### Question:
TokenIssuerStore { static List<String> guessTokenIssuerUrls(String literal) { if (literal == null) { return Collections.singletonList(null); } final Set<String> issuers = new LinkedHashSet<>(); final Matcher matcher = MATCH_REGEX_GROUP_PATTERN.matcher(literal); if (matcher.matches()) { if (matcher.groupCount() == 1) { for (String groupValue : matcher.group(1).split("\\|")) { issuers.add(literal.substring(0, matcher.start(1) - 1) + groupValue + literal.substring(matcher.end(1) + 1)); } } else if (matcher.groupCount() > 1) { throw new IllegalArgumentException("only one capturing group supported"); } } if (issuers.isEmpty()) { issuers.add(literal); } return issuers.stream().filter(s -> !containsRegex(s)).collect(Collectors.toList()); } private  TokenIssuerStore(ApimAdapterConfig config, RestConfig restConfig, OfflineConfigurationCacheRepo offlineConfigurationCacheRepo); static TokenIssuerStore getInstance(); static TokenIssuerStore init(ApimAdapterConfig config, RestConfig restConfig, OfflineConfigurationCacheRepo offlineConfigurationCacheRepo); static void reset(); Optional<TokenIssuer> resolve(String issuerUrl); Collection<TokenIssuer> getIssuers();  }### Answer:
@Test public void guessTokenIssuerUrls() { assertNull(TokenIssuerStore.guessTokenIssuerUrls(null).get(0)); assertEquals("", TokenIssuerStore.guessTokenIssuerUrls("").get(0)); final List<String> one = TokenIssuerStore.guessTokenIssuerUrls("https: assertEquals(1, one.size()); assertEquals("https: final List<String> oneWithoutGroup = TokenIssuerStore.guessTokenIssuerUrls("https: assertEquals(1, oneWithoutGroup.size()); assertEquals("https: final List<String> three = TokenIssuerStore.guessTokenIssuerUrls("https: assertEquals(3, three.size()); assertEquals("https: assertEquals("https: assertEquals("https: final List<String> oneEmptyGroup = TokenIssuerStore.guessTokenIssuerUrls("https: assertEquals(1, oneEmptyGroup.size()); assertEquals("https: }