*       com.google.common.base.Joiner#skipNulls}.
   * </ul>
   *
   * <p>Note that constructors taking a builder object cannot be tested effectively because
   * semantics of builder can be arbitrarily complex. Still, a factory class can be created in the
   * test to facilitate equality testing. For example:
   *
   * <pre>
   * public class FooTest {
   *
   *   private static class FooFactoryForTest {

   *       com.google.common.base.Joiner#skipNulls}.
   * </ul>
   *
   * <p>Note that constructors taking a builder object cannot be tested effectively because
   * semantics of builder can be arbitrarily complex. Still, a factory class can be created in the
   * test to facilitate equality testing. For example:
   *
   * <pre>
   * public class FooTest {
   *
   *   private static class FooFactoryForTest {