Index: trunk/src/org/openstreetmap/josm/data/validation/TestError.java
===================================================================
--- trunk/src/org/openstreetmap/josm/data/validation/TestError.java	(revision 11335)
+++ trunk/src/org/openstreetmap/josm/data/validation/TestError.java	(revision 11336)
@@ -3,5 +3,4 @@
 
 import java.text.MessageFormat;
-import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
@@ -119,5 +118,5 @@
          */
         public Builder primitives(OsmPrimitive... primitives) {
-            return primitives(new ArrayList<>(Arrays.asList(primitives)));
+            return primitives(Arrays.asList(primitives));
         }
 
@@ -262,5 +261,5 @@
      */
     public Collection<? extends OsmPrimitive> getPrimitives() {
-        return primitives;
+        return Collections.unmodifiableCollection(primitives);
     }
 
@@ -400,5 +399,5 @@
      */
     public Collection<?> getHighlighted() {
-        return highlighted;
+        return Collections.unmodifiableCollection(highlighted);
     }