ReportsRegistry { public static Set<Report> allReports() { return Collections.unmodifiableSet(reports); } private  ReportsRegistry(); static void init(); static Set<Report> allReports(); static Optional<Report> findById(final int id); static Optional<Report> findById(final ReportId reportId);  }
@Test(expected = UnsupportedOperationException.class) public void registryReturnsReadOnlyCollection() { ReportsRegistry.allReports().clear(); }