static Collection<String> findIssueKeys(String input) {
        Collection<String> ids = new ArrayList<>();
        Matcher m = PATTERN.matcher(input);
        while (m.find()) {
            if (m.groupCount() >= 1) {
                String issue = m.group(1);
                ids.add(issue.substring(1, issue.length()));
            }
        }
        return ids;
    }
@Test
    public void findIssueKeys() {
        Assert.assertEquals("Find single", Collections.singletonList("123"), GithubIssue.findIssueKeys("Closed #123"));
        Assert.assertEquals("Find multiple", Arrays.asList("123", "143"), GithubIssue.findIssueKeys( "Closed #123 and #143"));
        Assert.assertEquals("Do not find alpha", new ArrayList(), GithubIssue.findIssueKeys( "#AAA"));
    }