BAEL-2129 Added Unit test for Void Type in Kotlin article (#5944)

core-kotlin/src/test/kotlin/com/baeldung/voidtypes/VoidTypesUnitTest.kt

@@ -0,0 +1,51 @@
+package com.baeldung.voidtypes
+
+import org.junit.jupiter.api.Test
+import kotlin.test.assertNull
+import kotlin.test.assertTrue
+
+class VoidTypesUnitTest {
+
+    fun returnTypeAsVoid(): Void? {
+        println("Function can have Void as return type")
+        return null
+    }
+
+    fun unitReturnTypeForNonMeaningfulReturns(): Unit {
+        println("No meaningful return")
+    }
+
+    fun unitReturnTypeIsImplicit() {
+        println("Unit Return type is implicit")
+    }
+
+    fun alwaysThrowException(): Nothing {
+        throw IllegalArgumentException()
+    }
+
+    fun invokeANothingOnlyFunction() {
+        alwaysThrowException()
+
+        var name = "Tom"
+    }
+
+    @Test
+    fun givenJavaVoidFunction_thenMappedToKotlinUnit() {
+        assertTrue(System.out.println() is Unit)
+    }
+
+    @Test
+    fun givenVoidReturnType_thenReturnsNullOnly() {
+        assertNull(returnTypeAsVoid())
+    }
+
+    @Test
+    fun givenUnitReturnTypeDeclared_thenReturnsOfTypeUnit() {
+        assertTrue(unitReturnTypeForNonMeaningfulReturns() is Unit)
+    }
+
+    @Test
+    fun givenUnitReturnTypeNotDeclared_thenReturnsOfTypeUnit() {
+        assertTrue(unitReturnTypeIsImplicit() is Unit)
+    }
+}