assertInstanceOf methods accept nullable values

Issue: junit-team#1866
awelless · Aug 25, 2023 · 437d29e · 437d29e
1 parent 544b4e1
commit 437d29e
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Showing 2 changed files with 12 additions and 3 deletions.
diff --git a/junit-jupiter-api/src/main/kotlin/org/junit/jupiter/api/Assertions.kt b/junit-jupiter-api/src/main/kotlin/org/junit/jupiter/api/Assertions.kt
@@ -244,7 +244,7 @@ fun assertNotNull(actual: Any?, messageSupplier: () -> String) {
  * @see Assertions.assertInstanceOf
  */
 @API(since = "5.11", status = EXPERIMENTAL)
-inline fun <reified T : Any> assertInstanceOf(actual: Any) {
+inline fun <reified T : Any> assertInstanceOf(actual: Any?) {
     contract {
         returns() implies (actual is T)
     }
@@ -265,7 +265,7 @@ inline fun <reified T : Any> assertInstanceOf(actual: Any) {
  * @see Assertions.assertInstanceOf
  */
 @API(since = "5.11", status = EXPERIMENTAL)
-inline fun <reified T : Any> assertInstanceOf(actual: Any, message: String) {
+inline fun <reified T : Any> assertInstanceOf(actual: Any?, message: String) {
     contract {
         returns() implies (actual is T)
     }
@@ -286,7 +286,7 @@ inline fun <reified T : Any> assertInstanceOf(actual: Any, message: String) {
  * @see Assertions.assertInstanceOf
  */
 @API(since = "5.11", status = EXPERIMENTAL)
-inline fun <reified T : Any> assertInstanceOf(actual: Any, noinline messageSupplier: () -> String) {
+inline fun <reified T : Any> assertInstanceOf(actual: Any?, noinline messageSupplier: () -> String) {
     contract {
         returns() implies (actual is T)
 

diff --git a/junit-jupiter-engine/src/test/kotlin/org/junit/jupiter/api/KotlinAssertionsTests.kt b/junit-jupiter-engine/src/test/kotlin/org/junit/jupiter/api/KotlinAssertionsTests.kt
@@ -236,6 +236,15 @@ class KotlinAssertionsTests {
         assertFalse(string.isEmpty()) // smart cast to a String object
     }
 
+    @Test
+    fun `assertInstanceOf with a null value`() {
+        val error = assertThrows<AssertionFailedError> {
+            assertInstanceOf<String>(null)
+        }
+
+        assertMessageStartsWith(error, "Unexpected null value")
+    }
+
     @Test
     fun `assertDoesNotThrow with value initialization in lambda`() {
         val value: Int