Index: applications/editors/josm/plugins/utilsplugin2/src/utilsplugin2/dumbutils/ReplaceGeometryAction.java
===================================================================
--- applications/editors/josm/plugins/utilsplugin2/src/utilsplugin2/dumbutils/ReplaceGeometryAction.java	(revision 27710)
+++ applications/editors/josm/plugins/utilsplugin2/src/utilsplugin2/dumbutils/ReplaceGeometryAction.java	(revision 27750)
@@ -54,12 +54,18 @@
         OsmPrimitive firstObject = selection.get(0);
         OsmPrimitive secondObject = selection.get(1);
-
+        
+        try {
+            replace(firstObject, secondObject);
+        } catch (IllegalArgumentException ex) {
+            JOptionPane.showMessageDialog(Main.parent,
+                    ex.getMessage(), TITLE, JOptionPane.INFORMATION_MESSAGE);
+        }
+         
+    }
+    public void replace(OsmPrimitive firstObject, OsmPrimitive secondObject) {
         if (firstObject instanceof Way && secondObject instanceof Way) {
             replaceWayWithWay(Arrays.asList((Way) firstObject, (Way) secondObject));
         } else if (firstObject instanceof Node && secondObject instanceof Node) {
-            JOptionPane.showMessageDialog(Main.parent,
-                    tr("To replace a node with a node, use the node merge tool."),
-                    TITLE, JOptionPane.INFORMATION_MESSAGE);
-            return;
+            throw new IllegalArgumentException(tr("To replace a node with a node, use the node merge tool."));
         } else if (firstObject instanceof Node) {
             replaceNode((Node) firstObject, secondObject);
@@ -67,8 +73,5 @@
             replaceNode((Node) secondObject, firstObject);
         } else {
-            JOptionPane.showMessageDialog(Main.parent,
-                    tr("This tool can only replace a node with a way, a node with a multipolygon, or a way with a way."),
-                    TITLE, JOptionPane.INFORMATION_MESSAGE);
-            return;
+            throw new IllegalArgumentException(tr("This tool can only replace a node with a way, a node with a multipolygon, or a way with a way."));
         }
     }