assertEquals("foo", sb.toString());  sb.append((StringBuffer) null);
    public void testAppend_StringBuffer() {        StrBuilder sb = new StrBuilder();        sb.append(new StringBuffer("foo"));        assertEquals("foo", sb.toString());        sb.append((StringBuffer) null);        assertEquals("foo", sb.toString());        sb.append(new StringBuffer(""));        assertEquals("foo", sb.toString());        sb.append(new StringBuffer("bar"));        assertEquals("foobar", sb.toString());    }