Index: /applications/editors/josm/plugins/comfort0/src/net/simon04/comfort0/EditLevel0LAction.java
===================================================================
--- /applications/editors/josm/plugins/comfort0/src/net/simon04/comfort0/EditLevel0LAction.java	(revision 35626)
+++ /applications/editors/josm/plugins/comfort0/src/net/simon04/comfort0/EditLevel0LAction.java	(revision 35627)
@@ -107,9 +107,18 @@
     static List<PrimitiveData> readLevel0(Reader reader, final DataSet dataSet) throws ParseException {
         final List<PrimitiveData> primitives = new Level0LParser(reader).primitives();
-        buildChangeCommands(dataSet, primitives);
+        final SequenceCommand command = buildChangeCommands(dataSet, primitives);
+        GuiHelper.runInEDT(() -> {
+            if (command == null || command.getChildren().isEmpty()) {
+                return;
+            }
+            new Notification(trn(
+                    "Comfort0: Changing {0} primitive",
+                    "Comfort0: Changing {0} primitives", command.getChildren().size(), command.getChildren().size())).show();
+            UndoRedoHandler.getInstance().add(command);
+        });
         return primitives;
     }
 
-    static void buildChangeCommands(DataSet dataSet, List<PrimitiveData> primitives) {
+    static SequenceCommand buildChangeCommands(DataSet dataSet, List<PrimitiveData> primitives) {
         final List<Command> commands = new ArrayList<>();
         for (PrimitiveData fromLevel0L : primitives) {
@@ -132,15 +141,8 @@
             }
         }
-
         if (commands.isEmpty()) {
-            return;
+            return null;
         }
-        final SequenceCommand command = new SequenceCommand("Comfort0", commands);
-        GuiHelper.runInEDT(() -> {
-            new Notification(trn(
-                    "Comfort0: Changing {0} primitive",
-                    "Comfort0: Changing {0} primitives", commands.size(), commands.size())).show();
-            UndoRedoHandler.getInstance().add(command);
-        });
+        return new SequenceCommand("Comfort0", commands);
     }
 }
Index: /applications/editors/josm/plugins/comfort0/test/unit/net/simon04/comfort0/EditLevel0LActionTest.java
===================================================================
--- /applications/editors/josm/plugins/comfort0/test/unit/net/simon04/comfort0/EditLevel0LActionTest.java	(revision 35627)
+++ /applications/editors/josm/plugins/comfort0/test/unit/net/simon04/comfort0/EditLevel0LActionTest.java	(revision 35627)
@@ -0,0 +1,75 @@
+package net.simon04.comfort0;
+
+import static org.CustomMatchers.hasSize;
+import static org.hamcrest.CoreMatchers.instanceOf;
+import static org.hamcrest.CoreMatchers.is;
+import static org.hamcrest.CoreMatchers.nullValue;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+import java.io.StringReader;
+import java.util.List;
+
+import org.junit.Rule;
+import org.junit.Test;
+import org.openstreetmap.josm.command.ChangePropertyCommand;
+import org.openstreetmap.josm.command.PseudoCommand;
+import org.openstreetmap.josm.command.SequenceCommand;
+import org.openstreetmap.josm.data.coor.LatLon;
+import org.openstreetmap.josm.data.osm.DataSet;
+import org.openstreetmap.josm.data.osm.Node;
+import org.openstreetmap.josm.data.osm.PrimitiveData;
+import org.openstreetmap.josm.data.osm.TagMap;
+import org.openstreetmap.josm.testutils.JOSMTestRules;
+
+import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
+
+import net.simon04.comfort0.level0l.parsergen.Level0LParser;
+import net.simon04.comfort0.level0l.parsergen.ParseException;
+
+public class EditLevel0LActionTest {
+
+    /**
+     * Setup rule
+     */
+    @Rule
+    @SuppressFBWarnings(value = "URF_UNREAD_PUBLIC_OR_PROTECTED_FIELD")
+    public JOSMTestRules test = new JOSMTestRules().preferences();
+
+    private SequenceCommand buildChangeCommands(DataSet dataSet) throws ParseException {
+        final String level0l = "node 1831881213: 54.0900666, 12.2539381 #Neu Broderstorf (54.0900666, 12.2539381)\n" +
+                "  name = Neu Broderstorf\n" +
+                "  traffic_sign = city_limit\n";
+        final List<PrimitiveData> primitives = new Level0LParser(new StringReader(level0l)).primitives();
+        return EditLevel0LAction.buildChangeCommands(dataSet, primitives);
+    }
+
+    private ChangePropertyCommand buildChangeCommand(DataSet dataSet) throws ParseException {
+        SequenceCommand commands = buildChangeCommands(dataSet);
+        assertThat(commands.getChildren(), hasSize(1));
+        final PseudoCommand command = commands.getChildren().iterator().next();
+        assertThat(command, instanceOf(ChangePropertyCommand.class));
+        return (ChangePropertyCommand) command;
+    }
+
+    @Test
+    public void test() throws Exception {
+        final Node node = new Node(1831881213, 42);
+        node.setCoor(new LatLon(54.0900666, 12.2539381));
+        final DataSet dataSet = new DataSet(node);
+
+        ChangePropertyCommand command = buildChangeCommand(dataSet);
+        assertThat(command.getTags(), is(new TagMap("name", "Neu Broderstorf", "traffic_sign", "city_limit")));
+
+        node.put("name", "Neu Broderstorf");
+        node.put("traffic_sign", "city_limit");
+        assertThat(buildChangeCommands(dataSet), nullValue());
+
+        node.put("fixme", "delete me!");
+        command = buildChangeCommand(dataSet);
+        assertThat(command.getTags(), is(new TagMap("name", "Neu Broderstorf", "traffic_sign", "city_limit")));
+        node.remove("fixme");
+
+        node.setCoor(new LatLon(55.0900666, 13.2539381));
+        assertThat(buildChangeCommands(dataSet), nullValue()); // TODO
+    }
+}