added a test case

test/src/test/java/hudson/markup/MarkupFormatterTest.java

+/*
+ * The MIT License
+ *
+ * Copyright (c) 2010, CloudBees, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package hudson.markup;
+
+import hudson.security.AuthorizationStrategy.Unsecured;
+import hudson.security.HudsonPrivateSecurityRealm;
+import org.jvnet.hudson.test.HudsonTestCase;
+import org.jvnet.hudson.test.TestExtension;
+import org.kohsuke.stapler.DataBoundConstructor;
+
+import java.io.IOException;
+import java.io.Writer;
+
+/**
+ * @author Kohsuke Kawaguchi
+ */
+public class MarkupFormatterTest extends HudsonTestCase {
+    public void testConfigRoundtrip() throws Exception {
+        hudson.setSecurityRealm(new HudsonPrivateSecurityRealm(false));
+        hudson.setAuthorizationStrategy(new Unsecured());
+        hudson.setMarkupFormatter(new DummyMarkupImpl("hello"));
+        configRoundtrip();
+
+        assertEquals("hello", ((DummyMarkupImpl)hudson.getMarkupFormatter()).prefix);
+    }
+
+    public static class DummyMarkupImpl extends MarkupFormatter {
+        public final String prefix;
+        @DataBoundConstructor
+        public DummyMarkupImpl(String prefix) {
+            this.prefix = prefix;
+        }
+
+        @Override
+        public void translate(String markup, Writer output) throws IOException {
+            output.write(prefix+"["+markup+"]");
+        }
+
+        @TestExtension
+        public static class DescriptorImpl extends MarkupFormatterDescriptor {
+            @Override
+            public String getDisplayName() {
+                return "dummy";
+            }
+        }
+    }
+}

test/src/test/resources/hudson/markup/MarkupFormatterTest/DummyMarkupImpl/config.jelly

+<!-- no config -->
+<j:jelly xmlns:j="jelly:core" xmlns:st="jelly:stapler" xmlns:d="jelly:define" xmlns:l="/lib/layout" xmlns:t="/lib/hudson" xmlns:f="/lib/form">
+  <f:entry field="prefix" title="${%Prefix}">
+    <f:textbox/>
+  </f:entry>
+</j:jelly>