@Test
    public void testExtractLinksNone() {
        List<String> links = null;

        links = RegexUtils.extractLinks(null);
        assertNotNull(links);
        assertEquals(0, links.size());

        links = RegexUtils.extractLinks("");
        assertNotNull(links);
        assertEquals(0, links.size());

        links = RegexUtils.extractLinks("Test with no links " + "What about www.google.com");
        assertNotNull(links);
        assertEquals(0, links.size());
    }
Test {@link RegexUtils#extractLinks(String)} with no links.
tika-core/src/test/java/org/apache/tika/utils/RegexUtilsTest.java