new TestStringSetGenerator() {
              @Override
              protected Set<String> create(String[] elements) {
                TestSet<String> inner = new TestSet<>(new HashSet<String>(), null);
                Set<String> outer = Synchronized.set(inner, null);
                inner.mutex = outer;
                Collections.addAll(outer, elements);
                return outer;
              }
            })

            new TestStringSetGenerator() {
              @Override
              protected Set<String> create(String[] elements) {
                TestSet<String> inner = new TestSet<>(new HashSet<String>(), MUTEX);
                Set<String> outer = Synchronized.set(inner, inner.mutex);
                Collections.addAll(outer, elements);
                return outer;
              }
            })
        .named("Synchronized.set")