Examples for article on Kovenant (#5011)

* Examples of Reflection in Kotlin

* Some article updates to make better use of Assert

* Replaced printlines with log statements

* Added @Ignore to so tests with no assertions

* Examples for Kovenant

* Fixed an issue where tests fail depending on the order they are run

* Test for timeouts on promises

core-kotlin/pom.xml

@@ -55,6 +55,12 @@
             <artifactId>fuel-coroutines</artifactId>
             <version>${fuel.version}</version>
         </dependency>
+        <dependency>
+            <groupId>nl.komponents.kovenant</groupId>
+            <artifactId>kovenant</artifactId>
+            <version>3.3.0</version>
+            <type>pom</type>
+        </dependency>
     </dependencies>
 
     <properties>

core-kotlin/src/test/kotlin/com/baeldung/kotlin/KovenantTest.kt

@@ -0,0 +1,191 @@
+package com.baeldung.kotlin
+
+import nl.komponents.kovenant.*
+import nl.komponents.kovenant.Kovenant.deferred
+import nl.komponents.kovenant.combine.and
+import nl.komponents.kovenant.combine.combine
+import org.junit.Assert
+import org.junit.Before
+import org.junit.Test
+import java.io.IOException
+import java.util.*
+import java.util.concurrent.TimeUnit
+
+class KovenantTest {
+    @Before
+    fun setupTestMode() {
+        Kovenant.testMode { error ->
+            println("An unexpected error occurred")
+            Assert.fail(error.message)
+        }
+    }
+
+    @Test
+    fun testSuccessfulDeferred() {
+        val def = deferred<Long, Exception>()
+        Assert.assertFalse(def.promise.isDone())
+
+        def.resolve(1L)
+        Assert.assertTrue(def.promise.isDone())
+        Assert.assertTrue(def.promise.isSuccess())
+        Assert.assertFalse(def.promise.isFailure())
+    }
+
+    @Test
+    fun testFailedDeferred() {
+        val def = deferred<Long, Exception>()
+        Assert.assertFalse(def.promise.isDone())
+
+        def.reject(RuntimeException())
+        Assert.assertTrue(def.promise.isDone())
+        Assert.assertFalse(def.promise.isSuccess())
+        Assert.assertTrue(def.promise.isFailure())
+    }
+
+    @Test
+    fun testResolveDeferredTwice() {
+        val def = deferred<Long, Exception>()
+        def.resolve(1L)
+        try {
+            def.resolve(1L)
+        } catch (e: AssertionError) {
+            // Expected.
+            // This is slightly unusual. The AssertionError comes from Assert.fail() from setupTestMode()
+        }
+    }
+
+    @Test
+    fun testSuccessfulTask() {
+        val promise = task { 1L }
+        Assert.assertTrue(promise.isDone())
+        Assert.assertTrue(promise.isSuccess())
+        Assert.assertFalse(promise.isFailure())
+    }
+
+    @Test
+    fun testFailedTask() {
+        val promise = task { throw RuntimeException() }
+        Assert.assertTrue(promise.isDone())
+        Assert.assertFalse(promise.isSuccess())
+        Assert.assertTrue(promise.isFailure())
+    }
+
+    @Test
+    fun testCallbacks() {
+        val promise = task { 1L }
+
+        promise.success {
+            println("This was a success")
+            Assert.assertEquals(1L, it)
+        }
+
+        promise.fail {
+            println(it)
+            Assert.fail("This shouldn't happen")
+        }
+
+        promise.always {
+            println("This always happens")
+        }
+    }
+
+    @Test
+    fun testGetValues() {
+        val promise = task { 1L }
+        Assert.assertEquals(1L, promise.get())
+    }
+
+    @Test
+    fun testAllSucceed() {
+        val numbers = all(
+                task { 1L },
+                task { 2L },
+                task { 3L }
+        )
+
+        Assert.assertEquals(listOf(1L, 2L, 3L), numbers.get())
+    }
+
+    @Test
+    fun testOneFails() {
+        val runtimeException = RuntimeException()
+
+        val numbers = all(
+                task { 1L },
+                task { 2L },
+                task { throw runtimeException }
+        )
+
+        Assert.assertEquals(runtimeException, numbers.getError())
+    }
+
+    @Test
+    fun testAnySucceeds() {
+        val promise = any(
+                task {
+                    TimeUnit.SECONDS.sleep(3)
+                    1L
+                },
+                task {
+                    TimeUnit.SECONDS.sleep(2)
+                    2L
+                },
+                task {
+                    TimeUnit.SECONDS.sleep(1)
+                    3L
+                }
+        )
+
+        Assert.assertTrue(promise.isDone())
+        Assert.assertTrue(promise.isSuccess())
+        Assert.assertFalse(promise.isFailure())
+    }
+
+    @Test
+    fun testAllFails() {
+        val runtimeException = RuntimeException()
+        val ioException = IOException()
+        val illegalStateException = IllegalStateException()
+        val promise = any(
+                task {
+                    TimeUnit.SECONDS.sleep(3)
+                    throw runtimeException
+                },
+                task {
+                    TimeUnit.SECONDS.sleep(2)
+                    throw ioException
+                },
+                task {
+                    TimeUnit.SECONDS.sleep(1)
+                    throw illegalStateException
+                }
+        )
+
+        Assert.assertTrue(promise.isDone())
+        Assert.assertFalse(promise.isSuccess())
+        Assert.assertTrue(promise.isFailure())
+    }
+
+    @Test
+    fun testSimpleCombine() {
+        val promise = task { 1L } and task { "Hello" }
+        val result = promise.get()
+
+        Assert.assertEquals(1L, result.first)
+        Assert.assertEquals("Hello", result.second)
+    }
+
+    @Test
+    fun testLongerCombine() {
+        val promise = combine(
+                task { 1L },
+                task { "Hello" },
+                task { Currency.getInstance("USD") }
+        )
+        val result = promise.get()
+
+        Assert.assertEquals(1L, result.first)
+        Assert.assertEquals("Hello", result.second)
+        Assert.assertEquals(Currency.getInstance("USD"), result.third)
+    }
+}

core-kotlin/src/test/kotlin/com/baeldung/kotlin/KovenantTimeoutTest.kt

@@ -0,0 +1,38 @@
+package com.baeldung.kotlin
+
+import nl.komponents.kovenant.Promise
+import nl.komponents.kovenant.any
+import nl.komponents.kovenant.task
+import org.junit.Assert
+import org.junit.Ignore
+import org.junit.Test
+
+@Ignore
+// Note that this can not run in the same test run if KovenantTest has already been executed
+class KovenantTimeoutTest {
+    @Test
+    fun testTimeout() {
+        val promise = timedTask(1000) { "Hello" }
+        val result = promise.get()
+        Assert.assertEquals("Hello", result)
+    }
+
+    @Test
+    fun testTimeoutExpired() {
+        val promise = timedTask(1000) {
+            Thread.sleep(3000)
+            "Hello"
+        }
+        val result = promise.get()
+        Assert.assertNull(result)
+    }
+
+    fun <T> timedTask(millis: Long, body: () -> T) : Promise<T?, List<Exception>> {
+        val timeoutTask = task {
+            Thread.sleep(millis)
+            null
+        }
+        val activeTask = task(body = body)
+        return any(activeTask, timeoutTask)
+    }
+}