Index: trunk/test/unit/org/openstreetmap/josm/data/preferences/PreferencesWriterTest.java
===================================================================
--- trunk/test/unit/org/openstreetmap/josm/data/preferences/PreferencesWriterTest.java	(revision 9828)
+++ trunk/test/unit/org/openstreetmap/josm/data/preferences/PreferencesWriterTest.java	(revision 9828)
@@ -0,0 +1,107 @@
+// License: GPL. For details, see LICENSE file.
+package org.openstreetmap.josm.data.preferences;
+
+import static org.junit.Assert.assertEquals;
+
+import java.io.IOException;
+import java.io.PrintWriter;
+import java.io.StringWriter;
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.Map;
+
+import org.junit.Test;
+import org.openstreetmap.josm.data.Version;
+
+/**
+ * Unit tests for class {@link PreferencesWriter}.
+ */
+public class PreferencesWriterTest {
+
+    private static <T extends AbstractSetting<?>> T setting(T s, long time) {
+        s.setTime(time);
+        return s;
+    }
+
+    /**
+     * Unit test of {@link PreferencesWriter#visit(ListListSetting)}.
+     * @throws IOException if any I/O error occurs
+     */
+    @Test
+    public void testListList() throws IOException {
+        try (StringWriter out = new StringWriter(); PreferencesWriter w = new PreferencesWriter(new PrintWriter(out), true, true)) {
+            long time = System.currentTimeMillis() / 1000;
+            w.visit(setting(new ListListSetting(Arrays.asList(Arrays.asList("bar"))), time));
+            assertEquals(String.format(
+                    "  <lists key='null' time='%d'>%n    <list>%n      <entry value='bar'/>%n    </list>%n  </lists>%n", time),
+                    out.toString());
+        }
+    }
+
+    /**
+     * Unit test of {@link PreferencesWriter#visit(ListSetting)}.
+     * @throws IOException if any I/O error occurs
+     */
+    @Test
+    public void testList() throws IOException {
+        try (StringWriter out = new StringWriter(); PreferencesWriter w = new PreferencesWriter(new PrintWriter(out), true, true)) {
+            long time = System.currentTimeMillis() / 1000;
+            w.visit(setting(new ListSetting(Arrays.asList("bar")), time));
+            assertEquals(String.format(
+                    "  <list key='null' time='%d'>%n    <entry value='bar'/>%n  </list>%n", time),
+                    out.toString());
+        }
+    }
+
+    /**
+     * Unit test of {@link PreferencesWriter#visit(MapListSetting)}.
+     * @throws IOException if any I/O error occurs
+     */
+    @Test
+    public void testMapList() throws IOException {
+        try (StringWriter out = new StringWriter(); PreferencesWriter w = new PreferencesWriter(new PrintWriter(out), true, true)) {
+            long time = System.currentTimeMillis() / 1000;
+            Map<String, String> map = new HashMap<>();
+            map.put("foo", "bar");
+            w.visit(setting(new MapListSetting(Arrays.asList(map)), time));
+            assertEquals(String.format(
+                    "  <maps key='null' time='%d'>%n    <map>%n      <tag key='foo' value='bar'/>%n    </map>%n  </maps>%n", time),
+                    out.toString());
+        }
+    }
+
+    /**
+     * Unit test of {@link PreferencesWriter#visit(StringSetting)}.
+     * @throws IOException if any I/O error occurs
+     */
+    @Test
+    public void testString() throws IOException {
+        try (StringWriter out = new StringWriter(); PreferencesWriter w = new PreferencesWriter(new PrintWriter(out), true, true)) {
+            long time = System.currentTimeMillis() / 1000;
+            w.visit(setting(new StringSetting("bar"), time));
+            assertEquals(String.format(
+                    "  <tag key='null' time='%d' value='bar'/>%n", time),
+                    out.toString());
+        }
+    }
+
+    /**
+     * Unit test of {@link PreferencesWriter#write(java.util.Collection)}.
+     * @throws IOException if any I/O error occurs
+     */
+    @Test
+    public void testWrite() throws IOException {
+        try (StringWriter out = new StringWriter(); PreferencesWriter w = new PreferencesWriter(new PrintWriter(out), true, true)) {
+            long time = System.currentTimeMillis() / 1000;
+            Map<String, Setting<?>> map = new HashMap<>();
+            map.put("foo", setting(new StringSetting("bar"), time));
+            w.write(map.entrySet());
+            assertEquals(String.format(
+                    // CHECKSTYLE.OFF: LineLength
+                    "<?xml version=\"1.0\" encoding=\"UTF-8\"?>%n<preferences-defaults xmlns='http://josm.openstreetmap.de/preferences-1.0' xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance' version='%d'>%n  <tag key='foo' time='%d' value='bar'/>%n</preferences-defaults>%n",
+                    // CHECKSTYLE.ON: LineLength
+                    Version.getInstance().getVersion(), time),
+                    out.toString());
+        }
+    }
+}