1 files changed, 68 insertions, 0 deletions
diff --git a/kotlinx-coroutines-core/common/test/flow/operators/ScanTest.kt b/kotlinx-coroutines-core/common/test/flow/operators/ScanTest.kt
new file mode 100644
index 00000000..0108ea17
--- /dev/null
+++ b/kotlinx-coroutines-core/common/test/flow/operators/ScanTest.kt
@@ -0,0 +1,68 @@
+/*
+ * Copyright 2016-2019 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 kotlinx.coroutines.channels.*
+import kotlin.test.*
+
+class ScanTest : TestBase() {
+    @Test
+    fun testScan() = runTest {
+        val flow = flowOf(1, 2, 3, 4, 5)
+        val result = flow.scanReduce { acc, v -> acc + v }.toList()
+        assertEquals(listOf(1, 3, 6, 10, 15), result)
+    }
+
+    @Test
+    fun testScanWithInitial() = runTest {
+        val flow = flowOf(1, 2, 3)
+        val result = flow.scan(emptyList<Int>()) { acc, value -> acc + value }.toList()
+        assertEquals(listOf(emptyList(), listOf(1), listOf(1, 2), listOf(1, 2, 3)), result)
+    }
+
+    @Test
+    fun testNulls() = runTest {
+        val flow = flowOf(null, 2, null, null, null, 5)
+        val result = flow.scanReduce { acc, v ->  if (v == null) acc else (if (acc == null) v else acc + v) }.toList()
+        assertEquals(listOf(null, 2, 2, 2, 2, 7), result)
+    }
+
+    @Test
+    fun testEmptyFlow() = runTest {
+        val result = emptyFlow<Int>().scanReduce { _, _ -> 1 }.toList()
+        assertTrue(result.isEmpty())
+    }
+
+    @Test
+    fun testErrorCancelsUpstream() = runTest {
+        expect(1)
+        val latch = Channel<Unit>()
+        val flow = flow {
+            coroutineScope {
+                launch {
+                    latch.send(Unit)
+                    hang { expect(3) }
+                }
+                emit(1)
+                emit(2)
+            }
+        }.scanReduce { _, value ->
+            expect(value) // 2
+            latch.receive()
+            throw TestException()
+        }.catch { /* ignore */ }
+
+        assertEquals(1, flow.single())
+        finish(4)
+    }
+
+    public operator fun <T> Collection<T>.plus(element: T): List<T> {
+        val result = ArrayList<T>(size + 1)
+        result.addAll(this)
+        result.add(element)
+        return result
+    }
+}