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Use cases with Flow
interface FlowProvider {
fun returnsAColdFlow(): Flow<Int> = flow {
repeat(5) {
emit(it)
delay(100)
}
}
}
object DefaultFlowProvider : FlowProvider
class FlowPlayground(private val flowProvider: FlowProvider = DefaultFlowProvider) {
val globalScope: CoroutineScope = CoroutineScope(EmptyCoroutineContext)
val flowOf: Flow<Int> = flowOf(1, 2, 3, 4, 5)
fun sharedFlow(coroutineScope: CoroutineScope): SharedFlow<Int> = flowOf.shareIn(coroutineScope, SharingStarted.Eagerly, 0)
val sharedFlowEagerly: SharedFlow<Int> = flowOf.shareIn(globalScope, SharingStarted.Eagerly, 1)
val sharedFlowLazily: SharedFlow<Int> = flowOf.shareIn(globalScope, SharingStarted.Lazily, 1)
val sharedFlowWhileSubscribed: SharedFlow<Int> = flowOf.shareIn(globalScope, SharingStarted.WhileSubscribed(), 1)
suspend fun stateFlow(coroutineScope: CoroutineScope): StateFlow<Int> = flowOf.stateIn(coroutineScope)
fun stateFlow2(coroutineScope: CoroutineScope): StateFlow<Int> = flowOf.stateIn(coroutineScope, SharingStarted.Lazily, 0)
val stateFlowLazily: StateFlow<Int> = flowOf.stateIn(globalScope, SharingStarted.Lazily, 0)
val stateFlowEagerly: StateFlow<Int> = flowOf.stateIn(globalScope, SharingStarted.Eagerly, 0)
val stateFlowWhileSubscribed: StateFlow<Int> = flowOf.stateIn(globalScope, SharingStarted.WhileSubscribed(), 0)
val transformColdFlowToHotFlow: StateFlow<Int> =
flowProvider.returnsAColdFlow()
.drop(1)
.map { it * 2 }
.stateIn(globalScope, SharingStarted.Lazily, 0)
}
class FlowPlaygroundTest : StringSpec({
"cold flow to hot flow" {
val sut = FlowPlayground()
sut.transformColdFlowToHotFlow.test {
expectItem() shouldBe 0
expectItem() shouldBe 2
expectItem() shouldBe 4
expectItem() shouldBe 6
}
}
"cold flow to hot flow - with mockk" {
val sut = FlowPlayground(mockk {
every { returnsAColdFlow() } returns flowOf(7, 8, 9)
})
sut.transformColdFlowToHotFlow.test {
expectItem() shouldBe 0
expectItem() shouldBe 16
expectItem() shouldBe 18
cancelAndConsumeRemainingEvents()
}
}
"flowOf" {
FlowPlayground().flowOf.test {
expectItem() shouldBe 1
expectItem() shouldBe 2
expectItem() shouldBe 3
expectItem() shouldBe 4
expectItem() shouldBe 5
expectComplete()
}
}
"shared flow - function" {
coroutineScope {
FlowPlayground().sharedFlow(this).test {
expectItem() shouldBe 1
expectItem() shouldBe 2
expectItem() shouldBe 3
expectItem() shouldBe 4
expectItem() shouldBe 5
cancelAndConsumeRemainingEvents()
}
}
}
"shared flow eagerly" {
val sut = FlowPlayground()
sut.sharedFlowEagerly.test {
expectItem() shouldBe 5
cancelAndConsumeRemainingEvents()
}
sut.sharedFlowEagerly.test {
expectItem() shouldBe 5
cancelAndConsumeRemainingEvents()
}
}
"shared flow lazily" {
val sut = FlowPlayground()
sut.sharedFlowLazily.test {
expectItem() shouldBe 1
expectItem() shouldBe 2
expectItem() shouldBe 3
expectItem() shouldBe 4
expectItem() shouldBe 5
cancelAndConsumeRemainingEvents()
}
sut.sharedFlowLazily.test {
expectItem() shouldBe 5
cancelAndConsumeRemainingEvents()
}
}
"shared flow while subscribed" {
val sut = FlowPlayground()
sut.sharedFlowWhileSubscribed.test {
expectItem() shouldBe 1
expectItem() shouldBe 2
expectItem() shouldBe 3
expectItem() shouldBe 4
expectItem() shouldBe 5
cancelAndConsumeRemainingEvents()
}
sut.sharedFlowWhileSubscribed.test {
expectItem() shouldBe 5
cancelAndConsumeRemainingEvents()
}
}
"state flow - function" {
coroutineScope {
val sut = FlowPlayground()
sut.stateFlow(this).test {
expectItem() shouldBe 5
cancelAndConsumeRemainingEvents()
}
}
}
"state flow 2 - function" {
coroutineScope {
val sut = FlowPlayground()
sut.stateFlow2(this).test {
expectItem() shouldBe 0
expectItem() shouldBe 1
expectItem() shouldBe 2
expectItem() shouldBe 3
expectItem() shouldBe 4
expectItem() shouldBe 5
cancelAndConsumeRemainingEvents()
}
sut.stateFlow2(this).test {
expectItem() shouldBe 0
expectItem() shouldBe 1
expectItem() shouldBe 2
expectItem() shouldBe 3
expectItem() shouldBe 4
expectItem() shouldBe 5
cancelAndConsumeRemainingEvents()
}
}
}
"state flow - lazily" {
val sut = FlowPlayground()
sut.stateFlowLazily.test {
expectItem() shouldBe 0
expectItem() shouldBe 1
expectItem() shouldBe 2
expectItem() shouldBe 3
expectItem() shouldBe 4
expectItem() shouldBe 5
cancelAndConsumeRemainingEvents()
}
sut.stateFlowLazily.test {
expectItem() shouldBe 5
cancelAndConsumeRemainingEvents()
}
}
"state flow - eagerly" {
val sut = FlowPlayground()
sut.stateFlowEagerly.test {
expectItem() shouldBe 5
cancelAndConsumeRemainingEvents()
}
sut.stateFlowEagerly.test {
expectItem() shouldBe 5
cancelAndConsumeRemainingEvents()
}
}
"state flow - while subscribed" {
val sut = FlowPlayground()
sut.stateFlowWhileSubscribed.test {
expectItem() shouldBe 0
expectItem() shouldBe 1
expectItem() shouldBe 2
expectItem() shouldBe 3
expectItem() shouldBe 4
expectItem() shouldBe 5
cancelAndConsumeRemainingEvents()
}
sut.stateFlowWhileSubscribed.test {
expectItem() shouldBe 5
cancelAndConsumeRemainingEvents()
}
}
})
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