Update exception message to use correct test class

See gh-35680

spring-test/src/main/java/org/springframework/test/context/bean/override/BeanOverrideTestExecutionListener.java

@@ -95,7 +95,7 @@ public class BeanOverrideTestExecutionListener extends AbstractTestExecutionList
 	private static void injectFields(TestContext testContext) {
 		Object testInstance = testContext.getTestInstance();
 		// Since JUnit Jupiter 5.12, if the SpringExtension is used with Jupiter's
-		// ExtensionContextScope.TEST_METHOD mode, the value returned from
+		// TEST_METHOD ExtensionContextScope, the value returned from
 		// testContext.getTestClass() may refer to the declaring class of the test
 		// method which is about to be invoked (which may be in a @Nested class
 		// within the class for the test instance). Thus, we use the class for the
@@ -109,7 +109,7 @@ public class BeanOverrideTestExecutionListener extends AbstractTestExecutionList
 			Assert.state(applicationContext.containsBean(BeanOverrideRegistry.BEAN_NAME), () -> """
 					Test class %s declares @BeanOverride fields %s, but no BeanOverrideHandler has been registered. \
 					If you are using @ContextHierarchy, ensure that context names for bean overrides match \
-					configured @ContextConfiguration names.""".formatted(testContext.getTestClass().getSimpleName(),
+					configured @ContextConfiguration names.""".formatted(testClass.getSimpleName(),
 							handlers.stream().map(BeanOverrideHandler::getField).filter(Objects::nonNull)
 								.map(Field::getName).toList()));
 			BeanOverrideRegistry beanOverrideRegistry = applicationContext.getBean(BeanOverrideRegistry.BEAN_NAME,