Index: trunk/test/unit/org/openstreetmap/josm/corrector/ReverseWayTagCorrectorTest.java
===================================================================
--- trunk/test/unit/org/openstreetmap/josm/corrector/ReverseWayTagCorrectorTest.java	(revision 5787)
+++ trunk/test/unit/org/openstreetmap/josm/corrector/ReverseWayTagCorrectorTest.java	(revision 5787)
@@ -0,0 +1,99 @@
+// License: GPL. For details, see LICENSE file.
+package org.openstreetmap.josm.corrector;
+
+import org.junit.Assert;
+import org.junit.BeforeClass;
+import org.junit.Test;
+import org.openstreetmap.josm.Main;
+import org.openstreetmap.josm.data.Preferences;
+import org.openstreetmap.josm.data.osm.Tag;
+
+/**
+ * Unit tests of {@link ReverseWayTagCorrector} class.
+ */
+public class ReverseWayTagCorrectorTest {
+
+    /**
+     * Setup test.
+     */
+    @BeforeClass
+    public static void setUp() {
+        Main.pref = new Preferences();
+    }
+    
+    /**
+     * Test of {@link ReverseWayTagCorrector.TagSwitcher#apply} method.
+     */
+    @Test
+    public void testTagSwitch() {
+        // oneway
+        assertSwitch(new Tag("oneway", "yes"), new Tag("oneway", "-1"));
+        assertSwitch(new Tag("oneway", "true"), new Tag("oneway", "-1"));
+        assertSwitch(new Tag("oneway", "-1"), new Tag("oneway", "yes"));
+        assertSwitch(new Tag("oneway", "no"), new Tag("oneway", "no"));
+        assertSwitch(new Tag("oneway", "something"), new Tag("oneway", "something"));
+        // incline/direction
+        for (String k : new String[]{"incline", "direction"}) {
+            assertSwitch(new Tag(k, "up"), new Tag(k, "down"));
+            assertSwitch(new Tag(k, "down"), new Tag(k, "up"));
+            assertSwitch(new Tag(k, "something"), new Tag(k, "something"));
+        }
+        // :forward/:backward (see #8518)
+        assertSwitch(new Tag("turn:forward", "right"), new Tag("turn:backward", "right"));
+        assertSwitch(new Tag("change:forward", "not_right"), new Tag("change:backward", "not_right"));
+        assertSwitch(new Tag("placement:forward", "right_of:1"), new Tag("placement:backward", "right_of:1"));
+        assertSwitch(new Tag("turn:lanes:forward", "left|right"), new Tag("turn:lanes:backward", "left|right"));
+        assertSwitch(new Tag("change:lanes:forward", "not_right|only_left"), new Tag("change:lanes:backward", "not_right|only_left"));
+        // keys
+        assertSwitch(new Tag("forward", "something"), new Tag("backward", "something"));
+        assertSwitch(new Tag("backward", "something"), new Tag("forward", "something"));
+        assertSwitch(new Tag("up", "something"), new Tag("down", "something"));
+        assertSwitch(new Tag("down", "something"), new Tag("up", "something"));
+        assertSwitch(new Tag("east", "something"), new Tag("west", "something"));
+        assertSwitch(new Tag("west", "something"), new Tag("east", "something"));
+        assertSwitch(new Tag("south", "something"), new Tag("north", "something"));
+        assertSwitch(new Tag("north", "something"), new Tag("south", "something"));
+        // values
+        assertSwitch(new Tag("something", "forward"), new Tag("something", "backward"));
+        assertSwitch(new Tag("something", "backward"), new Tag("something", "forward"));
+        assertSwitch(new Tag("something", "up"), new Tag("something", "down"));
+        assertSwitch(new Tag("something", "down"), new Tag("something", "up"));
+        assertSwitch(new Tag("something", "east"), new Tag("something", "west"));
+        assertSwitch(new Tag("something", "west"), new Tag("something", "east"));
+        assertSwitch(new Tag("something", "south"), new Tag("something", "north"));
+        assertSwitch(new Tag("something", "north"), new Tag("something", "south"));
+        // value[:_]suffix
+        assertSwitch(new Tag("something", "forward:suffix"), new Tag("something", "backward:suffix"));
+        assertSwitch(new Tag("something", "backward_suffix"), new Tag("something", "forward_suffix"));
+        assertSwitch(new Tag("something", "up:suffix"), new Tag("something", "down:suffix"));
+        assertSwitch(new Tag("something", "down_suffix"), new Tag("something", "up_suffix"));
+        assertSwitch(new Tag("something", "east:suffix"), new Tag("something", "west:suffix"));
+        assertSwitch(new Tag("something", "west_suffix"), new Tag("something", "east_suffix"));
+        assertSwitch(new Tag("something", "south:suffix"), new Tag("something", "north:suffix"));
+        assertSwitch(new Tag("something", "north_suffix"), new Tag("something", "south_suffix"));
+        // prefix[:_]value
+        assertSwitch(new Tag("something", "prefix:forward"), new Tag("something", "prefix:backward"));
+        assertSwitch(new Tag("something", "prefix_backward"), new Tag("something", "prefix_forward"));
+        assertSwitch(new Tag("something", "prefix:up"), new Tag("something", "prefix:down"));
+        assertSwitch(new Tag("something", "prefix_down"), new Tag("something", "prefix_up"));
+        assertSwitch(new Tag("something", "prefix:east"), new Tag("something", "prefix:west"));
+        assertSwitch(new Tag("something", "prefix_west"), new Tag("something", "prefix_east"));
+        assertSwitch(new Tag("something", "prefix:south"), new Tag("something", "prefix:north"));
+        assertSwitch(new Tag("something", "prefix_north"), new Tag("something", "prefix_south"));
+        // prefix[:_]value[:_]suffix
+        assertSwitch(new Tag("something", "prefix:forward:suffix"), new Tag("something", "prefix:backward:suffix"));
+        assertSwitch(new Tag("something", "prefix_backward:suffix"), new Tag("something", "prefix_forward:suffix"));
+        assertSwitch(new Tag("something", "prefix:up_suffix"), new Tag("something", "prefix:down_suffix"));
+        assertSwitch(new Tag("something", "prefix_down_suffix"), new Tag("something", "prefix_up_suffix"));
+        assertSwitch(new Tag("something", "prefix:east:suffix"), new Tag("something", "prefix:west:suffix"));
+        assertSwitch(new Tag("something", "prefix_west:suffix"), new Tag("something", "prefix_east:suffix"));
+        assertSwitch(new Tag("something", "prefix:south_suffix"), new Tag("something", "prefix:north_suffix"));
+        assertSwitch(new Tag("something", "prefix_north_suffix"), new Tag("something", "prefix_south_suffix"));
+        // #8499
+        assertSwitch(new Tag("type", "drawdown"), new Tag("type", "drawdown"));
+    }
+    
+    private void assertSwitch(Tag oldTag, Tag newTag) {
+        Assert.assertEquals(ReverseWayTagCorrector.TagSwitcher.apply(oldTag), newTag);
+    }
+}