commonTest.flow.terminal.SingleTest.kt Maven / Gradle / Ivy

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Coroutines support libraries for Kotlin

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/*
 * 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 kotlin.test.*

class SingleTest : TestBase() {

    @Test
    fun testSingle() = runTest {
        val flow = flow {
            emit(239L)
        }

        assertEquals(239L, flow.single())
        assertEquals(239L, flow.singleOrNull())
    }

    @Test
    fun testMultipleValues() = runTest {
        val flow = flow {
            emit(239L)
            emit(240L)
        }
        assertFailsWith { flow.single() }
        assertNull(flow.singleOrNull())
    }

    @Test
    fun testNoValues() = runTest {
        assertFailsWith { flow {}.single() }
        assertNull(flow {}.singleOrNull())
    }

    @Test
    fun testException() = runTest {
        val flow = flow {
            throw TestException()
        }

        assertFailsWith { flow.single() }
        assertFailsWith { flow.singleOrNull() }
    }

    @Test
    fun testExceptionAfterValue() = runTest {
        val flow = flow {
            emit(1)
            throw TestException()
        }

        assertFailsWith { flow.single() }
        assertFailsWith { flow.singleOrNull() }
    }

    @Test
    fun testNullableSingle() = runTest {
        assertEquals(1, flowOf(1).single())
        assertNull(flowOf(null).single())
        assertFailsWith { flowOf().single() }

        assertEquals(1, flowOf(1).singleOrNull())
        assertNull(flowOf(null).singleOrNull())
        assertNull(flowOf().singleOrNull())
    }

    @Test
    fun testBadClass() = runTest {
        val instance = BadClass()
        val flow = flowOf(instance)
        assertSame(instance, flow.single())
        assertSame(instance, flow.singleOrNull())

        val flow2 = flow {
            emit(BadClass())
            emit(BadClass())
        }
        assertFailsWith { flow2.single() }
    }

    @Test
    fun testSingleNoWait() = runTest {
        val flow = flow {
            emit(1)
            emit(2)
            awaitCancellation()
        }

        assertNull(flow.singleOrNull())
    }
}