@Test
public void getExtension() throws Exception {

    assertNull(FilenameUtils.getExtension(null));
    assertNull(FilenameUtils.getExtension(""));
    assertNull(FilenameUtils.getExtension("/b/c"));
    assertNull(FilenameUtils.getExtension("/b.rtl/c"));
    assertEquals("gif", FilenameUtils.getExtension("/b.rtl/c.gif"));
}