@Override
 @Test
 public void appendString() {
   StringBuilder appendable = new StringBuilder();
   this.newWith().appendString(appendable);
   Assert.assertEquals("", appendable.toString());
   this.newWith().appendString(appendable, "/");
   Assert.assertEquals("", appendable.toString());
   this.newWith().appendString(appendable, "[", "/", "]");
   Assert.assertEquals("[]", appendable.toString());
   StringBuilder appendable1 = new StringBuilder();
   this.newWith(true).appendString(appendable1);
   Assert.assertEquals("true", appendable1.toString());
   StringBuilder appendable2 = new StringBuilder();
   BooleanIterable iterable = this.newWith(true, false);
   iterable.appendString(appendable2);
   Assert.assertTrue(
       "true, false".equals(appendable2.toString())
           || "false, true".equals(appendable2.toString()));
   StringBuilder appendable3 = new StringBuilder();
   iterable.appendString(appendable3, "/");
   Assert.assertTrue(
       "true/false".equals(appendable3.toString()) || "false/true".equals(appendable3.toString()));
 }