Index: trunk/test/unit/org/openstreetmap/josm/data/osm/WaySegmentTest.java
===================================================================
--- trunk/test/unit/org/openstreetmap/josm/data/osm/WaySegmentTest.java	(revision 8990)
+++ trunk/test/unit/org/openstreetmap/josm/data/osm/WaySegmentTest.java	(revision 8990)
@@ -0,0 +1,48 @@
+// License: GPL. For details, see LICENSE file.
+package org.openstreetmap.josm.data.osm;
+
+import java.util.Arrays;
+
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+import org.openstreetmap.josm.JOSMFixture;
+import org.openstreetmap.josm.data.coor.LatLon;
+
+public class WaySegmentTest {
+
+    @Before
+    public void setUp() throws Exception {
+        JOSMFixture.createUnitTestFixture().init();
+    }
+
+    @Test
+    public void testForNodePair() throws Exception {
+        final DataSet ds = new DataSet();
+        final Node n1 = new Node(new LatLon(0, 0));
+        final Node n2 = new Node(new LatLon(1, 0));
+        final Node n3 = new Node(new LatLon(2, 0));
+        final Node n4 = new Node(new LatLon(3, 0));
+        final Way w = new Way();
+        for (OsmPrimitive p : Arrays.asList(n1, n2, n3, n4, w)) {
+            ds.addPrimitive(p);
+        }
+        w.addNode(n1);
+        w.addNode(n2);
+        w.addNode(n1);
+        w.addNode(n3);
+        w.addNode(n1);
+        w.addNode(n4);
+        w.addNode(n1);
+        Assert.assertEquals(WaySegment.forNodePair(w, n1, n2).lowerIndex, 0);
+        Assert.assertEquals(WaySegment.forNodePair(w, n1, n3).lowerIndex, 2);
+        Assert.assertEquals(WaySegment.forNodePair(w, n1, n4).lowerIndex, 4);
+        Assert.assertEquals(WaySegment.forNodePair(w, n4, n1).lowerIndex, 5);
+        try {
+            Assert.assertEquals(WaySegment.forNodePair(w, n3, n4).lowerIndex, 5);
+            throw new IllegalStateException("Expecting IllegalArgumentException");
+        } catch (IllegalArgumentException expected) {
+            // expected
+        }
+    }
+}