Test: Add message to assert

CityDoctorParent/CityDoctorValidation/src/test/java/de/hft/stuttgart/citydoctor2/check/CheckerTest.java

@@ -179,7 +179,7 @@ public class CheckerTest {
         cgmlArch.mountArchive(new ParserConfiguration(8, false));
         ValidationConfiguration config = ValidationConfiguration.loadStandardValidationConfig();
         FeatureCheckedListener l = co -> {
-            assertTrue(co.isValidated());
+            assertTrue("CityObject should be validated", co.isValidated());
         };
         for (CityGmlZipEntry entry : cgmlArch.getEntries()) {
             Checker.streamCheck(entry, null, null, config, l, null);