this.refreshes = new LinkedHashSet<>(durations);
    return this;
  }

  @CanIgnoreReturnValue
  CacheBuilderFactory withKeyStrengths(Set<Strength> keyStrengths) {
    this.keyStrengths = new LinkedHashSet<>(keyStrengths);
    Preconditions.checkArgument(!this.keyStrengths.contains(Strength.SOFT));
    return this;
  }

  @CanIgnoreReturnValue
  CacheBuilderFactory withValueStrengths(Set<Strength> valueStrengths) {

        Interners.newBuilder().strong().concurrencyLevel(concurrencyLevel).build();
    InternerImpl<Object> internerImpl = (InternerImpl<Object>) interner;
    assertEquals(Strength.STRONG, internerImpl.map.keyStrength());
  }

  public void testWeak_simplistic() {
    String canonical = "a";
    String not = new String("a");

    Interner<String> pool = Interners.newWeakInterner();

        Interners.newBuilder().strong().concurrencyLevel(concurrencyLevel).build();
    InternerImpl<Object> internerImpl = (InternerImpl<Object>) interner;
    assertEquals(Strength.STRONG, internerImpl.map.keyStrength());
  }

  public void testWeak_simplistic() {
    String canonical = "a";
    String not = new String("a");

    Interner<String> pool = Interners.newWeakInterner();