){ return authors } ... @Test fun fetchAuthorsTest() = runTest { val repo = AuthorRepository() repo.addAuthors() advanceUntilIdle() val list = fetchAuthors() assertContains(list,"a") } 06
22. import kotlinx.coroutines.text.runTest ... fun addAuthors() { launch { database.add("a") } launch { database.add("b") } } fun fetchAuthors(){ return authors } ... @Test fun fetchAuthorsTest() = runTest(UnconfinedTestDispatcher()) { val repo = AuthorRepository() repo.addAuthors() // advanceUntilIdle() val list = fetchAuthors() assertContains(list,"a") } 06
23. import kotlinx.coroutines.text.runTest class AuthRepository(scope: CoroutineContext){ fun addAuthors() { scope.launch { database.add("a") } scope.launch { database.add("b") } } fun fetchAuthors(){ return authors } ... @Test fun fetchAuthorsTest() = runTest() { val repo = AuthorRepository(testDispatcher) repo.addAuthors() val list = fetchAuthors() assertContains(list,"a") } 06
24. One Last Thing For the community
25. KotlinBits 😎 A fun and easy way to learn Kotlin in small bits and pieces. React, Comment & Share https://kotlinbits.vercel.app
26. Thank you So much DroidPwani. You guys have been awesome & fantastic
27. 16 mambo_bryan MamboBryan Have a nice Kotlin KotlinBits kotlinbits.vercel.app