Implemented 3353 GitHub issue

documentation/src/docs/asciidoc/release-notes/release-notes-5.10.0-RC1.adoc

@@ -77,5 +77,5 @@ JUnit repository on GitHub.
 * ❓
 
 ==== New Features and Improvements
-
-* ❓
+* New `assertInstanceOf` methods added for Kotlin following up with similar Java `assertInstanceOf`
+methods introduced in `5.8.0` version.

junit-jupiter-api/src/main/kotlin/org/junit/jupiter/api/Assertions.kt

@@ -19,6 +19,7 @@ import org.junit.jupiter.api.function.ThrowingSupplier
 import java.time.Duration
 import java.util.function.Supplier
 import java.util.stream.Stream
+import kotlin.reflect.KClass
 
 /**
  * @see Assertions.fail
@@ -110,6 +111,41 @@ inline fun <reified T : Throwable> assertThrows(executable: () -> Unit): T {
     }
 }
 
+/**
+ * Example usage:
+ * ```kotlin
+ * assertInstanceOf(NotImplementedError(), Error::class)
+ * ```
+ *
+ * @see Assertions.assertInstanceOf
+ */
+@API(status = EXPERIMENTAL, since = "5.10")
+fun assertInstanceOf(source: Any?, type: KClass<*>, message: String = "Provided source object is not of a given type $type") {
+    assert(type.isInstance(source), { message })
+}
+
+/**
+ * Example usage:
+ * ```kotlin
+ * assertThrows<AssertionError> {
+ *     assertInstanceOf({ mapOf(Pair(1, 2)) }, MutableList::class)
+ * }
+ * assertEquals("Talk to a duck", exception.message)
+ * ```
+ * @see Assertions.assertInstanceOf
+ */
+@API(status = EXPERIMENTAL, since = "5.10")
+inline fun assertInstanceOf(
+    sourceSupplier: () -> Any?,
+    type: KClass<*>,
+    message: String = "Provided function yield object that is not an instance of a given type $type"
+) {
+    assert(
+        type.isInstance(sourceSupplier()),
+        { message }
+    )
+}
+
 /**
  * Example usage:
  * ```kotlin

junit-jupiter-engine/src/test/kotlin/org/junit/jupiter/api/KotlinAssertionsTests.kt

@@ -184,6 +184,30 @@ class KotlinAssertionsTests {
         )
     )
 
+    @Test
+    fun `assertInstanceOf test passed`() {
+        assertInstanceOf(NotImplementedError(), Error::class)
+    }
+
+    @Test
+    fun `assertInstanceOf test negative`() {
+        assertThrows<AssertionError> {
+            assertInstanceOf(RuntimeException(), String::class)
+        }
+    }
+
+    @Test
+    fun `assertInstanceOf lazy test passed`() {
+        assertInstanceOf({ mutableListOf(1, 2, 3) }, List::class)
+    }
+
+    @Test
+    fun `assertInstanceOf lazy test negative`() {
+        assertThrows<AssertionError> {
+            assertInstanceOf({ mapOf(Pair(1, 2)) }, MutableList::class)
+        }
+    }
+
     @Test
     fun `assertAll with stream of functions that throw AssertionErrors`() {
         val multipleFailuresError = assertThrows<MultipleFailuresError>("Should have thrown multiple errors") {