return this.map.entryHelper.copy(self(), castForTesting(entry), castForTesting(newNext));
    }

    /** Unsafely sets the value of the given entry. */
    void setValueForTesting(InternalEntry<K, V, ?> entry, V value) {
      this.map.entryHelper.setValue(self(), castForTesting(entry), value);
    }

    /** Unsafely returns a fresh entry. */