diff --git a/src/test/java/com/google/gwtexpui/safehtml/client/SafeHtmlBuilderTest.java b/src/test/java/com/google/gwtexpui/safehtml/client/SafeHtmlBuilderTest.java
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+++ b/src/test/java/com/google/gwtexpui/safehtml/client/SafeHtmlBuilderTest.java
@@ -0,0 +1,265 @@
+// Copyright (C) 2009 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gwtexpui.safehtml.client;
+
+import junit.framework.TestCase;
+
+public class SafeHtmlBuilderTest extends TestCase {
+  public void testEmpty() {
+    final SafeHtmlBuilder b = new SafeHtmlBuilder();
+    assertTrue(b.isEmpty());
+    assertFalse(b.hasContent());
+    assertEquals("", b.asString());
+
+    b.append("a");
+    assertTrue(b.hasContent());
+    assertEquals("a", b.asString());
+  }
+
+  public void testToSafeHtml() {
+    final SafeHtmlBuilder b = new SafeHtmlBuilder();
+    b.append(1);
+
+    final SafeHtml h = b.toSafeHtml();
+    assertNotNull(h);
+    assertNotSame(h, b);
+    assertFalse(h instanceof SafeHtmlBuilder);
+    assertEquals("1", h.asString());
+  }
+
+  public void testAppend_boolean() {
+    final SafeHtmlBuilder b = new SafeHtmlBuilder();
+    assertSame(b, b.append(true));
+    assertSame(b, b.append(false));
+    assertEquals("truefalse", b.asString());
+  }
+
+  public void testAppend_char() {
+    final SafeHtmlBuilder b = new SafeHtmlBuilder();
+    assertSame(b, b.append('a'));
+    assertSame(b, b.append('b'));
+    assertEquals("ab", b.asString());
+  }
+
+  public void testAppend_int() {
+    final SafeHtmlBuilder b = new SafeHtmlBuilder();
+    assertSame(b, b.append(4));
+    assertSame(b, b.append(2));
+    assertSame(b, b.append(-100));
+    assertEquals("42-100", b.asString());
+  }
+
+  public void testAppend_long() {
+    final SafeHtmlBuilder b = new SafeHtmlBuilder();
+    assertSame(b, b.append(4L));
+    assertSame(b, b.append(2L));
+    assertEquals("42", b.asString());
+  }
+
+  public void testAppend_float() {
+    final SafeHtmlBuilder b = new SafeHtmlBuilder();
+    assertSame(b, b.append(0.0f));
+    assertEquals("0.0", b.asString());
+  }
+
+  public void testAppend_double() {
+    final SafeHtmlBuilder b = new SafeHtmlBuilder();
+    assertSame(b, b.append(0.0));
+    assertEquals("0.0", b.asString());
+  }
+
+  public void testAppend_String() {
+    final SafeHtmlBuilder b = new SafeHtmlBuilder();
+    assertSame(b, b.append((String) null));
+    assertEquals("", b.asString());
+    assertSame(b, b.append("foo"));
+    assertSame(b, b.append("bar"));
+    assertEquals("foobar", b.asString());
+  }
+
+  public void testAppend_StringBuilder() {
+    final SafeHtmlBuilder b = new SafeHtmlBuilder();
+    assertSame(b, b.append((StringBuilder) null));
+    assertEquals("", b.asString());
+    assertSame(b, b.append(new StringBuilder("foo")));
+    assertSame(b, b.append(new StringBuilder("bar")));
+    assertEquals("foobar", b.asString());
+  }
+
+  public void testAppend_StringBuffer() {
+    final SafeHtmlBuilder b = new SafeHtmlBuilder();
+    assertSame(b, b.append((StringBuffer) null));
+    assertEquals("", b.asString());
+    assertSame(b, b.append(new StringBuffer("foo")));
+    assertSame(b, b.append(new StringBuffer("bar")));
+    assertEquals("foobar", b.asString());
+  }
+
+  public void testAppend_Object() {
+    final SafeHtmlBuilder b = new SafeHtmlBuilder();
+    assertSame(b, b.append((Object) null));
+    assertEquals("", b.asString());
+    assertSame(b, b.append(new Object() {
+      @Override
+      public String toString() {
+        return "foobar";
+      }
+    }));
+    assertEquals("foobar", b.asString());
+  }
+
+  public void testAppend_CharSequence() {
+    final SafeHtmlBuilder b = new SafeHtmlBuilder();
+    assertSame(b, b.append((CharSequence) null));
+    assertEquals("", b.asString());
+    assertSame(b, b.append((CharSequence) "foo"));
+    assertSame(b, b.append((CharSequence) "bar"));
+    assertEquals("foobar", b.asString());
+  }
+
+  public void testAppend_SafeHtml() {
+    final SafeHtmlBuilder b = new SafeHtmlBuilder();
+    assertSame(b, b.append((SafeHtml) null));
+    assertEquals("", b.asString());
+    assertSame(b, b.append(new SafeHtmlString("foo")));
+    assertSame(b, b.append(new SafeHtmlBuilder().append("bar")));
+    assertEquals("foobar", b.asString());
