}

  public void testStrong_null() {
    Interner<String> pool = Interners.newStrongInterner();
    assertThrows(NullPointerException.class, () -> pool.intern(null));
  }

  public void testStrong_builder() {
    int concurrencyLevel = 42;
    Interner<Object> interner =
        Interners.newBuilder().strong().concurrencyLevel(concurrencyLevel).build();
    InternerImpl<Object> internerImpl = (InternerImpl<Object>) interner;

  }

  public void testStrong_null() {
    Interner<String> pool = Interners.newStrongInterner();
    assertThrows(NullPointerException.class, () -> pool.intern(null));
  }

  public void testStrong_builder() {
    int concurrencyLevel = 42;
    Interner<Object> interner =
        Interners.newBuilder().strong().concurrencyLevel(concurrencyLevel).build();
    InternerImpl<Object> internerImpl = (InternerImpl<Object>) interner;