### Question:
Utils { public static String getShorterPathIfPrefix(String path1, String path2) { if (!path1.startsWith(path2) && !path2.startsWith(path1)) { return null; } List<String> fragments1 = splitPath(path1); List<String> fragments2 = splitPath(path2); List<String> commonFragments = collectCommonPathFragments(fragments1, fragments2); if (commonFragments.size() != fragments1.size() && commonFragments.size() != fragments2.size()) { return null; } return joinPath(commonFragments); }  static Object getSubdocumentValue(Document document, String key); static Object getSubdocumentValueCollectionAware(Document document, String key); static String getDatabaseNameFromFullName(String fullName); static String getCollectionNameFromFullName(String fullName); static boolean isTrue(Object value); static Number normalizeNumber(Number value); static void markOkay(Document result); static String join(List<?> values, String delimiter); static void changeSubdocumentValue(Object document, String key, Object newValue); static void validateFieldNames(Document document); static Object removeSubdocumentValue(Object document, String key); static String describeType(Object value); static String joinTail(List<String> pathFragments); static String firstFragment(String input); static List<String> splitPath(String input); static String getShorterPathIfPrefix(String path1, String path2); static List<String> collectCommonPathFragments(String path1, String path2); static String getHostName(); static void copySubdocumentValue(Document input, Document result, String key); static final String PATH_DELIMITER; }### Answer:
@Test void testShorterPathIfPrefix() throws Exception { assertThat(Utils.getShorterPathIfPrefix("a", "b")).isNull(); assertThat(Utils.getShorterPathIfPrefix("a.b", "b.c")).isNull(); assertThat(Utils.getShorterPathIfPrefix("a.b.c", "a.b.d")).isNull(); assertThat(Utils.getShorterPathIfPrefix("deleted", "deletedBy")).isNull(); assertThat(Utils.getShorterPathIfPrefix("a.deleted", "a.deletedBy")).isNull(); assertThat(Utils.getShorterPathIfPrefix("a", "a")).isEqualTo("a"); assertThat(Utils.getShorterPathIfPrefix("a.b", "a.b")).isEqualTo("a.b"); assertThat(Utils.getShorterPathIfPrefix("a.b.c", "a")).isEqualTo("a"); assertThat(Utils.getShorterPathIfPrefix("a.b.c", "a.b")).isEqualTo("a.b"); assertThat(Utils.getShorterPathIfPrefix("a.b.c", "a.b.c")).isEqualTo("a.b.c"); }