StateFlow stress tests (#2857)

Author: qwwdfsad

kotlinx-coroutines-core/concurrent/test/StateFlowCommonStressTest.kt

@@ -0,0 +1,47 @@
+/*
+ * Copyright 2016-2020 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
+ */
+
+package kotlinx.coroutines.flow
+
+import kotlinx.coroutines.*
+import kotlin.random.*
+import kotlin.test.*
+
+// Simplified version of StateFlowStressTest
+class StateFlowCommonStressTest : TestBase() {
+    private val state = MutableStateFlow<Long>(0)
+
+    @Test
+    fun testSingleEmitterAndCollector() = runTest {
+        var collected = 0L
+        val collector = launch(Dispatchers.Default) {
+            // collect, but abort and collect again after every 1000 values to stress allocation/deallocation
+            do {
+                val batchSize = Random.nextInt(1..1000)
+                var index = 0
+                val cnt = state.onEach { value ->
+                    // the first value in batch is allowed to repeat, but cannot go back
+                    val ok = if (index++ == 0) value >= collected else value > collected
+                    check(ok) {
+                        "Values must be monotonic, but $value is not, was $collected"
+                    }
+                    collected = value
+                }.take(batchSize).map { 1 }.sum()
+            } while (cnt == batchSize)
+        }
+
+        var current = 1L
+        val emitter = launch {
+            while (true) {
+                state.value = current++
+                if (current % 1000 == 0L) yield() // make it cancellable
+            }
+        }
+
+        delay(3000)
+        emitter.cancelAndJoin()
+        collector.cancelAndJoin()
+        assertTrue { current >= collected / 2 }
+    }
+}

kotlinx-coroutines-core/concurrent/test/StateFlowUpdateCommonTest.kt

@@ -0,0 +1,38 @@
+/*
+ * Copyright 2016-2021 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
+ */
+
+package kotlinx.coroutines.flow
+
+import kotlinx.coroutines.*
+import kotlin.test.*
+import kotlin.test.Test
+
+class StateFlowUpdateCommonTest : TestBase() {
+    private val iterations = 100_000 * stressTestMultiplier
+
+    @Test
+    fun testUpdate() = doTest { update { it + 1 } }
+
+    @Test
+    fun testUpdateAndGet() = doTest { updateAndGet { it + 1 } }
+
+    @Test
+    fun testGetAndUpdate() = doTest { getAndUpdate { it + 1 } }
+
+    private fun doTest(increment: MutableStateFlow<Int>.() -> Unit) = runTest {
+        val flow = MutableStateFlow(0)
+        val j1 = launch(Dispatchers.Default) {
+            repeat(iterations / 2) {
+                flow.increment()
+            }
+        }
+
+        repeat(iterations / 2) {
+            flow.increment()
+        }
+
+        joinAll(j1)
+        assertEquals(iterations, flow.value)
+    }
+}