Add test cases for ObjectUtils#unwrapOptional

See spring-projectsgh-33618

Author: ngocnhan-tran1996

spring-core/src/test/java/org/springframework/util/ObjectUtilsTests.java

@@ -62,6 +62,7 @@
  * @author Rick Evans
  * @author Sam Brannen
  * @author Hyunjin Choi
+ * @author Ngoc Nhan
  */
 class ObjectUtilsTests {
 
@@ -1114,4 +1115,22 @@ private static String prefix(Class<?> clazz) {
 		}
 	}
 
+	@Test
+	void unwrapOptional() {
+
+		assertThat(ObjectUtils.unwrapOptional(null)).isNull();
+		assertThat(ObjectUtils.unwrapOptional(Optional.empty())).isNull();
+		assertThat(ObjectUtils.unwrapOptional(Optional.of("some value"))).isEqualTo("some value");
+
+		Optional<Optional<Object>> nestedEmptyOptional = Optional.of(Optional.empty());
+		assertThatIllegalArgumentException()
+			.isThrownBy(() -> ObjectUtils.unwrapOptional(nestedEmptyOptional))
+			.withMessage("Multi-level Optional usage not supported");
+
+		Optional<Optional<String>> nestedStringOptional = Optional.of(Optional.of("some value"));
+		assertThatIllegalArgumentException()
+			.isThrownBy(() -> ObjectUtils.unwrapOptional(nestedStringOptional))
+			.withMessage("Multi-level Optional usage not supported");
+	}
+
 }