CharSource source = CharSource.wrap("abcd");
    Iterable<CharSource> cycle = Iterables.cycle(ImmutableList.of(source));
    CharSource concatenated = CharSource.concat(cycle);

    String expected = "abcdabcd";

    // read the first 8 chars manually, since there's no equivalent to ByteSource.slice
    // TODO(cgdecker): Add CharSource.slice?
    StringBuilder builder = new StringBuilder();

     */
    @Test
    public void testSubstringFromLast() throws Exception {
        assertEquals("ab", StringUtil.substringFromLast("abc", "c"));
        assertEquals("abcab", StringUtil.substringFromLast("abcabc", "c"));
        assertEquals("abc", StringUtil.substringFromLast("abc", ""));
        assertEquals("abc", StringUtil.substringFromLast("abc", null));
        assertEquals("abc", StringUtil.substringFromLast("abc", "dddd"));