+  }
+
+  public void testHtmlSpecialCharacters() {
+    assertEquals("&amp;", escape("&"));
+    assertEquals("&lt;", escape("<"));
+    assertEquals("&gt;", escape(">"));
+    assertEquals("&quot;", escape("\""));
+    assertEquals("&#39;", escape("'"));
+
+    assertEquals("&amp;", escape('&'));
+    assertEquals("&lt;", escape('<'));
+    assertEquals("&gt;", escape('>'));
+    assertEquals("&quot;", escape('"'));
+    assertEquals("&#39;", escape('\''));
+
+    assertEquals("&lt;b&gt;", escape("<b>"));
+    assertEquals("&amp;lt;b&amp;gt;", escape("&lt;b&gt;"));
+  }
+
+  public void testEntityNbsp() {
+    final SafeHtmlBuilder b = new SafeHtmlBuilder();
+    assertSame(b, b.nbsp());
+    assertEquals("&nbsp;", b.asString());
+  }
+
+  public void testTagBr() {
+    final SafeHtmlBuilder b = new SafeHtmlBuilder();
+    assertSame(b, b.br());
+    assertEquals("<br />", b.asString());
+  }
+
+  public void testTagTableTrTd() {
+    final SafeHtmlBuilder b = new SafeHtmlBuilder();
+    assertSame(b, b.openElement("table"));
+    assertSame(b, b.openTr());
+    assertSame(b, b.openTd());
+    assertSame(b, b.append("d<a>ta"));
+    assertSame(b, b.closeTd());
+    assertSame(b, b.closeTr());
+    assertSame(b, b.closeElement("table"));
+    assertEquals("<table><tr><td>d&lt;a&gt;ta</td></tr></table>", b.asString());
+  }
+
+  public void testTagDiv() {
+    final SafeHtmlBuilder b = new SafeHtmlBuilder();
+    assertSame(b, b.openDiv());
+    assertSame(b, b.append("d<a>ta"));
+    assertSame(b, b.closeDiv());
+    assertEquals("<div>d&lt;a&gt;ta</div>", b.asString());
+  }
+
+  public void testTagAnchor() {
+    final SafeHtmlBuilder b = new SafeHtmlBuilder();
+    assertSame(b, b.openAnchor());
+
+    assertEquals("", b.getAttribute("href"));
+    assertSame(b, b.setAttribute("href", "http://here"));
+    assertEquals("http://here", b.getAttribute("href"));
+    assertSame(b, b.setAttribute("href", "d<a>ta"));
+    assertEquals("d<a>ta", b.getAttribute("href"));
+
+    assertEquals("", b.getAttribute("target"));
+    assertSame(b, b.setAttribute("target", null));
+    assertEquals("", b.getAttribute("target"));
+
+    assertSame(b, b.append("go"));
+    assertSame(b, b.closeAnchor());
+    assertEquals("<a href=\"d&lt;a&gt;ta\">go</a>", b.asString());
+  }
+
+  public void testTagHeightWidth() {
+    final SafeHtmlBuilder b = new SafeHtmlBuilder();
+    assertSame(b, b.openElement("img"));
+    assertSame(b, b.setHeight(100));
+    assertSame(b, b.setWidth(42));
+    assertSame(b, b.closeSelf());
+    assertEquals("<img height=\"100\" width=\"42\" />", b.asString());
+  }
+
+  public void testStyleName() {
+    final SafeHtmlBuilder b = new SafeHtmlBuilder();
+    assertSame(b, b.openSpan());
+    assertSame(b, b.setStyleName("foo"));
+    assertSame(b, b.addStyleName("bar"));
+    assertSame(b, b.append("d<a>ta"));
+    assertSame(b, b.closeSpan());
+    assertEquals("<span class=\"foo bar\">d&lt;a&gt;ta</span>", b.asString());
+  }
+
+  public void testRejectJavaScript_AnchorHref() {
+    final String href = "javascript:window.close();";
+    try {
+      new SafeHtmlBuilder().openAnchor().setAttribute("href", href);
+      fail("accepted javascript in a href");
+    } catch (RuntimeException e) {
+      assertEquals("javascript unsafe in href: " + href, e.getMessage());
+    }
+  }
+
+  public void testRejectJavaScript_ImgSrc() {
+    final String href = "javascript:window.close();";
+    try {
+      new SafeHtmlBuilder().openElement("img").setAttribute("src", href);
+      fail("accepted javascript in img src");
+    } catch (RuntimeException e) {
+      assertEquals("javascript unsafe in href: " + href, e.getMessage());
+    }
+  }
+
+  public void testRejectJavaScript_FormAction() {
+    final String href = "javascript:window.close();";
+    try {
+      new SafeHtmlBuilder().openElement("form").setAttribute("action", href);
+      fail("accepted javascript in form action");
+    } catch (RuntimeException e) {
+      assertEquals("javascript unsafe in href: " + href, e.getMessage());
+    }
+  }
+
+  private static String escape(final char c) {
+    return new SafeHtmlBuilder().append(c).asString();
+  }
+
+  private static String escape(final String c) {
+    return new SafeHtmlBuilder().append(c).asString();
+  }
+}