KOP-2139 Heal XtaClientTest

src/test/java/de/ozgcloud/xta/client/XtaClientTest.java

@@ -79,6 +79,7 @@ class XtaClientTest {
 		@BeforeEach
 		@SneakyThrows
 		void mock() {
+			doReturn(SELF_IDENTIFIER).when(client).deriveIdentifier(SELF_IDENTIFIER_VALUE);
 			when(service.getStatusList(SELF_IDENTIFIER, MAX_LIST_ITEMS)).thenReturn(xtaMessageMetaDataListing);
 			when(config.getMaxListItems()).thenReturn(MAX_LIST_ITEMS);
 		}